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==Behavior==
==Behavior==
[[File:Bubo scandiacus Delta 6.jpg|thumb|right|Juvenile owls do not mind associating with one another, especially during winter.]]
[[File:Bubo scandiacus Delta 6.jpg|thumb|right|Juvenile owls do not mind associating with one another, especially during winter.]]
Snowy owls may be active to some extent at both day, from dawn to dusk, and night.<ref name= Konig/><ref name="Manniche" /> Snowy owls have been seen to be active even during the very brief winter daytime in the northern winter.<ref name= Voous/> During the Arctic summer, snowy owls may tend to peak in activity during the twilight that is the darkest time available given the lack of full nightfall.<ref name= Voous/><ref>Young, C.M. (1973). ''The Snowy Owl migration of 1971–72 in the Sudbury region of Ontario''. American Birds 27(1): 11–12.</ref><ref>Shields, M. (1969). ''Activity cycles of Snowy Owls at Barrow, Alaska''. Murrelet 50 (2): 14–16.</ref> Reportedly, the peak time of activity during summer is between 9:00&nbsp;pm and 3:00&nbsp;am in Norway.<ref name= Hagen>Hagen, Y. (1960). ''The Snowy Owl on Hardangervidda in the Summer of 1959''. Papers of The Norwegian State Game Research. 2, No. 7.</ref> The peak time of activity for those owls that once nested on Fetlar was reported between 10:00 and 11:00&nbsp;pm.<ref name= Tulloch>Tulloch, R. J. (1968). ''Snowy Owls breeding in Shetland in 1967''. British Birds 61:119–132.</ref> According to one authority, the least active times are at noon and midnight.<ref name= Watson/> As days become longer near autumn in [[Utqiaġvik, Alaska|Utqiaġvik]], the snowy owls in the tundra become more active around nightfall and can often be seen resting during the day, especially if it is raining.<ref>Shields, M. (1969). ''Activity cycles of Snowy Owls at Barrow, Alaska''. Murrelet 50 (2):14–16.</ref> During winter in [[Alberta]], snowy owls were tracked in the daytime, despite being also active at night (as they were deemed too difficult to track). In the study, they were most active from 8:00–10:00&nbsp;am and 4:00–6:00&nbsp;pm and often rested mostly from 10:00&nbsp;am to 4:00&nbsp;pm. The owls were perched for 98% of observed daylight and seemed to time their activity to peak times for rodents.<ref>Boxall, P. C. & Lein, M. R. (1989). ''Time budgets and activity of wintering Snowy Owls''. Journal of Field Ornithology 60 (1): 20–29.</ref> The variation of activity is probably in correspondence with their primary prey, the [[lemming]]s, and like them, the snowy owl may be considered [[Cathemerality|cathermal]].<ref name= Konig/><ref name= Voous/><ref name="National Geographic">{{cite web|title=Snowy Owl (Nyctea Scandia)|url=http://animals.nationalgeographic.com/animals/birds/snowy-owl/|website=animals.nationalgeographic.com|publisher=National Geographic|date=11 November 2010}}</ref> This species can withstand extremely cold temperatures, having been recorded in temperatures as low as minus 62.5 [[Celsius|degrees Celsius]] with no obvious discomfort and also withstood a 5-hour exposure to minus 93 degrees Celsius but may have struggled with oxygen consumption by the end of this period. The snowy owl has perhaps the second lowest [[thermal conduction]] to the plumage on average of any bird after only the [[Adelie penguin]] (''Pygoscelis adeliae'') and rivals the best insulated mammals, such as [[Dall sheep]] (''Ovis dalli'') and [[Arctic fox]], as the best insulated polar creature.<ref name= Voous/><ref name= Gessaman>Gessaman, J. A. (1972). ''Bioenergetics of the snowy owl (Nyctea scandiaca)''. Arctic and Alpine Research, 4(3), 223–238.</ref><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/condor/v057n06/p0362-p0365.pdf|author=Irving, L. |title=Nocturnal decline in the temperature of birds in cold weather|doi=10.2307/1364794}}</ref> Presumably as many as 7 rodents would need to be eaten daily to survive an extremely cold winter's day.<ref name= Voous/> Adults and young both have been seen to shelter behind rocks to shield themselves from particularly harsh winds or storms.<ref name= Holt/> Snowy owls often spending a majority of time on the ground, perched mostly on a slight rise of elevation.<ref name= Konig/> It has been interpreted from the morphology of their skeletal structure (i.e. their short, broad legs) that snowy owls are not well-suited to perching extensively in trees or rocks and prefer a flat surface to sit upon.<ref name= Potapov/> However, they may perch more so in winter though do so only mainly when hunting, at times on [[hummock]]s, [[Fence]]posts, [[telegraph pole]]s by roads, [[Radio tower|radio]] and [[transmission tower]]s, [[Hay]]stacks, [[chimney]]s and the roofs of houses and large buildings.<ref name= Voous/> Rocks may be used as perches at times in all seasons.<ref name= Voous/> Though often relatively sluggish owls, like most related species, they are capable of sudden dashing movements in various contexts.<ref name= Potapov/> Snowy owls can walk and run quite quickly, using outstretched wings for balance if necessary.<ref name= Konig/> This owl flies with fairly rowing wingbeats, occasionally interrupted by gliding on stretched wings. The flight is fairly buoyant for a ''Bubo'' owl.<ref name= Konig/><ref name= Holt/> When displaying, the male may engage in an undulating flight with interspersed wingbeats and gliding in a slight dihedral, finally dropping rather vertically to the ground.<ref name= Konig/> They are capable for swimming but do not usually do so. Some seen to be swimming were previously injured but young have been seen to swim into water to escape predators if they cannot fly yet. They will also drink when unfrozen water is available.<ref name= Holt/><ref name= Tulloch/><ref>Mebs, T. & Scherzinger, W. (2000). ''Snowy Owl''. In: ''Die eulen Europa: biolgie, kennzeichen, bestande'', edited by T. Mebs and W. Scherzinger, 167–183. Stuttgart: Franckh-Kosmos Verlags-Gmbh and Co.</ref> Snowy owl mothers have been observed to [[Preening (bird)|preen]] their young in the wild, while pairs in captivity have been observed to allopreen.<ref name= Watson/> In the period leading up to breeding, snowy owls switched regularly between searching (for nesting grounds) and loafing, often searching less when snow cover was less extensive.<ref>Therrien, J. F., Pinaud, D., Gauthier, G., Lecomte, N., Bildstein, K. L., & Bety, J. (2015). ''Pre-breeding prospecting behaviour of snowy owls'' (data from Therrien et al. 2015)-reference-data.</ref>
Snowy owls may be active to some extent at both day, from dawn to dusk, and night.<ref name= Konig/> Snowy owls have been seen to be active even during the very brief winter daytime in the northern winter.<ref name= Voous/> During the Arctic summer, snowy owls may tend to peak in activity during the twilight that is the darkest time available given the lack of full nightfall.<ref name= Voous/><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/nab/v027n01/p00011-p00012.pdf|author=Young, C.M. |year=1973|title=The Snowy Owl migration of 1971–72 in the Sudbury region of Ontario|journal= American Birds |volume=27|issue=1|pages= 11–12}}</ref><ref name=shields>{{cite journal|doi=10.2307/3536292}}</ref> Reportedly, the peak time of activity during summer is between 9:00&nbsp;pm and 3:00&nbsp;am in Norway.<ref name= Hagen>Hagen, Y. (1960). ''The Snowy Owl on Hardangervidda in the Summer of 1959''. Papers of The Norwegian State Game Research. 2, No. 7.</ref> The peak time of activity for those owls that once nested on Fetlar was reported between 10:00 and 11:00&nbsp;pm.<ref name= Tulloch>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V61/V61_N03/V61_N03_P119_132_A019.pdf|author=Tulloch, R. J. |year=1968|title=Snowy Owls breeding in Shetland in 1967|journal= British Birds|volume= 61|pages=119–132}}</ref> According to one authority, the least active times are at noon and midnight.<ref name= Watson/> As days become longer near autumn in [[Utqiaġvik, Alaska|Utqiaġvik]], the snowy owls in the tundra become more active around nightfall and can often be seen resting during the day, especially if it is raining.<ref name=shields/> During winter in [[Alberta]], snowy owls were tracked in the daytime, despite being also active at night (as they were deemed too difficult to track). In the study, they were most active during 8:00–10:00&nbsp;am and 4:00–6:00&nbsp;pm and often rested mostly from 10:00&nbsp;am to 4:00&nbsp;pm. The owls were perched for 98% of observed daylight and seemed to time their activity to peak times for rodents.<ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/jfo/v060n01/p0020-p0029.pdf|author1=Boxall, P. C. |author2= Lein, M. R. |year=1989|title=Time budgets and activity of wintering Snowy Owls|journal= Journal of Field Ornithology |volume=60 |issue=1|pages= 20–29}}</ref> The variation of activity is probably in correspondence with their primary prey, the [[lemming]]s, and like them, the snowy owl may be considered [[Cathemerality|cathermal]].<ref name= Konig/><ref name= Voous/><ref name="National Geographic">{{cite web|title=Snowy Owl (Nyctea Scandia)|url=http://animals.nationalgeographic.com/animals/birds/snowy-owl/|website=animals.nationalgeographic.com|publisher=National Geographic|date=11 November 2010}}</ref> This species can withstand extremely cold temperatures, having been recorded in temperatures as low as minus 62.5 [[Celsius|degrees Celsius]] with no obvious discomfort and also withstood a 5-hour exposure to minus 93 degrees Celsius but may have struggled with oxygen consumption by the end of this period. The snowy owl has perhaps the second lowest [[thermal conduction]] to the plumage on average of any bird after only the [[Adelie penguin]] (''Pygoscelis adeliae'') and rivals the best insulated mammals, such as [[Dall sheep]] (''Ovis dalli'') and [[Arctic fox]], as the best insulated polar creature.<ref name= Voous/><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/condor/v057n06/p0362-p0365.pdf|author=Irving, L. |title=Nocturnal decline in the temperature of birds in cold weather|doi=10.2307/1364794}}</ref> Presumably as many as 7 rodents would need to be eaten daily to survive an extremely cold winter's day.<ref name= Voous/> Adults and young both have been seen to shelter behind rocks to shield themselves from particularly harsh winds or storms.<ref name= Holt/> Snowy owls often spending a majority of time on the ground, perched mostly on a slight rise of elevation.<ref name= Konig/> It has been interpreted from the morphology of their skeletal structure (i.e. their short, broad legs) that snowy owls are not well-suited to perching extensively in trees or rocks and prefer a flat surface to sit upon.<ref name= Potapov/> However, they may perch more so in winter though do so only mainly when hunting, at times on [[hummock]]s, [[Fence]]posts, [[telegraph pole]]s by roads, [[Radio tower|radio]] and [[transmission tower]]s, [[Hay]]stacks, [[chimney]]s and the roofs of houses and large buildings.<ref name= Voous/> Rocks may be used as perches at times in all seasons.<ref name= Voous/> Though often relatively sluggish owls, like most related species, they are capable of sudden dashing movements in various contexts.<ref name= Potapov/> Snowy owls can walk and run quite quickly, using outstretched wings for balance if necessary.<ref name= Konig/> This owl flies with fairly rowing wingbeats, occasionally interrupted by gliding on stretched wings. The flight is fairly buoyant for a ''Bubo'' owl.<ref name= Konig/><ref name= Holt/> When displaying, the male may engage in an undulating flight with interspersed wingbeats and gliding in a slight dihedral, finally dropping rather vertically to the ground.<ref name= Konig/> They are capable for swimming but do not usually do so. Some seen to be swimming were previously injured but young have been seen to swim into water to escape predators if they cannot fly yet. They will also drink when unfrozen water is available.<ref name= Holt/><ref name= Tulloch/><ref>Mebs, T. & Scherzinger, W. (2000). ''Snowy Owl''. In: ''Die eulen Europa: biolgie, kennzeichen, bestande'', edited by T. Mebs and W. Scherzinger, 167–183. Stuttgart: Franckh-Kosmos Verlags-Gmbh and Co.</ref> Snowy owl mothers have been observed to [[Preening (bird)|preen]] their young in the wild, while pairs in captivity have been observed to allopreen.<ref name= Watson/> In the period leading up to breeding, snowy owls switched regularly between searching (for nesting grounds) and loafing, often searching less when snow cover was less extensive.<ref>Therrien, J. F., Pinaud, D., Gauthier, G., Lecomte, N., Bildstein, K. L., & Bety, J. (2015). ''Pre-breeding prospecting behaviour of snowy owls'' (data from Therrien et al. 2015)-reference-data.</ref>
[[File:A Snowy Owl in Flight David Hemmings.jpg|thumb|left|Snowy owls are often somewhat ponderous in movements but can be surprisingly and suddenly fast on the wing.]]
[[File:A Snowy Owl in Flight David Hemmings.jpg|thumb|left|Snowy owls are often somewhat ponderous in movements but can be surprisingly and suddenly fast on the wing.]]
Snowy owls will fight with conspecifics in all seasons occasionally but this is relatively infrequent during breeding and rarer still during winter. Dogfights and talon interlocking may ensue if the fight between two snowy owls continues to escalate.<ref name= Evans/><ref name= Watson/><ref name= Taylor/> A study determined that snowy owls are able to orient the whitest parts of their plumage towards the sun, spending about 44% of time oriented as such during sunny days and much less on cloudy days. Some authors interpret this as a presumed signal to conspecifics, but [[thermoregulation]] could also be a factor.<ref>Bortolotti, G. R., Stoffel, M. J., & Galvan, I. (2011). ''Wintering Snowy Owls Bubo scandiacus integrate plumage colour, behaviour and their environment to maximize efficacy of visual displays''. Ibis, 153(1), 134–142.</ref><ref>{{cite journal |author1= Wiebe, K. L. |author2= Chang, A. M. | year=2018| title= ''Seeing sunlit owls in a new light: orienting Snowy Owls may not be displaying.'' | journal=Ibis| volume=160| pages=62–70| doi=10.1111/ibi.12533| issue=1}}</ref> It is known that during winter in Alberta that female snowy owls are territorial towards one another and may not leave an area for up to 80 days but males are nomadic, usually only staying 1–2 days in an area (seldom to 3–17 days). The females spent on average seven times as long in a given area than did males.<ref name= Boxall>Boxall, P.C. & Lein, M.R. (1982). ''Are owls regular? An analysis of pellet regurgitation times of Snowy Owls in the wild''. Raptor Research. 16(3): 79–82.</ref> During threat displays, individuals will lower the front of the body, stretch the head low and forward, with partially extended wings and feathers on the head and raise their back.<ref name= Watson/> If continuously threatened or cornered, the posture in the threat display may become still more contoured and, if pressed, the owl will like back and attempt to slash with its large talons. The threat displays of males are generally more emphatic than those of females.<ref name= Holt/><ref>Kaufman, K. (1996). ''Lives of North American Birds''. Houghton Mifflin Company, Boston & New York.</ref> Although snowy owls have been considered as semi-colonial, they do not appear to fit this mold well. Nesting sites can be loosely clustered but this is a coincidental response to concentrated prey and each pair tends to be somewhat intolerant of each other.<ref name= Holt/><ref name= Hart>Hart, H. C. (1880). ''Notes on the ornithology of the British Polar Expedition, 1875-6''. Zoologist 4:121–129.</ref><ref>Brandt, H. (1942). ''Alaska Bird Trails: An Expedition by Dog Sled to the Delta of the Yukon River at Hooper Bay''. The Bird Research Foundation, Cleveland, OH, USA.</ref><ref>Dorogoi, I.V. (1990). ''[Factors of communal breeding of the Snowy Owls (Nyctea scandiaca) and Anseriformes birds at the Vrangel Island]''. Ornitologiya. 24: 26–33. In Russian with English summary.</ref> During winter, snowy owls are usually solitary but some [[Aggregation (ethology)|aggregation]]s have been recorded, especially nearer the Arctic when more narrow food selection can lead to up to 20–30 owls gathering in an area of about {{convert|20|to|30|ha|acre|abbr=on}}.<ref name= Holt/><ref name= Pitelka2>Pitelka, F. A., Tomich, P. Q. & Treichel, G.W. (1955). ''Ecological relations of jeagers and owls as Lemming predators near Barrow, Alaska''. Ecological Monographs 25: 85–117.</ref> Congregations were also recorded in the winter in Montana, where 31–35 owls wintered in a {{convert|2.6|km2|sqmi|abbr=on}} area, owls mostly grouped in loose aggregations of 5–10 owls each or occasionally side-by-side or about {{convert|20|m|ft|abbr=on}} apart.<ref name= Holt2>Holt, D. W. & Zetterberg, S. A. (2008). ''The 2005 to 2006 Snowy Owl irruption migration to western Montana''. Northwestern Naturalist 89 (3):145–151.</ref> In extreme cases in Utqiaġvik, the owls may have exceptionally close active nests that may be down to only {{convert|800|to|1600|m|ft|abbr=on}} apart.<ref name= Pitelka/> Juvenile males appear to be especially prone to loose associations with one another, appearing to be non-territorial and able to hunt freely in front of one another.<ref name= Holt/> In a {{convert|213|km2|sqmi|abbr=on}} area in and around Utqiaġvik, productive years may have about 54 nests while none may be found in poor years.<ref name= Holt/> Utqiaġvik may have about 5 owls in early summer every {{convert|1.6|km|mi|abbr=on}}, have a nest spacing of {{convert|1.6|to|3.2|km|mi|abbr=on}} and the owls territory size is about {{convert|5.2|to|10.2|km2|sqmi|abbr=on}}.<ref name= Holt/> In [[Churchill, Manitoba]], nest spacing averaged about {{convert|3.2|km|mi|abbr=on}}.<ref name= Shelford>Shelford, V. E. (1943). ''The abundance of the Collared Lemming (Dicrostonyx groenlandicus (TR) VAR. Richardsoni Mer.) in the Churchill area, 1929 to 1940''. Ecology 24 (4):472–484.</ref> In [[Southampton Island]] in a year when the owls nested there, nest spacing averaged {{convert|3.5|km|mi|abbr=on}}, with the closest two {{convert|1|km|mi|abbr=on}} apart and density per nest was {{convert|22|km2|sqmi|abbr=on}}.<ref>Parker, G. R. (1974). ''A population peak and crash of lemmings and Snowy Owls on Southampton Island, Northwest Territories''. Canadian Field-Naturalist. 88(2): 151–156.</ref> In Nunavut, densities could go from 1 owl per {{convert|2.6|km2|sqmi|abbr=on}} in a productive year to 1 owl per {{convert|26|km2|sqmi|abbr=on}} in a poor year and from 36 nests in a {{convert|100|km2|sqmi|abbr=on}} area to none at all.<ref name= Manning>Manning, T. H., Höhn, E. O. & MacPherson, A. H. (1956). ''The birds of Banks Island''. National Museum of Canada Bulletin 143, Biological Series 48.</ref><ref>Vaughn, R. (1992). ''In search of Arctic birds''. London: T & AD Poyser, Ltd.</ref> Owl density on Wrangel Island in Russia was observed be a single bird each {{convert|0.11|to|0.72|km2|sqmi|abbr=on}}.<ref name= Menyushina>Menyushina, I. E. (1997). ''Snowy Owl (Nyctea scandiaca) reproduction in relation to lemming population cycles on Wrangel Island''. In: ''Biology and conservation of owls of the Northern Hemisphere: 2nd International Symposium'', edited by J. R. Duncan, D. H. Johnson and T. H. Nicholls, 572–582. St. Paul: U.S. Dept. of Agriculture, Forest Service, North Central Forest Experiment Station.</ref> The first known study of winter territories took place in [[Horicon Marsh]] where owls ranged from {{convert|0.5|to|2.6|km2|sqmi|abbr=on}} each.<ref name= Keith/> In [[Calgary, Alberta]], mean territory size of juvenile females in winter was {{convert|407.5|ha|acre|abbr=on}} and adult females was {{convert|195.2|ha|acre|abbr=on}}.<ref name= Boxall/> Wintering owls in central Saskatchewan were radio-monitored, determining that 11 males had an average range of {{convert|54.4|km2|sqmi|abbr=on}}, while that of 12 females was {{convert|31.9|km2|sqmi|abbr=on}} with the combined average being {{convert|53.8|km2|sqmi|abbr=on}}.<ref>Chang, A. M., & Wiebe, K. L. (2018). ''Movement patterns and home ranges of male and female Snowy Owls (Bubo scandiacus) wintering on the Canadian prairies''. Canadian Journal of Zoology, 96(6), 545–552.</ref>
Snowy owls will fight with conspecifics in all seasons occasionally but this is relatively infrequent during breeding and rarer still during winter. Dogfights and talon interlocking may ensue if the fight between two snowy owls continues to escalate.<ref name= Evans/><ref name= Watson/><ref name= Taylor/> A study determined that snowy owls are able to orient the whitest parts of their plumage towards the sun, spending about 44% of time oriented as such during sunny days and much less on cloudy days. Some authors interpret this as a presumed signal to conspecifics, but [[thermoregulation]] could also be a factor.<ref>Bortolotti, G. R., Stoffel, M. J., & Galvan, I. (2011). ''Wintering Snowy Owls Bubo scandiacus integrate plumage colour, behaviour and their environment to maximize efficacy of visual displays''. Ibis, 153(1), 134–142.</ref><ref>{{cite journal |author1= Wiebe, K. L. |author2= Chang, A. M. | year=2018| title= ''Seeing sunlit owls in a new light: orienting Snowy Owls may not be displaying.'' | journal=Ibis| volume=160| pages=62–70| doi=10.1111/ibi.12533| issue=1}}</ref> It is known that during winter in Alberta that female snowy owls are territorial towards one another and may not leave an area for up to 80 days but males are nomadic, usually only staying 1–2 days in an area (seldom to 3–17 days). The females spent on average seven times as long in a given area than did males.<ref name= Boxall>Boxall, P.C. & Lein, M.R. (1982). ''Are owls regular? An analysis of pellet regurgitation times of Snowy Owls in the wild''. Raptor Research. 16(3): 79–82.</ref> During threat displays, individuals will lower the front of the body, stretch the head low and forward, with partially extended wings and feathers on the head and raise their back.<ref name= Watson/> If continuously threatened or cornered, the posture in the threat display may become still more contoured and, if pressed, the owl will like back and attempt to slash with its large talons. The threat displays of males are generally more emphatic than those of females.<ref name= Holt/><ref>Kaufman, K. (1996). ''Lives of North American Birds''. Houghton Mifflin Company, Boston & New York.</ref> Although snowy owls have been considered as semi-colonial, they do not appear to fit this mold well. Nesting sites can be loosely clustered but this is a coincidental response to concentrated prey and each pair tends to be somewhat intolerant of each other.<ref name= Holt/><ref name= Hart>Hart, H. C. (1880). ''Notes on the ornithology of the British Polar Expedition, 1875-6''. Zoologist 4:121–129.</ref><ref>Brandt, H. (1942). ''Alaska Bird Trails: An Expedition by Dog Sled to the Delta of the Yukon River at Hooper Bay''. The Bird Research Foundation, Cleveland, OH, USA.</ref><ref>Dorogoi, I.V. (1990). ''[Factors of communal breeding of the Snowy Owls (Nyctea scandiaca) and Anseriformes birds at the Vrangel Island]''. Ornitologiya. 24: 26–33. In Russian with English summary.</ref> During winter, snowy owls are usually solitary but some [[Aggregation (ethology)|aggregation]]s have been recorded, especially nearer the Arctic when more narrow food selection can lead to up to 20–30 owls gathering in an area of about {{convert|20|to|30|ha|acre|abbr=on}}.<ref name= Holt/><ref name= Pitelka2>Pitelka, F. A., Tomich, P. Q. & Treichel, G.W. (1955). ''Ecological relations of jeagers and owls as Lemming predators near Barrow, Alaska''. Ecological Monographs 25: 85–117.</ref> Congregations were also recorded in the winter in Montana, where 31–35 owls wintered in a {{convert|2.6|km2|sqmi|abbr=on}} area, owls mostly grouped in loose aggregations of 5–10 owls each or occasionally side-by-side or about {{convert|20|m|ft|abbr=on}} apart.<ref name= Holt2>Holt, D. W. & Zetterberg, S. A. (2008). ''The 2005 to 2006 Snowy Owl irruption migration to western Montana''. Northwestern Naturalist 89 (3):145–151.</ref> In extreme cases in Utqiaġvik, the owls may have exceptionally close active nests that may be down to only {{convert|800|to|1600|m|ft|abbr=on}} apart.<ref name= Pitelka/> Juvenile males appear to be especially prone to loose associations with one another, appearing to be non-territorial and able to hunt freely in front of one another.<ref name= Holt/> In a {{convert|213|km2|sqmi|abbr=on}} area in and around Utqiaġvik, productive years may have about 54 nests while none may be found in poor years.<ref name= Holt/> Utqiaġvik may have about 5 owls in early summer every {{convert|1.6|km|mi|abbr=on}}, have a nest spacing of {{convert|1.6|to|3.2|km|mi|abbr=on}} and the owls territory size is about {{convert|5.2|to|10.2|km2|sqmi|abbr=on}}.<ref name= Holt/> In [[Churchill, Manitoba]], nest spacing averaged about {{convert|3.2|km|mi|abbr=on}}.<ref name= Shelford>Shelford, V. E. (1943). ''The abundance of the Collared Lemming (Dicrostonyx groenlandicus (TR) VAR. Richardsoni Mer.) in the Churchill area, 1929 to 1940''. Ecology 24 (4):472–484.</ref> In [[Southampton Island]] in a year when the owls nested there, nest spacing averaged {{convert|3.5|km|mi|abbr=on}}, with the closest two {{convert|1|km|mi|abbr=on}} apart and density per nest was {{convert|22|km2|sqmi|abbr=on}}.<ref>Parker, G. R. (1974). ''A population peak and crash of lemmings and Snowy Owls on Southampton Island, Northwest Territories''. Canadian Field-Naturalist. 88(2): 151–156.</ref> In Nunavut, densities could go from 1 owl per {{convert|2.6|km2|sqmi|abbr=on}} in a productive year to 1 owl per {{convert|26|km2|sqmi|abbr=on}} in a poor year and from 36 nests in a {{convert|100|km2|sqmi|abbr=on}} area to none at all.<ref name= Manning>Manning, T. H., Höhn, E. O. & MacPherson, A. H. (1956). ''The birds of Banks Island''. National Museum of Canada Bulletin 143, Biological Series 48.</ref><ref>Vaughn, R. (1992). ''In search of Arctic birds''. London: T & AD Poyser, Ltd.</ref> Owl density on Wrangel Island in Russia was observed be a single bird each {{convert|0.11|to|0.72|km2|sqmi|abbr=on}}.<ref name= Menyushina>Menyushina, I. E. (1997). ''Snowy Owl (Nyctea scandiaca) reproduction in relation to lemming population cycles on Wrangel Island''. In: ''Biology and conservation of owls of the Northern Hemisphere: 2nd International Symposium'', edited by J. R. Duncan, D. H. Johnson and T. H. Nicholls, 572–582. St. Paul: U.S. Dept. of Agriculture, Forest Service, North Central Forest Experiment Station.</ref> The first known study of winter territories took place in [[Horicon Marsh]] where owls ranged from {{convert|0.5|to|2.6|km2|sqmi|abbr=on}} each.<ref name= Keith/> In [[Calgary, Alberta]], mean territory size of juvenile females in winter was {{convert|407.5|ha|acre|abbr=on}} and adult females was {{convert|195.2|ha|acre|abbr=on}}.<ref name= Boxall/> Wintering owls in central Saskatchewan were radio-monitored, determining that 11 males had an average range of {{convert|54.4|km2|sqmi|abbr=on}}, while that of 12 females was {{convert|31.9|km2|sqmi|abbr=on}} with the combined average being {{convert|53.8|km2|sqmi|abbr=on}}.<ref>Chang, A. M., & Wiebe, K. L. (2018). ''Movement patterns and home ranges of male and female Snowy Owls (Bubo scandiacus) wintering on the Canadian prairies''. Canadian Journal of Zoology, 96(6), 545–552.</ref>


===Migration===
===Migration===
It is fair to say that the snowy owl is a partial, if fairly irregular, [[Bird migration|migrant]], having a very broad but patchy wintering range.<ref name= Konig/> 1st year birds tend to disperse farther south in winter than older owls with males wintering usually somewhat more to the south than females of equivalent ages, adult females often wintering the farthest north.<ref name= Voous/><ref name= Scandinavica>Kerlinger, P. & Lein, M.R. (1986). ''Differences in winter range among age-sex classes of Snowy Owls Nyctea scandiaca in North America''. Ornis Scandinavica. 17(1): 1–17.</ref> The snowy owl likely covers more ground than almost any other owl in movements but many complex individual variations are known in movements, and they often do not take the traditional north–south direction that might be assumed.<ref name= Holt/> Migratory movements appear to be somewhat more common in America than in Asia.<ref name= Konig/> A study of wintering owls in the [[Kola Peninsula]] determined that the mean date of arrival of owls was 10 November with a departure date of 13 April, covering an average of {{convert|991|km|mi|abbr=on}} during the course of the wintering period and clustering where [[Ptarmigan|prey]] was more concentrated.<ref>Øien, I. J., Aarvak, T., Jacobsen, K. O., & Solheim, R. (2018). ''Satellite Telemetry Uncovers Important Wintering Areas for Snowy Owls On the Kola Peninsula, Northwestern Russia''. Орнитология, 42, 42–49.</ref> Some variety of movements recorded each autumn and snowy owls winter annually in plains of [[Siberia]] and Mongolia and [[prairie]]s and [[marsh]]lands of Canada.<ref name= Voous/> The [[Great Plains]] area of southern Canada host wintering snowy owls about 2 to 10 times more frequently than other areas of the continent.<ref name= Holt/> Some weak correlation has made with individuals having some level of fealty to certain wintering sites.<ref>Oeming, A. F. (1957). ''Notes on the Barred Owl and the Snowy Owl in Alberta''. Blue Jay 15:153–156.</ref><ref>Follen, D. & Luepke, K. (1980). ''Snowy Owl recaptures''. Inland Bird Banding 52: 60.</ref> Wintering snowy owls, a total of 419, recorded in [[Duluth, Minnesota]] from 1974 to 2012 would occur in larger numbers in years where [[Brown rat|rats]] were more plentiful. The amount of individual returns among 43 Duluth-wintering owls was fairly low in subsequent winters (8 for 1 year, a small handful in the next few years, and 9 in non-consecutive years).<ref name= Holt/> Sometimes surveys appeared to reveal hundreds of wintering snowy owls on coastal sea ice during an irruptive year.<ref name= Voous/><ref name= Marine/> Three siblings that hatched in same nest in [[Cambridge Bay]] were recovered in drastically different spots at least a year later: one in eastern [[Ontario]], one in [[Hudson Bay]] and one in [[Sakhalin Island]].<ref name= Parmelee/> A nestling banded in [[Sogn og Fjordane|Hordaland]] was recovered {{convert|1380|km|mi|abbr=on}} to the northeast in [[Finnmark]].<ref name= Voous/> In the [[Logan Airport]], 17 of 452 owls were recorded to return, eleven the following year, three 2 years later, and then singles variously 6, 10 and 16 years later.<ref name= Holt/> A banded female from Utqiaġvik was recorded to migrate over {{convert|1928|km|mi|abbr=on}} along seacoast down to Russia, returning over {{convert|1528|km|mi|abbr=on}} and covering at least {{convert|3476|km|mi|abbr=on}} in total. Another banded young female from Utqiaġvik went to the same Russian areas, returned to Utqiaġvik and then onto [[Victoria Island (Canada)|Victoria Island]], but did appear to breed, while another also covered a similar route but ended up nesting on [[Banks Island]]. Another female migrated to the [[Canada–United States border]], then moved back to the [[Gulf of Alaska]], then to winter in the same border areas and then finally to both Banks and Victoria Island.<ref name= Holt/><ref name= Fuller/> Snowy owls from the Canadian Arctic were monitored to have covered an average of {{convert|1100|km|mi|abbr=on}} in one autumn then covered an average of {{convert|2900|km|mi|abbr=on}} a year later.<ref name= Therrien2>Therrien, J.-F., Fitzgerald, G., Gauthier G. & Bêty, J. (2011). ''Diet-tissue discrimination factors of carbon and nitrogen stable isotopes in blood of Snowy Owl (Bubo scandiacus)''. Canadian Journal of Zoology 89 (4): 343–347.</ref> In late winter, owls from the same area were found to have covered a mean of {{convert|4093|km|mi|abbr=on}} of ground in the tundra and spent a mean of 108 days, apparently searching for a suitable nesting situation the entire time.<ref>Therrien, J.-F. , Gauthier, G., Pinaud, D. & Bêty, J. (2014). ''Irruptive movements and breeding dispersal of Snowy Owls: a specialized predator exploiting a pulsed resource''. Journal of Avian Biology. 45(6): 536–544.</ref>
It is fair to say that the snowy owl is a partial, if fairly irregular, [[Bird migration|migrant]], having a very broad but patchy wintering range.<ref name= Konig/> 1st year birds tend to disperse farther south in winter than older owls with males wintering usually somewhat more to the south than females of equivalent ages, adult females often wintering the farthest north.<ref name= Voous/><ref name= Scandinavica>Kerlinger, P. & Lein, M.R. (1986). ''Differences in winter range among age-sex classes of Snowy Owls Nyctea scandiaca in North America''. Ornis Scandinavica. 17(1): 1–17.</ref> The snowy owl likely covers more ground than almost any other owl in movements but many complex individual variations are known in movements, and they often do not take the traditional north–south direction that might be assumed.<ref name= Holt/> Migratory movements appear to be somewhat more common in America than in Asia.<ref name= Konig/> A study of wintering owls in the [[Kola Peninsula]] determined that the mean date of arrival of owls was 10 November with a departure date of 13 April, covering an average of {{convert|991|km|mi|abbr=on}} during the course of the wintering period and clustering where [[Ptarmigan|prey]] was more concentrated.<ref>Øien, I. J., Aarvak, T., Jacobsen, K. O., & Solheim, R. (2018). ''Satellite Telemetry Uncovers Important Wintering Areas for Snowy Owls On the Kola Peninsula, Northwestern Russia''. Орнитология, 42, 42–49.</ref> Some variety of movements recorded each autumn and snowy owls winter annually in plains of [[Siberia]] and Mongolia and [[prairie]]s and [[marsh]]lands of Canada.<ref name= Voous/> The [[Great Plains]] area of southern Canada host wintering snowy owls about 2 to 10 times more frequently than other areas of the continent.<ref name= Holt/> Some weak correlation has made with individuals having some level of fealty to certain wintering sites.<ref>Oeming, A. F. (1957). ''Notes on the Barred Owl and the Snowy Owl in Alberta''. Blue Jay 15:153–156.</ref><ref>Follen, D. & Luepke, K. (1980). ''Snowy Owl recaptures''. Inland Bird Banding 52: 60.</ref> Wintering snowy owls, a total of 419, recorded in [[Duluth, Minnesota]] from 1974 to 2012 would occur in larger numbers in years where [[Brown rat|rats]] were more plentiful. The amount of individual returns among 43 Duluth-wintering owls was fairly low in subsequent winters (8 for 1 year, a small handful in the next few years, and 9 in non-consecutive years).<ref name= Holt/> Sometimes surveys appeared to reveal hundreds of wintering snowy owls on coastal sea ice during an irruptive year.<ref name= Voous/><ref name= Marine/> Three siblings that hatched in same nest in [[Cambridge Bay]] were recovered in drastically different spots at least a year later: one in eastern [[Ontario]], one in [[Hudson Bay]] and one in [[Sakhalin Island]].<ref name= Parmelee/> A nestling banded in [[Sogn og Fjordane|Hordaland]] was recovered {{convert|1380|km|mi|abbr=on}} to the northeast in [[Finnmark]].<ref name= Voous/> In the [[Logan Airport]], 17 of 452 owls were recorded to return, eleven the following year, three 2 years later, and then singles variously 6, 10 and 16 years later.<ref name= Holt/> A banded female from Utqiaġvik was recorded to migrate over {{convert|1928|km|mi|abbr=on}} along seacoast down to Russia, returning over {{convert|1528|km|mi|abbr=on}} and covering at least {{convert|3476|km|mi|abbr=on}} in total. Another banded young female from Utqiaġvik went to the same Russian areas, returned to Utqiaġvik and then onto [[Victoria Island (Canada)|Victoria Island]], but did appear to breed, while another also covered a similar route but ended up nesting on [[Banks Island]]. Another female migrated to the [[Canada–United States border]], then moved back to the [[Gulf of Alaska]], then to winter in the same border areas and then finally to both Banks and Victoria Island.<ref name= Holt/> Snowy owls from the Canadian Arctic were monitored to have covered an average of {{convert|1100|km|mi|abbr=on}} in one autumn then covered an average of {{convert|2900|km|mi|abbr=on}} a year later.<ref name= Therrien2>Therrien, J.-F., Fitzgerald, G., Gauthier G. & Bêty, J. (2011). ''Diet-tissue discrimination factors of carbon and nitrogen stable isotopes in blood of Snowy Owl (Bubo scandiacus)''. Canadian Journal of Zoology 89 (4): 343–347.</ref> In late winter, owls from the same area were found to have covered a mean of {{convert|4093|km|mi|abbr=on}} of ground in the tundra and spent a mean of 108 days, apparently searching for a suitable nesting situation the entire time.<ref>Therrien, J.-F. , Gauthier, G., Pinaud, D. & Bêty, J. (2014). ''Irruptive movements and breeding dispersal of Snowy Owls: a specialized predator exploiting a pulsed resource''. Journal of Avian Biology. 45(6): 536–544.</ref>


In no fewer than 24 winters between 1882 and 1988, large numbers have occurred in Canada and the United States. These were [[Irruptive growth|irruption]] years.<ref name= Voous/> Record breeding irruptive years were recorded in the winters of 2011–2012 and 2014–2015.<ref name= Holt/><ref>Jorgensen, J. G., Dinan, L. R., & Walker Jr, T. J. (2012). ''Snowy Owl Invasion of 2011–12''.</ref> In the 1940s, it was calculated that the mean gape in time between large irruptions was 3.9 years.<ref name= Gross1/> Southbound movements as such are much more conspicuous after peak vole years, once thought to be separated by periods of around 3–7 years.<ref name= Voous/><ref>Snyder, L. L. (1943). ''The Snowy Owl migration of 1941–42''. Wilson Bulletin 55 (1):8–10.</ref><ref>Shelford, V. E. (1945). ''The relation of Snowy Owl migration to the abundance of the Collared Lemming''. Auk 62 (4):592–596.</ref><ref>Chitty, H. (1950). ''Canadian Arctic wild life enquiry, 1943–1949: With a summary of results since 1933''. Journal of Animal Ecology 19 (2):180–193.</ref><ref name="Godfrey" /> However, more extensive research has weakened the argument that irruptions are entirely food-based and the data indicates that irruptive movements are far from predictable. This is because a statewide survey in Alaska found no statewide synchrony in lemming numbers. Therefore, rather than decline of lemmings, it is the successful productivity of several pairs that plays the role, resulting in a large number of young owls that then irrupt. However, the snowy owls cannot breed in high numbers unless lemmings are widely available on the tundra.<ref name= Holt/><ref name= Kerlinger2/><ref name= Gross/><ref>Pitelka, F. A. & Batzli, G. O. (1993). ''Distribution, abundance, and habitat use by lemmings on the north slope of Alaska''. In: ''The biology of lemmings'', edited by N. C. Stenseth and R. A. Ims, 213–236. London: Academic Press.</ref><ref name="Krebs">Krebs, C. J. (1993). ''Are lemmings large Microtus or small reindeer? A review of lemming cycles after 25 years and future recommendations for future work''. In: ''The biology of lemmings'', edited by N. C. Stenseth and R. Ims, 247–260. London: Academic Press for the Linnean Society of London.</ref> This connection of irruptions to high years of productivity was confirmed in a study by Robillard et al. (2016).<ref>Robillard, A., Therrien, J. F., Gauthier, G., Clark, K. M., & Bêty, J. (2016). ''Pulsed resources at tundra breeding sites affect winter irruptions at temperate latitudes of a top predator, the snowy owl''. Oecologia, 181(2), 423–433.</ref> About 90% of the snowy owls seen in irruptive years from 1991 to 2016 that were ageable were identified as juveniles.<ref name= Santonja/>
In no fewer than 24 winters between 1882 and 1988, large numbers have occurred in Canada and the United States. These were [[Irruptive growth|irruption]] years.<ref name= Voous/> Record breeding irruptive years were recorded in the winters of 2011–2012 and 2014–2015.<ref name= Holt/> In the 1940s, it was calculated that the mean gape in time between large irruptions was 3.9 years.<ref name= Gross1/> Southbound movements as such are much more conspicuous after peak vole years, once thought to be separated by periods of around 3–7 years.<ref name= Voous/><ref>{{cite journal|author=Snyder, L. L. |year=1943|title=The Snowy Owl migration of 1941–42|journal= Wilson Bulletin |volume=55 |issue=1|pages=8–10|jstor=4157203|url=https://sora.unm.edu/sites/default/files/journals/wilson/v055n01/p0008-p0010.pdf}}</ref><ref>{{cite journal|doi=10.2307/4079810}}</ref><ref name=chitty/> However, more extensive research has weakened the argument that irruptions are entirely food-based and the data indicates that irruptive movements are far from predictable. This is because a statewide survey in Alaska found no statewide synchrony in lemming numbers. Therefore, rather than decline of lemmings, it is the successful productivity of several pairs that plays the role, resulting in a large number of young owls that then irrupt. However, the snowy owls cannot breed in high numbers unless lemmings are widely available on the tundra.<ref name= Holt/><ref name= Kerlinger2/><ref name= Gross/><ref>Pitelka, F. A. & Batzli, G. O. (1993). ''Distribution, abundance, and habitat use by lemmings on the north slope of Alaska''. In: ''The biology of lemmings'', edited by N. C. Stenseth and R. A. Ims, 213–236. London: Academic Press.</ref><ref name="Krebs">Krebs, C. J. (1993). ''Are lemmings large Microtus or small reindeer? A review of lemming cycles after 25 years and future recommendations for future work''. In: ''The biology of lemmings'', edited by N. C. Stenseth and R. Ims, 247–260. London: Academic Press for the Linnean Society of London.</ref> This connection of irruptions to high years of productivity was confirmed in a study by Robillard et al. (2016).<ref>{{cite journal|pmid=26920901|doi=10.1007/s00442-016-3588-3}}</ref> About 90% of the snowy owls seen in irruptive years from 1991 to 2016 that were ageable were identified as juveniles.<ref name= Santonja/>


==Feeding==
==Feeding==
===Hunting techniques===
===Hunting techniques===
[[File:Harfang en vol 1.jpg|thumb|right|A snowy owl engaging in the "sweep" hunting method.]]
[[File:Harfang en vol 1.jpg|thumb|right|A snowy owl engaging in the "sweep" hunting method.]]
Snowy owls may hunt at nearly at any time of the day or night, but may not attempt to do so during particularly severe weather.<ref name= Holt/> During the [[summer solstice]], the owls appear to hunt during "theoretical nightfall".<ref name= Holt/> [[Night-vision device]]s have allowed biologists to observe that snowy owls hunt quite often during the extended nighttime during the northern winter.<ref name= Potapov/><ref name= Holt/><ref name="Manniche" /> Prey are both taken and eaten on the ground.<ref name= Konig/> Snowy owls, like other carnivorous birds, often swallow their small prey whole.<ref name= Konig/> Strong stomach juices digest the flesh, while the indigestible bones, teeth, fur, and feathers are compacted into oval pellets that the bird regurgitates 18 to 24 hours after feeding. Regurgitation often takes place at regular perches, where dozens of pellets may be found. Biologists frequently examine these pellets to determine the quantity and types of prey the birds have eaten. When large prey are eaten in small pieces, pellets will not be produced.<ref>[http://www.owlpages.com/owls.php?genus=Bubo&species=scandiacus Snowy Owl — ''Bubo scandiacus'', formerly ''Nyctea scandiaca'']. owlpages.com</ref> Larger prey is often torn apart, sometimes include removal of the head, with the large muscles, such as the [[humerus]] or [[Thorax|breast]], typically eaten first.<ref name= Holt/> The scattering of remains that results from the increment feeding on larger prey is thought to result in under-identification of them compared to smaller prey items.<ref>{{cite journal|title=A taphonomic investigation of small vertebrate accumulations produced by the snowy owl (''Bubo scandiacus'') and its implications for fossil studies|doi=10.1016/j.palaeo.2018.10.018}}</ref> The aptitude for hunting by day, hunting from the ground and hunting in almost always completely open and treeless areas are the primary ways in which the snowy owl differs in hunting from other ''Bubo'' owls. Otherwise, the hunting habits are similar.<ref name= Holt/><ref name= Johnsgard>[[Paul Johnsgard|Johnsgard, P. A.]] (1988). [https://digitalcommons.unl.edu/johnsgard/46/ ''North American owls: biology and natural history'']. Smithsonian Institution.</ref> It is thought, due to their less refined hearing compared to other owls, prey is usually perceived via vision and movement.<ref name= Voous/><ref name= Holt/> Experiments indicate that snowy owls can detect prey from as far as {{convert|1.6|km|mi|abbr=on}} away.<ref name= Smith/> Snowy owls generally use a rise or, occasionally, a perch while hunting.<ref name= Konig/> 88% of observed 34 hunts in Utqiaġvik were undertaken from an elevated watch-site (56% mounds or rises, 37% [[telephone pole]]s).<ref name= Holt/> Their hunting style may recall that of [[Buteo|buzzard]]s, with the hunting owl sitting rather low and perching immobile for a long spell.<ref name= Hume/> Although their usual flight is a slow, deliberate downbeat on the broad, fingered wings, when prey is detected from their perch, flight may undertaken with a sudden, surprisingly quick accelerated style with interspersed wing beats.<ref name= Hume/><ref>{{cite journal|author=Hohn, E. O. |year=1973|title=Winter hunting of Snowy Owls in farmland|journal= Canadian Field-Naturalist|volume= 87 |issue=4|pages= 468–469}}</ref> In Utqiaġvik, snowy owls may most frequently engage in a brief pursuit hunting style.<ref name= Holt/> In high winds capable of keeping their bulk aloft, snowy owls may too engage in a brief [[Levitation|hovering]] flight before dropping onto prey.<ref name= Watson/> When hunting fish, apparently, some snowy owls will hover in a style reminiscent of the [[osprey]] (''Pandion haliaetus''), although in at least one other case a snowy owl was observed to capture fish by lying on its belly upon a rock by a fishing hole.<ref name= Audubon>Audubon, J. J. (1840). ''The Birds of America''. Dover Publications, Inc., New York, NY, USA.</ref> A dashing stoop or pounce down onto their prey, ending in a high-impact "wallop", is fairly commonly recorded.<ref name= Holt/><ref name= Hume/> Another common technique is the "sweep", wherein they fly by and grasp the prey while continuing to fly.<ref name= Holt/><ref>{{cite journal|author=Dancey, H.E. |year=1983|title=Winter foraging habits of a Snowy Owl|journal= Indiana Audubon Quarterly|volume= 61|issue=4|pages= 136–144}}</ref> In winter, snowy owls have been shown to be able to "snow plunge" to capture prey in the [[Subnivean climate|subnivean zone]], under at least {{convert|20|cm|in|abbr=on}} of snow.<ref name= Smith/> Perhaps least frequently, snowy owls may pursue their on foot, in doing so never taking wing.<ref name= Holt/> Snowy owls have been known to capture [[Bird migration|night-migrating]] [[passerine]]s and [[shorebird]]s, sometimes perhaps on the wing, as well as large and/or [[Bird of prey|potentially dangerous]] birds that were caught in air by snowy owls during daylight.<ref name= Holt/> On the wing pursuits against other various other carnivorous birds are sometimes undertaken as well to [[Kleptoparasitism|kleptoparasitize]] the prey caught by the other birds.<ref name= Holt/><ref>Duffy, D. C., Beehler B. & Haas, W. (1976). ''Snowy Owl steals prey from Marsh Hawk''. Auk 93 (4): 839–840.</ref> Few variations of hunting technique were observed in winter observations from [[Alberta]], almost all of the hunts being with the sit-and-wait method (also known as still-hunts). Adult females in Alberta had a considerably better hunting rate than juvenile females.<ref name= Boxall2>{{cite journal|doi=10.14430/arctic2326|title=Feeding ecology of Snowy Owls (''Nyctea scandiaca'') wintering in S. Alberta}}</ref> Much as in Alberta, in [[Syracuse, New York]], 90% of 51 hunts were still-hunting, with the sweep variant used after perch departure in 31% of hunts and the pounce method in 45% of hunts. The Syracuse-wintering owls used tall perches, a mixture of manmade objects and trees of around {{convert|6|m|ft|abbr=on}} high, in nearly 61% of hunts, while nearly 14% were from low perches (i.e. fence-posts, snow banks and scrap piles) about half as high as the tall perches and started from a ground position nearly 10% of the time.<ref name= Winter>Winter, R. E. (2016). ''Hunting Behaviors and Foraging Success of Winter Irruptive Snowy Owls in New York''. SUNY College of Environmental Science and Forestry, Thesis.</ref> In Sweden, males hunted from a perch more so than did females and adults both focused on significantly smaller prey (small [[mammal]]s) and may have had more success hunting than juvenile snowy owls.<ref name= Lind/> Some snowy owls can survive a fast for up to about 40 days off of [[Fatty acid metabolism|fat reserves]].<ref name= Hume/> These owls were found to have extremely thick [[Subcutaneous tissue|subcutaneous fat deposits]] of around {{convert|19|to|22|mm|in|abbr=on}} and it is likely owls that overwinter in the Arctic rely heavily on these to survive during this scarce time, in combination with lethargic, energy-conserving behavior.
Snowy owls may hunt at nearly at any time of the day or night, but may not attempt to do so during particularly severe weather.<ref name= Holt/> During the [[summer solstice]], the owls appear to hunt during "theoretical nightfall".<ref name= Holt/> [[Night-vision device]]s have allowed biologists to observe that snowy owls hunt quite often during the extended nighttime during the northern winter.<ref name= Potapov/><ref name= Holt/> Prey are both taken and eaten on the ground.<ref name= Konig/> Snowy owls, like other carnivorous birds, often swallow their small prey whole.<ref name= Konig/> Strong stomach juices digest the flesh, while the indigestible bones, teeth, fur, and feathers are compacted into oval pellets that the bird regurgitates 18 to 24 hours after feeding. Regurgitation often takes place at regular perches, where dozens of pellets may be found. Biologists frequently examine these pellets to determine the quantity and types of prey the birds have eaten. When large prey are eaten in small pieces, pellets will not be produced.<ref>[http://www.owlpages.com/owls.php?genus=Bubo&species=scandiacus Snowy Owl — ''Bubo scandiacus'', formerly ''Nyctea scandiaca'']. owlpages.com</ref> Larger prey is often torn apart, sometimes include removal of the head, with the large muscles, such as the [[humerus]] or [[Thorax|breast]], typically eaten first.<ref name= Holt/> The scattering of remains that results from the increment feeding on larger prey is thought to result in under-identification of them compared to smaller prey items.<ref>{{cite journal|title=A taphonomic investigation of small vertebrate accumulations produced by the snowy owl (''Bubo scandiacus'') and its implications for fossil studies|doi=10.1016/j.palaeo.2018.10.018}}</ref> The aptitude for hunting by day, hunting from the ground and hunting in almost always completely open and treeless areas are the primary ways in which the snowy owl differs in hunting from other ''Bubo'' owls. Otherwise, the hunting habits are similar.<ref name= Holt/><ref name= Johnsgard>[[Paul Johnsgard|Johnsgard, P. A.]] (1988). [https://digitalcommons.unl.edu/johnsgard/46/ ''North American owls: biology and natural history'']. Smithsonian Institution.</ref> It is thought, due to their less refined hearing compared to other owls, prey is usually perceived via vision and movement.<ref name= Voous/><ref name= Holt/> Experiments indicate that snowy owls can detect prey from as far as {{convert|1.6|km|mi|abbr=on}} away. Snowy owls generally use a rise or, occasionally, a perch while hunting.<ref name= Konig/> 88% of observed 34 hunts in Utqiaġvik were undertaken from an elevated watch-site (56% mounds or rises, 37% [[telephone pole]]s).<ref name= Holt/> Their hunting style may recall that of [[Buteo|buzzard]]s, with the hunting owl sitting rather low and perching immobile for a long spell.<ref name= Hume/> Although their usual flight is a slow, deliberate downbeat on the broad, fingered wings, when prey is detected from their perch, flight may undertaken with a sudden, surprisingly quick accelerated style with interspersed wing beats.<ref name= Hume/><ref>{{cite journal|author=Hohn, E. O. |year=1973|title=Winter hunting of Snowy Owls in farmland|journal= Canadian Field-Naturalist|volume= 87 |issue=4|pages= 468–469}}</ref> In Utqiaġvik, snowy owls may most frequently engage in a brief pursuit hunting style.<ref name= Holt/> In high winds capable of keeping their bulk aloft, snowy owls may too engage in a brief [[Levitation|hovering]] flight before dropping onto prey.<ref name= Watson/> When hunting fish, apparently, some snowy owls will hover in a style reminiscent of the [[osprey]] (''Pandion haliaetus''), although in at least one other case a snowy owl was observed to capture fish by lying on its belly upon a rock by a fishing hole.<ref name= Audubon>Audubon, J. J. (1840). ''The Birds of America''. Dover Publications, Inc., New York, NY, USA.</ref> A dashing stoop or pounce down onto their prey, ending in a high-impact "wallop", is fairly commonly recorded.<ref name= Holt/><ref name= Hume/> Another common technique is the "sweep", wherein they fly by and grasp the prey while continuing to fly.<ref name= Holt/><ref>{{cite journal|author=Dancey, H.E. |year=1983|title=Winter foraging habits of a Snowy Owl|journal= Indiana Audubon Quarterly|volume= 61|issue=4|pages= 136–144}}</ref> In winter, snowy owls have been shown to be able to "snow plunge" to capture prey in the [[Subnivean climate|subnivean zone]], under at least {{convert|20|cm|in|abbr=on}} of snow. Perhaps least frequently, snowy owls may pursue their on foot, in doing so never taking wing.<ref name= Holt/> Snowy owls have been known to capture [[Bird migration|night-migrating]] [[passerine]]s and [[shorebird]]s, sometimes perhaps on the wing, as well as large and/or [[Bird of prey|potentially dangerous]] birds that were caught in air by snowy owls during daylight.<ref name= Holt/> On the wing pursuits against other various other carnivorous birds are sometimes undertaken as well to [[Kleptoparasitism|kleptoparasitize]] the prey caught by the other birds.<ref name= Holt/><ref>Duffy, D. C., Beehler B. & Haas, W. (1976). ''Snowy Owl steals prey from Marsh Hawk''. Auk 93 (4): 839–840.</ref> Few variations of hunting technique were observed in winter observations from [[Alberta]], almost all of the hunts being with the sit-and-wait method (also known as still-hunts). Adult females in Alberta had a considerably better hunting rate than juvenile females.<ref name= Boxall2>{{cite journal|doi=10.14430/arctic2326|title=Feeding ecology of Snowy Owls (''Nyctea scandiaca'') wintering in S. Alberta}}</ref> Much as in Alberta, in [[Syracuse, New York]], 90% of 51 hunts were still-hunting, with the sweep variant used after perch departure in 31% of hunts and the pounce method in 45% of hunts. The Syracuse-wintering owls used tall perches, a mixture of manmade objects and trees of around {{convert|6|m|ft|abbr=on}} high, in nearly 61% of hunts, while nearly 14% were from low perches (i.e. fence-posts, snow banks and scrap piles) about half as high as the tall perches and started from a ground position nearly 10% of the time.<ref name= Winter>Winter, R. E. (2016). ''Hunting Behaviors and Foraging Success of Winter Irruptive Snowy Owls in New York''. SUNY College of Environmental Science and Forestry, Thesis.</ref> In Sweden, males hunted from a perch more so than did females and adults both focused on significantly smaller prey (small [[mammal]]s) and may have had more success hunting than juvenile snowy owls.<ref name= Lind/> Some snowy owls can survive a fast for up to about 40 days off of [[Fatty acid metabolism|fat reserves]].<ref name= Hume/> These owls were found to have extremely thick [[Subcutaneous tissue|subcutaneous fat deposits]] of around {{convert|19|to|22|mm|in|abbr=on}} and it is likely owls that overwinter in the Arctic rely heavily on these to survive during this scarce time, in combination with lethargic, energy-conserving behavior.


Snowy owls may not infrequently exploit prey inadvertently provided or compromised by human activities, including ducks injured by [[Hunting|duck hunters]], [[Red phalarope|birds]] maimed by [[Antenna (radio)|antenna]] wires, various animals caught in human [[Trapping|traps]] and [[trapline]]s as well as [[Domestication of animals|domestic]] or wild prey being bred or farmed by humans in enclosures.<ref name= Watson/><ref name=Wiggins/><ref>Brooks, W. S. (1915). ''Notes on birds from east Siberia and Arctic Alaska''. Bulletin of the Museum of Comparative Zoology 59:361–413.</ref><ref>Nagell, B. & Frycklund, I. (1965). ''The irruption of the Snowy Owl (Nyctea scandiaca) in Scandinavia in the winters of 1960–1963 and notes on its behavior''. Vår Fågelvärld 24 (1): 26–55.</ref><ref>King, B., Nayler, F. & Wardle, F. (1966). ''Feeding and resting behavior of a Snowy Owl in Scilly''. British Birds 59 (3): 108.</ref><ref name= Robertson>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/jrr/v037n02/p00164-p00166.pdf|author1=Robertson, G. J. |author2=Gilchrist, H. G. |year=2003|title=Wintering Snowy Owls feed on sea ducks in the Belcher Islands, Nunavut, Canada|journal= Journal of Raptor Research |volume=37 |issue=2|pages= 164–166}}</ref> A wide variety of accrued reports show that the snowy owl that [[Scavenger|scavenging]] on [[carrion]] is not uncommon (despite having once been thought to be very rare in all owls), including instances of [[reindeer]] (''Rangifer tarandus'') body parts brought to nests and owls following [[polar bear]]s to secondarily feed on their kills. Even huge [[marine mammal]]s such as [[walrus]] (''Odobenus rosmarus'') and whales can be fed upon by these owls when the opportunity occurs.<ref name= Holt/><ref>{{cite journal|doi=10.3356/0892-1016-53.4.410}}</ref> Snowy owls produce a [[Pellet (ornithology)|pellet]] that in different areas averages a median of about {{convert|80|x|30|mm|in|abbr=on}}, averaging up to {{convert|92|mm|in|abbr=on}} in length as in Europe.<ref name= Cramp/><ref name= Detienne/><ref name= Patterson/><ref name= Hagen/>
Snowy owls may not infrequently exploit prey inadvertently provided or compromised by human activities, including ducks injured by [[Hunting|duck hunters]], [[Red phalarope|birds]] maimed by [[Antenna (radio)|antenna]] wires, various animals caught in human [[Trapping|traps]] and [[trapline]]s as well as [[Domestication of animals|domestic]] or wild prey being bred or farmed by humans in enclosures.<ref name= Watson/><ref name=Wiggins/><ref>Brooks, W. S. (1915). ''Notes on birds from east Siberia and Arctic Alaska''. Bulletin of the Museum of Comparative Zoology 59:361–413.</ref><ref>Nagell, B. & Frycklund, I. (1965). ''The irruption of the Snowy Owl (Nyctea scandiaca) in Scandinavia in the winters of 1960–1963 and notes on its behavior''. Vår Fågelvärld 24 (1): 26–55.</ref><ref>King, B., Nayler, F. & Wardle, F. (1966). ''Feeding and resting behavior of a Snowy Owl in Scilly''. British Birds 59 (3): 108.</ref><ref name= Robertson>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/jrr/v037n02/p00164-p00166.pdf|author1=Robertson, G. J. |author2=Gilchrist, H. G. |year=2003|title=Wintering Snowy Owls feed on sea ducks in the Belcher Islands, Nunavut, Canada|journal= Journal of Raptor Research |volume=37 |issue=2|pages= 164–166}}</ref> A wide variety of accrued reports show that the snowy owl that [[Scavenger|scavenging]] on [[carrion]] is not uncommon (despite having once been thought to be very rare in all owls), including instances of [[reindeer]] (''Rangifer tarandus'') body parts brought to nests and owls following [[polar bear]]s to secondarily feed on their kills. Even huge [[marine mammal]]s such as [[walrus]] (''Odobenus rosmarus'') and whales can be fed upon by these owls when the opportunity occurs.<ref name= Holt/><ref>{{cite journal|doi=10.3356/0892-1016-53.4.410}}</ref> Snowy owls produce a [[Pellet (ornithology)|pellet]] that in different areas averages a median of about {{convert|80|x|30|mm|in|abbr=on}}, averaging up to {{convert|92|mm|in|abbr=on}} in length as in Europe.<ref name= Cramp/><ref name= Detienne/><ref name= Patterson/><ref name= Hagen/>
On the isle of [[St. Kilda, Scotland|St. Kilda]], 24 pellets were found for non-breeding snowy owls that stayed through the early summer. Of 46 prey items, the [[St Kilda field mouse]] (''Apodemus sylvaticus hirtensis'') was predominant by number at 69.6% but constituted 16.8% of biomass while adult [[Atlantic puffin]] (''Fratercula arctica'') constituted 63.5% of the prey biomass and 26% by number (rest of the balance being juvenile puffins and [[great skua]]s (''Stercorarius skua'')).<ref name= Miles>Miles, W. T. S., & Money, S. (2008). ''Behaviour and diet of non-breeding Snowy Owls on St Kilda''. Scottish Birds, 28, 11.</ref> The main subspecies of [[wood mouse]] was similarly dominant in the diet within [[County Mayo]], Ireland and were presumably snatched at night due to their strict [[nocturnality]].<ref>{{cite journal|author1=Murrey, T. |author2= Sleeman, D. |year=2005|title=Dietary analysis from the Snowy Owls pellets ''Nyctea scandiaca'' Linnaeus 1958, from the Mullet Peninsula, Co, Mayo|journal= Irish Naturalists' Journal|volume= 283|pages= 136}}</ref> In [[Knockando, Moray|Knockando]], the winter diet was led by [[European rabbit]]s (40.1%), [[red grouse]] (''Lagopus lagopus scotica'') (26.4%) and adult [[mountain hare]] (''Lepus timidus'') (20.9%) (in 156 pellets); in [[Ben Macdui]], the diet was led by rock ptarmigan (72.3%), [[field vole]]s (''Microtus agrestis'') and juvenile mountain hare (8.5%) (33 pellets); in [[Cabrach]], the diet was led by red grouse (40%), mountain hare (20%) and European rabbit (15%) (16 pellets).<ref name= Savory>{{cite journal|url=https://www.researchgate.net/publication/336837560_Unpublished_information_in_the_SOC_Archive_on_Snowy_Owl_diet_at_three_locations_in_Moray_in_the_1960s_Unpublished_information_in_the_SOC_Archive_on_Snowy_Owl_diet_at_three_locations_in_Moray_in_the_19|author=Savory, J. |year=2019|title=Unpublished information in the SOC Archive on Snowy Owl diet at three locations in Moray in the 1960s|journal= Scottish Birds|volume= 202|issue=204|pages= 202}}</ref> Among 110 prey items found for snowy owls found wintering during irruption in southern Finland, all but 1 prey item were field voles (the only other prey being a single [[long-tailed duck]] (''Clangula hyemalis'')).<ref name= Hakala/> Far to the east, wintering owls in the [[Irkutsky District]] were found to subsist mostly on [[narrow-headed vole]]s (''Microtus gregalis'').<ref name= Maleev>Maleev, V.G. & Popov, V. V. (2007). ''Birds of forest-steppes of the Upper Angara river basin''. Irkutsk.</ref> In a wintering population in Kurgaldga Nature Reserve of Kazakhstan, the main foods were [[grey red-backed vole]]s at 47.4%, [[winter white dwarf hamster]] (''Phodopus sungorus'') at 18.4%, [[steppe pika]] (''Ochotona pusilla'') at 7.9%, muskrat at 7.9%, [[Eurasian skylark]] (''Alauda arvensis'') at 7.9%, [[grey partridge]] at 5.3%, and both [[steppe polecat]] (''Mustela eversmanii'') and [[yellowhammer]] (''Emberiza citrinella'') at 2.6%<ref>Mosalev, A. (1969). ''About wintering of Snowy Owl in the Kurgaldga Nature Reserve''.</ref> On the [[Kuril Islands]], wintering snowy owls main foods were reported as tundra voles, brown rats, ermines and whimbrel, in roughly that order.<ref name= Potapov/>
On the isle of [[St. Kilda, Scotland|St. Kilda]], 24 pellets were found for non-breeding snowy owls that stayed through the early summer. Of 46 prey items, the [[St Kilda field mouse]] (''Apodemus sylvaticus hirtensis'') was predominant by number at 69.6% but constituted 16.8% of biomass while adult [[Atlantic puffin]] (''Fratercula arctica'') constituted 63.5% of the prey biomass and 26% by number (rest of the balance being juvenile puffins and [[great skua]]s (''Stercorarius skua'')).<ref name= Miles>Miles, W. T. S., & Money, S. (2008). ''Behaviour and diet of non-breeding Snowy Owls on St Kilda''. Scottish Birds, 28, 11.</ref> The main subspecies of [[wood mouse]] was similarly dominant in the diet within [[County Mayo]], Ireland and were presumably snatched at night due to their strict [[nocturnality]].<ref>{{cite journal|author1=Murrey, T. |author2= Sleeman, D. |year=2005|title=Dietary analysis from the Snowy Owls pellets ''Nyctea scandiaca'' Linnaeus 1958, from the Mullet Peninsula, Co, Mayo|journal= Irish Naturalists' Journal|volume= 283|pages= 136}}</ref> In [[Knockando, Moray|Knockando]], the winter diet was led by [[European rabbit]]s (40.1%), [[red grouse]] (''Lagopus lagopus scotica'') (26.4%) and adult [[mountain hare]] (''Lepus timidus'') (20.9%) (in 156 pellets); in [[Ben Macdui]], the diet was led by rock ptarmigan (72.3%), [[field vole]]s (''Microtus agrestis'') and juvenile mountain hare (8.5%) (33 pellets); in [[Cabrach]], the diet was led by red grouse (40%), mountain hare (20%) and European rabbit (15%) (16 pellets).<ref name= Savory>{{cite journal|url=https://www.researchgate.net/publication/336837560_Unpublished_information_in_the_SOC_Archive_on_Snowy_Owl_diet_at_three_locations_in_Moray_in_the_1960s_Unpublished_information_in_the_SOC_Archive_on_Snowy_Owl_diet_at_three_locations_in_Moray_in_the_19|author=Savory, J. |year=2019|title=Unpublished information in the SOC Archive on Snowy Owl diet at three locations in Moray in the 1960s|journal= Scottish Birds|volume= 202|issue=204|pages= 202}}</ref> Among 110 prey items found for snowy owls found wintering during irruption in southern Finland, all but 1 prey item were field voles (the only other prey being a single [[long-tailed duck]] (''Clangula hyemalis'')).<ref name= Hakala/> Far to the east, wintering owls in the [[Irkutsky District]] were found to subsist mostly on [[narrow-headed vole]]s (''Microtus gregalis'').<ref name= Maleev>Maleev, V.G. & Popov, V. V. (2007). ''Birds of forest-steppes of the Upper Angara river basin''. Irkutsk.</ref> In a wintering population in Kurgaldga Nature Reserve of Kazakhstan, the main foods were [[grey red-backed vole]]s at 47.4%, [[winter white dwarf hamster]] (''Phodopus sungorus'') at 18.4%, [[steppe pika]] (''Ochotona pusilla'') at 7.9%, muskrat at 7.9%, [[Eurasian skylark]] (''Alauda arvensis'') at 7.9%, [[grey partridge]] at 5.3%, and both [[steppe polecat]] (''Mustela eversmanii'') and [[yellowhammer]] (''Emberiza citrinella'') at 2.6%<ref>Mosalev, A. (1969). ''About wintering of Snowy Owl in the Kurgaldga Nature Reserve''.</ref> On the [[Kuril Islands]], wintering snowy owls main foods were reported as tundra voles, brown rats, ermines and whimbrel, in roughly that order.<ref name= Potapov/>


Data from the [[Logan Airport]] in over 6,000 pellets shows that meadow vole and brown rat predominated the diet in the area, supplanted by assorted birds both small and large.<ref name= Holt/><ref name= Smith/> [[American black duck]]s were primarily taken among bird species with other birds taken here including relatively large and diverse species [[Canada geese]] (''Branta canadensis''), brants, [[American herring gull]]s (''Larus argentatus''), [[double-crested cormorant]] (''Phalacrocorax auritus''), [[great blue heron]] (''Ardea herodias''), in addition to some formidable mammals such as [[Cat|house cat]], [[American mink]] (''Mustela vision''), and [[striped skunk]] (''Mephitis mephitis'').<ref name= Holt/><ref name= Smith/> Given the large size of some of this prey, it can be projected that the snowy owl can kill adult prey of around twice their own weight (i.e. geese, cats, skunks, etc.).<ref name= Holt/><ref name= Smith/> Other large prey is sometimes taken by snowy owls, all roughly within the {{convert|2|to|5|kg|lb|abbr=on}} weight range often include adults of large [[leporid]]s such as [[Arctic hare]] (''Lepus arcticus''),<ref name= Holt/> [[Alaskan hare]] (''Lepus othus''),<ref>Best, T. L., & Henry, T. H. (1994). ''Lepus othus''. Mammalian Species, (458), 1–5.</ref> [[mountain hare]]<ref>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V54/V54_N08/V54_N08_P307_320_A051.pdf|author=Bergman, G. |year=1961|title=The food of birds of prey and owls in Fenno-Scandia|journal= British Birds|volume= 54|issue=8|pages= 307–320}}</ref> and [[white-tailed jackrabbit]]s (''Lepus townsendii'').<ref name= Boxall2/> As well as several species of geese, probable cygnets of [[Tundra swan|Bewick's swan]]s (''Cygnus columbianus bewickii'')<ref>Nagy, S., Petkov, N., Rees, E., Solokha, A., Hilton, G., Beekman, J., & Nolet, B. (2012). [https://www.unep-aewa.org/en/publication/international-single-species-action-plan-conservation-northwest-european-population International single species action plan for the conservation of the northwest European population of Bewick's Swan (''Cygnus columbianus bewickii'')]. Wetlands International and The Wildfowl & Wetlands Trust (WWT), AEWA Technical Series, (44).</ref> as well as adults of the following: [[western capercaillie]] (''Tetrao urogallus'') (of both sexes),<ref>Gilyazov, A. V. (2005). ''Snowy Owl Nyctea scandiaca Linnaeus, 1758''. Red-data Book of the Murmansk Region. Murmansk: Murmansk book publishers: 316—318. [in Russian].</ref> [[greater sage-grouse]] (''Centrocercus urophasianus'')<ref>{{cite journal|doi=10.1002/jwmg.21168}}</ref> and [[yellow-billed loon]]s (''Gavia adamsii'').<ref>Uher-Koch, B. D., M. R. North, and J. A. Schmutz (2020). Yellow-billed Loon (''Gavia adamsii''), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.</ref> At the other end of the scale, the snowy owl has been known to take birds down to size of {{convert|19.5|g|oz|abbr=on}} [[dark-eyed junco]]s (''Junco hyemalis'') and mammals down the size of {{convert|8.1|g|oz|abbr=on}} [[common shrew]]s (''Sorex araneus'').<ref name= Hakala/><ref name= Young/><ref name= CRC1>Dunning, Jr., J. B. (1993). ''CRC handbook of avian body masses''. CRC Press, Boca Raton, FL.</ref> Fish are rarely taken anywhere but the snowy owl has been known to prey upon [[Arctic char]] (''Salvelinus alpinus'') and [[lake trout]] (''Salvelinus namaycush'').<ref name= Voous/><ref name= Gross/><ref name= Bailey>Bailey, A. M. (1948). ''Birds of Arctic Alaska''. Colorado Mus. Nat. Hist., Popular Ser., 8.</ref>
Data from the [[Logan Airport]] in over 6,000 pellets shows that meadow vole and brown rat predominated the diet in the area, supplanted by assorted birds both small and large.<ref name= Holt/> [[American black duck]]s were primarily taken among bird species with other birds taken here including relatively large and diverse species [[Canada geese]] (''Branta canadensis''), brants, [[American herring gull]]s (''Larus argentatus''), [[double-crested cormorant]] (''Phalacrocorax auritus''), [[great blue heron]] (''Ardea herodias''), in addition to some formidable mammals such as [[Cat|house cat]], [[American mink]] (''Mustela vision''), and [[striped skunk]] (''Mephitis mephitis'').<ref name= Holt/> Given the large size of some of this prey, it can be projected that the snowy owl can kill adult prey of around twice their own weight (i.e. geese, cats, skunks, etc.).<ref name= Holt/> Other large prey is sometimes taken by snowy owls, all roughly within the {{convert|2|to|5|kg|lb|abbr=on}} weight range often include adults of large [[leporid]]s such as [[Arctic hare]] (''Lepus arcticus''),<ref name= Holt/> [[Alaskan hare]] (''Lepus othus''),<ref>Best, T. L., & Henry, T. H. (1994). ''Lepus othus''. Mammalian Species, (458), 1–5.</ref> [[mountain hare]]<ref>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V54/V54_N08/V54_N08_P307_320_A051.pdf|author=Bergman, G. |year=1961|title=The food of birds of prey and owls in Fenno-Scandia|journal= British Birds|volume= 54|issue=8|pages= 307–320}}</ref> and [[white-tailed jackrabbit]]s (''Lepus townsendii'').<ref name= Boxall2/> As well as several species of geese, probable cygnets of [[Tundra swan|Bewick's swan]]s (''Cygnus columbianus bewickii'')<ref>Nagy, S., Petkov, N., Rees, E., Solokha, A., Hilton, G., Beekman, J., & Nolet, B. (2012). [https://www.unep-aewa.org/en/publication/international-single-species-action-plan-conservation-northwest-european-population International single species action plan for the conservation of the northwest European population of Bewick's Swan (''Cygnus columbianus bewickii'')]. Wetlands International and The Wildfowl & Wetlands Trust (WWT), AEWA Technical Series, (44).</ref> as well as adults of the following: [[western capercaillie]] (''Tetrao urogallus'') (of both sexes),<ref>Gilyazov, A. V. (2005). ''Snowy Owl Nyctea scandiaca Linnaeus, 1758''. Red-data Book of the Murmansk Region. Murmansk: Murmansk book publishers: 316—318. [in Russian].</ref> [[greater sage-grouse]] (''Centrocercus urophasianus'')<ref>{{cite journal|doi=10.1002/jwmg.21168}}</ref> and [[yellow-billed loon]]s (''Gavia adamsii'').<ref>Uher-Koch, B. D., M. R. North, and J. A. Schmutz (2020). Yellow-billed Loon (''Gavia adamsii''), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.</ref> At the other end of the scale, the snowy owl has been known to take birds down to size of {{convert|19.5|g|oz|abbr=on}} [[dark-eyed junco]]s (''Junco hyemalis'') and mammals down the size of {{convert|8.1|g|oz|abbr=on}} [[common shrew]]s (''Sorex araneus'').<ref name= Hakala/><ref name= Young/><ref name= CRC1>Dunning, Jr., J. B. (1993). ''CRC handbook of avian body masses''. CRC Press, Boca Raton, FL.</ref> Fish are rarely taken anywhere but the snowy owl has been known to prey upon [[Arctic char]] (''Salvelinus alpinus'') and [[lake trout]] (''Salvelinus namaycush'').<ref name= Voous/><ref name= Gross/><ref name= Bailey>Bailey, A. M. (1948). ''Birds of Arctic Alaska''. Colorado Mus. Nat. Hist., Popular Ser., 8.</ref>


===Interspecific predatory relationships===
===Interspecific predatory relationships===
The snowy owl is in many ways a very unique owl and differs from other species of owl in its [[ecological niche]].<ref name= Voous/><ref name= Johnsgard/> Only one other owl, the [[short-eared owl]], is known to breed in the High Arctic.<ref name= Voous/> However, the snowy owl shares its primary prey, the [[True lemming|brown]] and [[collared lemming]]s, with a number of other avian predators. In sometimes differing parts of the Arctic, competing predators for lemmings are, in addition to short-eared owls, [[pomarine jaeger]]s (''Stercorarius pomarinus''), [[long-tailed jaeger]]s (''Stercorarius longicaudus''), [[rough-legged buzzard]]s (''Buteo lagopus''), [[hen harrier]]s (''Circus cyaenus''), [[northern harrier]]s (''Circus hudsonius'') and generally less specialized [[gyrfalcon]]s (''Falco rusticollis''), [[peregrine falcon]]s (''Falco peregrinus''), [[glaucous gull]]s (''Larus hypoboreus'') and [[common raven]]s (''Corvus corax''). Certain carnivorous mammals, especially the [[Arctic fox]] and, in this region, the [[Stoat|ermine]], are also specialized to hunt lemmings.<ref name= Voous/><ref name= Pitelka/><ref>{{cite journal|doi=10.2307/3545963}}</ref><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v082n02/p0130-p0157.pdf|author=Maher, W. J. |year=1970|title=The Pomarine Jaeger as a Brown Lemming predator in northern Alaska|journal= Wilson Bulletin|volume= 82|pages= 130–157}}</ref> Most of the lemming predators are intolerant of the competition given the scattered nature of lemming populations and will displace and/or kill one another given the chance. However, given the need to conserve energy in the extreme environment, the predators may react passively to one another.<ref>{{cite journal|jstor=4314894|author=Wiklund, C. G., Angerbjörn, A., Isakson, E., Kjellén, N., & Tannerfeldt, M. |year=1999|title=Lemming predators on the Siberian tundra|journal=Ambio|volume= 281–286}}</ref><ref name="Gilg" /> When unusually breeding south in the Subarctic such as western Alaska, Scandinavia and central Russia, the number of predators with which the snowy owls are obligated to share prey and compete with may be too numerous to name.<ref name= Potapov/> The taking of the young and eggs of snowy owls has been committed by a large number of predators: [[Buteo|hawks]] and [[eagle]]s, the northern [[Skua|jaeger]]s, peregrine and gyrfalcons, glaucous gulls, common ravens, [[Arctic wolf|Arctic wolves]] (''Canis lupus arctos''), [[polar bear]]s, [[brown bear]]s (''Ursus arctos''), [[wolverine]]s (''Gulo gulo'') and perhaps especially the Arctic fox.<ref name= Holt/><ref name= Taylor/><ref>Ovsyanikov, N.G. & Menushina, I.E. (1986). ''[Competition for food between the Snowy Owl (Nyctea scandiaca) and the arctic fox (Alopex lagopus)]''. Zoologischeskii Zhurnal. 65(6): 901–910. In Russian with English summary.</ref> Adult snowy owls on the breeding grounds are far less vulnerable and can be justifiably qualified as an [[apex predator]].<ref name= Konig/><ref name= Voous/> Instances of killing of adult snowy owls on the breeding grounds have been witnessed to be committed by a pair of [[pomarine jaeger]]s on an incubating adult female snowy owl (possibly merely a competitive attack as she was left uneaten) and by an Arctic fox that killed an adult male snowy owl.<ref name= Bailey/><ref>Menyushina, I. E. (1994). "Interspecies relation of the polar fox (''Alopex lagopus'' L.) and the Snowy Owl (''Nyctea scandiaca'' L.) during the breeding season in the Wrangel Island. 1". Lutreola 3: 15–21.</ref>
The snowy owl is in many ways a very unique owl and differs from other species of owl in its [[ecological niche]].<ref name= Voous/><ref name= Johnsgard/> Only one other owl, the [[short-eared owl]], is known to breed in the High Arctic.<ref name= Voous/> However, the snowy owl shares its primary prey, the [[True lemming|brown]] and [[collared lemming]]s, with a number of other avian predators. In sometimes differing parts of the Arctic, competing predators for lemmings are, in addition to short-eared owls, [[pomarine jaeger]]s (''Stercorarius pomarinus''), [[long-tailed jaeger]]s (''Stercorarius longicaudus''), [[rough-legged buzzard]]s (''Buteo lagopus''), [[hen harrier]]s (''Circus cyaenus''), [[northern harrier]]s (''Circus hudsonius'') and generally less specialized [[gyrfalcon]]s (''Falco rusticollis''), [[peregrine falcon]]s (''Falco peregrinus''), [[glaucous gull]]s (''Larus hypoboreus'') and [[common raven]]s (''Corvus corax''). Certain carnivorous mammals, especially the [[Arctic fox]] and, in this region, the [[Stoat|ermine]], are also specialized to hunt lemmings.<ref name= Voous/><ref name= Pitelka/><ref>{{cite journal|doi=10.2307/3545963}}</ref><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v082n02/p0130-p0157.pdf|author=Maher, W. J. |year=1970|title=The Pomarine Jaeger as a Brown Lemming predator in northern Alaska|journal= Wilson Bulletin|volume= 82|pages= 130–157}}</ref> Most of the lemming predators are intolerant of the competition given the scattered nature of lemming populations and will displace and/or kill one another given the chance. However, given the need to conserve energy in the extreme environment, the predators may react passively to one another.<ref>{{cite journal|jstor=4314894|author=Wiklund, C. G., Angerbjörn, A., Isakson, E., Kjellén, N., & Tannerfeldt, M. |year=1999|title=Lemming predators on the Siberian tundra|journal=Ambio|volume= 281–286}}</ref><ref name="Gilg" /> When unusually breeding south in the Subarctic such as western Alaska, Scandinavia and central Russia, the number of predators with which the snowy owls are obligated to share prey and compete with may be too numerous to name.<ref name= Potapov/> The taking of the young and eggs of snowy owls has been committed by a large number of predators: [[Buteo|hawks]] and [[eagle]]s, the northern [[Skua|jaeger]]s, peregrine and gyrfalcons, glaucous gulls, common ravens, [[Arctic wolf|Arctic wolves]] (''Canis lupus arctos''), [[polar bear]]s, [[brown bear]]s (''Ursus arctos''), [[wolverine]]s (''Gulo gulo'') and perhaps especially the Arctic fox.<ref name= Holt/><ref name= Taylor/><ref>Ovsyanikov, N.G. & Menushina, I.E. (1986). ''[Competition for food between the Snowy Owl (Nyctea scandiaca) and the arctic fox (Alopex lagopus)]''. Zoologischeskii Zhurnal. 65(6): 901–910. In Russian with English summary.</ref> Adult snowy owls on the breeding grounds are far less vulnerable and can be justifiably qualified as an [[apex predator]].<ref name= Konig/><ref name= Voous/> Instances of killing of adult snowy owls on the breeding grounds have been witnessed to be committed by a pair of [[pomarine jaeger]]s on an incubating adult female snowy owl (possibly merely a competitive attack as she was left uneaten) and by an Arctic fox that killed an adult male snowy owl.<ref name= Bailey/><ref>Menyushina, I. E. (1994). "Interspecies relation of the polar fox (''Alopex lagopus'' L.) and the Snowy Owl (''Nyctea scandiaca'' L.) during the breeding season in the Wrangel Island. 1". Lutreola 3: 15–21.</ref>
[[File:Die Raubvögel Deutschlands und des angrenzenden Mitteleuropas (Pl. L) (21138120888).jpg|thumb|An early illustration showing snowy owl predation upon a [[gyrfalcon]].]]
[[File:Die Raubvögel Deutschlands und des angrenzenden Mitteleuropas (Pl. L) (21138120888).jpg|thumb|An early illustration showing snowy owl predation upon a [[gyrfalcon]].]]
When it goes south to winter outside of the Arctic, the snowy owl has a potential to interact with a number of additional predators.<ref name= Voous/> By necessity, it shares its wintertime diverse prey with a number of formidable predators.<ref name= Voous/><ref name= Holt/> These are known to include their cousins, the [[great horned owl]] and the [[Eurasian eagle-owl]]. They are relieved of heavy competition from the related species by differing temporal activity, i.e. being more likely to actively hunt in daytime, and by habitat, using rather more open (quite often nearly treeless) habitats than them.<ref name= Potapov/><ref name= Voous/> During a study of wintering snowy owls in [[Saskatchewan]], the authors indicated that the snowy owls may avoid areas inhabited and defended by great horned owls. Although they usually occurred here outside of a {{convert|800|m|ft|abbr=on}} radius of central great horned owl ranges, they did not avoid the {{convert|1600|m|ft|abbr=on}} radius and different habitat usage may be a dictating factor.<ref name= Chang2>Chang, A. M. (2017). ''Habitat use, movement patterns, and body condition of male and female Snowy Owls (Bubo scandiacus) in winter'' (Doctoral dissertation, University of Saskatchewan).</ref> Given their mildly slighter size, it is unlikely that great horned owls (unlike the larger eagle-owl) would regularly dominate snowy owls in interactions and either species may give way to other depending on the size and disposition of the owls involved.<ref name= Potapov/><ref name= Voous/> Little study has been undertaken into the [[Trophic level|trophic competition]] of snowy owls with other predators during winter and, due to their scarcity, few predators are likely to expel much energy on competitive interactions with them, although many other predators will engage in anti-predator [[Mobbing (animal behavior)|mobbing]] of snowy owls.<ref name= Voous/><ref name= Holt/> Largely in winter, snowy owls have been the victim of a number of larger avian predators, though attacks are likely to be singular and rare.<ref name= Voous/><ref name= Holt/> Instances of predation on snowy owls are known to have been committed several times in winter only by [[Eurasian eagle-owl]]s.<ref name= Mikkola3>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V69/V69_N04/V69_N04_P144_154_A030.pdf|author=Mikkola, H. |year=1976|title=Owls killing and killed by other owls and raptors in Europe|journal= British Birds|volume= 69|pages= 144–154}}</ref> Additionally, [[golden eagle]]s (''Aquila chrysaetos'') have been known to prey on snowy owls as well as all northern [[sea eagle]]s: the [[Bald eagle|bald]] (''Haliaeetus leucocephalus''), [[White-tailed eagle|white-tailed]] (''Haliaeetus albicilla'') and [[Steller's sea eagle]]s (''Haliaeetus pelagicus'').<ref name= Holt/><ref name= Campbell/><ref>{{cite journal|author=Johnson, M.J. |year=1995|title=Bald Eagle predation on Snowy Owl|journal= Loon|volume= 67|issue=2|pages=107}}</ref> Snowy owls are also sometimes killed by birds that are mobbing them. In one instance, a [[peregrine falcon]] killed a snowy owl in a stoop after the owl had itself killed a fledgling falcon.<ref name= Bent/><ref name= Bailey/><ref>Nelson, E. W. (1887). ''Birds of Alaska'', p. 35-222. In H. W. Henshaw [ed.], Report upon natural history collections made in Alaska between the years 1877 and 188 1. No. III Arctic Series, Signal Service, U.S. Army, Government Printing Office,-Washington, DC.</ref> Anecdotal report indicate predation by [[gyrfalcon]]s (on snowy owls of unknown age and condition) but it was possibly also an act of mobbing.<ref name= Heggoy>Heggøy, O., & Øien, I. J. (2014). ''Conservation status of birds of prey and owls in Norway''. NOF/BirdLife Norway-Report, 1, 1–129.</ref> In another, a huge [[Flock (birds)|throng]] of [[Arctic tern]]s (''Sterna paradisaea'') relentlessly swarmed and attacked a snowy owl until it meet its demise.<ref>Meinertzhagen, R. (1959). ''Pirates and Predators: The piratical and predatory habits of birds''. Oliver & Boyd.</ref>
When it goes south to winter outside of the Arctic, the snowy owl has a potential to interact with a number of additional predators.<ref name= Voous/> By necessity, it shares its wintertime diverse prey with a number of formidable predators.<ref name= Voous/><ref name= Holt/> These are known to include their cousins, the [[great horned owl]] and the [[Eurasian eagle-owl]]. They are relieved of heavy competition from the related species by differing temporal activity, i.e. being more likely to actively hunt in daytime, and by habitat, using rather more open (quite often nearly treeless) habitats than them.<ref name= Potapov/><ref name= Voous/> During a study of wintering snowy owls in [[Saskatchewan]], the authors indicated that the snowy owls may avoid areas inhabited and defended by great horned owls. Although they usually occurred here outside of a {{convert|800|m|ft|abbr=on}} radius of central great horned owl ranges, they did not avoid the {{convert|1600|m|ft|abbr=on}} radius and different habitat usage may be a dictating factor.<ref name= Chang2>Chang, A. M. (2017). ''Habitat use, movement patterns, and body condition of male and female Snowy Owls (Bubo scandiacus) in winter'' (Doctoral dissertation, University of Saskatchewan).</ref> Given their mildly slighter size, it is unlikely that great horned owls (unlike the larger eagle-owl) would regularly dominate snowy owls in interactions and either species may give way to other depending on the size and disposition of the owls involved.<ref name= Potapov/><ref name= Voous/> Little study has been undertaken into the [[Trophic level|trophic competition]] of snowy owls with other predators during winter and, due to their scarcity, few predators are likely to expel much energy on competitive interactions with them, although many other predators will engage in anti-predator [[Mobbing (animal behavior)|mobbing]] of snowy owls.<ref name= Voous/><ref name= Holt/> Largely in winter, snowy owls have been the victim of a number of larger avian predators, though attacks are likely to be singular and rare.<ref name= Voous/><ref name= Holt/> Instances of predation on snowy owls are known to have been committed several times in winter only by [[Eurasian eagle-owl]]s.<ref name= Mikkola3>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V69/V69_N04/V69_N04_P144_154_A030.pdf|author=Mikkola, H. |year=1976|title=Owls killing and killed by other owls and raptors in Europe|journal= British Birds|volume= 69|pages= 144–154}}</ref> Additionally, [[golden eagle]]s (''Aquila chrysaetos'') have been known to prey on snowy owls as well as all northern [[sea eagle]]s: the [[Bald eagle|bald]] (''Haliaeetus leucocephalus''), [[White-tailed eagle|white-tailed]] (''Haliaeetus albicilla'') and [[Steller's sea eagle]]s (''Haliaeetus pelagicus'').<ref name= Holt/><ref name= Campbell/><ref>{{cite journal|author=Johnson, M.J. |year=1995|title=Bald Eagle predation on Snowy Owl|journal= Loon|volume= 67|issue=2|pages=107}}</ref> Snowy owls are also sometimes killed by birds that are mobbing them. In one instance, a [[peregrine falcon]] killed a snowy owl in a stoop after the owl had itself killed a fledgling falcon.<ref name= Bent/><ref name= Bailey/><ref>Nelson, E. W. (1887). ''Birds of Alaska'', p. 35-222. In H. W. Henshaw [ed.], Report upon natural history collections made in Alaska between the years 1877 and 188 1. No. III Arctic Series, Signal Service, U.S. Army, Government Printing Office,-Washington, DC.</ref> Anecdotal report indicate predation by [[gyrfalcon]]s (on snowy owls of unknown age and condition) but it was possibly also an act of mobbing.<ref name= Heggoy>Heggøy, O., & Øien, I. J. (2014). [https://www.birdlife.no/innhold/bilder/2014/01/29/2586/nof_rapport_12014.pdf ''Conservation status of birds of prey and owls in Norway'']. NOF/BirdLife Norway-Report, 1, 1–129.</ref> In another, a huge [[Flock (birds)|throng]] of [[Arctic tern]]s (''Sterna paradisaea'') relentlessly swarmed and attacked a snowy owl until it meet its demise.<ref>Meinertzhagen, R. (1959). ''Pirates and Predators: The piratical and predatory habits of birds''. Oliver & Boyd.</ref>


Almost certainly more often than being victim of other predators, snowy owls are known to dominate, kill and feed on a large diversity of other predators.<ref name= Voous/><ref name= Mikkola3/> Snowy owls, much like other ''Bubo'' owls, will opportunistically kill other birds of prey and predators. Although they will readily plunder the nests of other raptorial birds given the opportunity, most predations are on full-grown raptorial birds during winter due to the scarcity of raptor nests in the open tundra.<ref name= Voous/> In addition, most competing predators of the Arctic, excepting the very large mammals, are probably vulnerable to a hungry snowy owl.<ref name= Voous/><ref name= Holt/> In data from the [[Logan Airport]] alone over different winters, the snowy owls were observed to have preyed upon an impressive diversity of other raptorial birds: [[rough-legged buzzard]]s, [[American kestrel]]s (''Falco sparverius''), [[peregrine falcon]]s, [[barn owl]]s, other snowy owls, [[barred owl]]s (''Strix varia''), [[northern saw-whet owl]]s (''Aegolius acadicus'') and [[short-eared owl]]s. While owls are likely encountered during corresponding hunting times, it is likely that the swift falcons are usually ambushed at night (much as other ''Bubo'' owls will do).<ref name= Holt/><ref name= Smith/> In both the tundra and the wintering ground, there are several accounts of predation by snowy owls on short-eared owls.<ref name= Potapov/><ref name= Mikkola3/><ref>{{cite journal|doi=10.2307/1368028}}</ref> In addition, snowy owls have been known to prey on [[northern harrier]]s,<ref name= Holt/><ref name= Smith/> [[northern goshawk]]s (''Accipiter gentilis'')<ref name= Voous/> and [[gyrfalcon]]s.<ref name= Voous/><ref name= Mikkola3/> In a few cases, both juvenile and adult [[Arctic fox]]es have been known to fall prey to snowy owls.<ref name= Parker/><ref name= Stenkewitz/><ref name= Krechmar/><ref name="Gilg">{{cite journal|doi=10.1111/j.2006.0030-1299.14125.x}}</ref><ref>{{cite journal|title=''Alopex lagopus''|doi=10.1644/0.713.1}}</ref> A wintering snowy owl in [[Saskatchewan]] was observed to have preyed on an adult [[red fox]] (''Vulpes vulpes''). Predation by snowy owls on red foxes was also reported in the [[Irkutsky District]] of Russia. With an adult weight around {{convert|6|kg|lb|abbr=on}} (and far from defenseless), red fox may be the largest known prey known for snowy owls.<ref name= Maleev/><ref>{{cite journal|doi=10.29173/bluejay3979}}</ref> Besides aforementioned predation on domestic cats and skunks, several members of the [[weasel]] family, both small and relatively large, are known to be opportunistically hunted by snowy owls.<ref name= Potapov/><ref name= Voous/><ref name= Holt/><ref name= Smith/><ref name= Hakala/><ref>{{cite journal|doi=10.2307/3565424}}</ref> As a result of its potential predator status, the snowy owl is frequently mobbed at all times of the year by other predatory birds, including fierce dive-bombing by several of the northern falcons on the wintering grounds, including even by the relatively tiny but fierce and very agile [[Merlin (bird)|merlin]] (''Falco columbarius''). The much bulkier snowy owls cannot match the speed and flight ability of a falcon, ai may be almost relentlessly tormented by some birds such as peregrines.<ref name= Voous/><ref name= Mikkola3/><ref>{{cite journal|doi=10.29173/bluejay208}}</ref>
Almost certainly more often than being victim of other predators, snowy owls are known to dominate, kill and feed on a large diversity of other predators.<ref name= Voous/><ref name= Mikkola3/> Snowy owls, much like other ''Bubo'' owls, will opportunistically kill other birds of prey and predators. Although they will readily plunder the nests of other raptorial birds given the opportunity, most predations are on full-grown raptorial birds during winter due to the scarcity of raptor nests in the open tundra.<ref name= Voous/> In addition, most competing predators of the Arctic, excepting the very large mammals, are probably vulnerable to a hungry snowy owl.<ref name= Voous/><ref name= Holt/> In data from the [[Logan Airport]] alone over different winters, the snowy owls were observed to have preyed upon an impressive diversity of other raptorial birds: [[rough-legged buzzard]]s, [[American kestrel]]s (''Falco sparverius''), [[peregrine falcon]]s, [[barn owl]]s, other snowy owls, [[barred owl]]s (''Strix varia''), [[northern saw-whet owl]]s (''Aegolius acadicus'') and [[short-eared owl]]s. While owls are likely encountered during corresponding hunting times, it is likely that the swift falcons are usually ambushed at night (much as other ''Bubo'' owls will do).<ref name= Holt/> In both the tundra and the wintering ground, there are several accounts of predation by snowy owls on short-eared owls.<ref name= Potapov/><ref name= Mikkola3/><ref>{{cite journal|doi=10.2307/1368028}}</ref> In addition, snowy owls have been known to prey on [[northern harrier]]s,<ref name= Holt/> [[northern goshawk]]s (''Accipiter gentilis'')<ref name= Voous/> and [[gyrfalcon]]s.<ref name= Voous/><ref name= Mikkola3/> In a few cases, both juvenile and adult [[Arctic fox]]es have been known to fall prey to snowy owls.<ref name= Parker/><ref name= Stenkewitz/><ref name= Krechmar/><ref name="Gilg">{{cite journal|doi=10.1111/j.2006.0030-1299.14125.x}}</ref><ref>{{cite journal|title=''Alopex lagopus''|doi=10.1644/0.713.1}}</ref> A wintering snowy owl in [[Saskatchewan]] was observed to have preyed on an adult [[red fox]] (''Vulpes vulpes''). Predation by snowy owls on red foxes was also reported in the [[Irkutsky District]] of Russia. With an adult weight around {{convert|6|kg|lb|abbr=on}} (and far from defenseless), red fox may be the largest known prey known for snowy owls.<ref name= Maleev/><ref>{{cite journal|doi=10.29173/bluejay3979}}</ref> Besides aforementioned predation on domestic cats and skunks, several members of the [[weasel]] family, both small and relatively large, are known to be opportunistically hunted by snowy owls.<ref name= Potapov/><ref name= Voous/><ref name= Holt/><ref name= Hakala/><ref>{{cite journal|doi=10.2307/3565424}}</ref> As a result of its potential predator status, the snowy owl is frequently mobbed at all times of the year by other predatory birds, including fierce dive-bombing by several of the northern falcons on the wintering grounds, including even by the relatively tiny but fierce and very agile [[Merlin (bird)|merlin]] (''Falco columbarius''). The much bulkier snowy owls cannot match the speed and flight ability of a falcon, ai may be almost relentlessly tormented by some birds such as peregrines.<ref name= Voous/><ref name= Mikkola3/><ref>{{cite journal|doi=10.29173/bluejay208}}</ref>


==Breeding==
==Breeding==


===Pair bond and breeding territory===
===Pair bond and breeding territory===
In Utqiaġvik, of 239 recorded breeding attempts, 232 were monogamous, the other 7 [[Bigamy|social bigamy]].<ref name= Holt/> On [[Baffin Island]], 1 male bred with 2 females and sired 11 total fledged young.<ref name= Watson/> Another case of bigamy was reported in Norway where the 2 females bred to one male were {{convert|1.3|km|mi|abbr=on}} apart in nest site location.<ref name= Hagen/> On Feltar from 1967 to 1975, a male breed with two females, 1 younger and was possibly his own [[Incest|daughter]]. In the Feltar males first time breeding with both females, he did not bring food to the younger female. However, when older female disappeared the following year, the male and younger female producing 4 young, but disappeared the subsequent year altogether in 1975.<ref name= Robinson/> There are also unconfirmed cases of [[polyandry]], with 1 female being fed by 2 males. Snowy owls can breed once per year but when food is scarce many do not even attempt to breed.<ref name= Konig/><ref name= Voous/> Despite frequent wandering in search of food, they generally adhere more so than to a strict breeding season than [[short-eared owl]]s nesting in the tundra.<ref name= Voous/> 9 radio-tagged female snowy owls about [[Bylot Island]] were tracked to study how pre-laying snow cover effects their searching behavior for breeding area. These tracked females searched an average of 36 days and covered an average of {{convert|1251|km|mi|abbr=on}}. It is thought that the male and female mutually find an attractive breeding spot independently and converge.<ref>{{cite journal|doi=10.1186/s40462-015-0028-7}}</ref> The breeding territory normally averages about {{convert|2.6|km2|sqmi|abbr=on}} as in both [[Baffin Island]] and [[Ellesmere Island]] but varies in accordance to abundance of food and density of owls.<ref name= Konig/><ref name= Watson/><ref name= MacDonald/> Nesting territories average at Baffin island in the range of {{convert|8|to|10|km2|sqmi|abbr=on}} during poor lemming years.<ref name= Watson/> Nesting territories may up to {{convert|22|km2|sqmi|abbr=on}} on [[Southampton Island]] and had a mean distance of {{convert|4.5|km|mi|abbr=on}} between active nests.<ref name= Sutton1/> In Utqiaġvik, nesting pairs can vary from none to at least 7 and the territories average {{convert|5|to|10|km2|sqmi|abbr=on}}, with mean nest distances of {{convert|1.5|to|6|km|mi|abbr=on}}.<ref name= Pitelka/> In the Norwegian highlands, nesting occurs only at times of plenty distances of {{convert|1.2|to|3.7|km|mi|abbr=on}} between nests, averaging {{convert|2.1|km|mi|abbr=on}}.<ref name= Hagen/> Males marks territory with singing and display flights and likely always initiates.<ref name= Watson/> During the display, he engages in exaggerated wing beats with a shallow undulating and bouncy courtship flight with wings held in a [[Dihedral (aeronautics)|dihedral]]. He often drops to the ground but then flies again to only glide gently back down. Overall, the flight is somewhat reminiscent of the flight of a [[moth]].<ref name= Watson/><ref name= Pitelka/><ref name= Tulloch/><ref name= Robinson/> Females will answer her mate with her song during courtship.<ref name= Konig/> While courting, the male often also carries a lemming in his bill, then bows with cocked tail, similarly as in related owls (seldom displaying some other prey like [[snow bunting]]s). He then flaps his wings open in an emphatic manner, with the ground display being relatively brief (about 5 minutes). The female may possibly refuse to breed if ritual not performed.<ref name= Watson/><ref name= Taylor/> A possible courtship was engaged in by a male in southern Saskatchewan when a female was sighted.<ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v094n01/p0079-p0081.pdf|author1=Boxall, P. C. |author2= Lein, M. R. |year=1982|title=Possible courtship behavior of Snowy Owls in winter|journal= Wilson Bulletin|volume= 94|pages=79–81}}</ref> On Southampton Island, at least 20 males observed in late May in a "lemming year".<ref name= Voous/><ref name= Sutton1/> Nesting territory defense displays, not highly different from courtship displays, includes undulating flight and stiffly raised wings with bouts of exaggerated, delayed wing beats, looking like enormous white moths exposing their white wings under the sun.<ref name= Taylor/> At times, competing males will interlock claws in mid-air.<ref name= Voous/> Territorial and nuptial displays are followed by a ground display by the male with the wings arched up in an "angel" posture, visible for well over a mile.<ref name= Voous/>
In Utqiaġvik, of 239 recorded breeding attempts, 232 were monogamous, the other 7 [[Bigamy|social bigamy]].<ref name= Holt/> On [[Baffin Island]], 1 male bred with 2 females and sired 11 total fledged young.<ref name= Watson/> Another case of bigamy was reported in Norway where the 2 females bred to one male were {{convert|1.3|km|mi|abbr=on}} apart in nest site location.<ref name= Hagen/> On Feltar from 1967 to 1975, a male breed with two females, 1 younger and was possibly his own [[Incest|daughter]]. In the Feltar males first time breeding with both females, he did not bring food to the younger female. However, when older female disappeared the following year, the male and younger female producing 4 young, but disappeared the subsequent year altogether in 1975.<ref name= Robinson/> There are also unconfirmed cases of [[polyandry]], with 1 female being fed by 2 males. Snowy owls can breed once per year but when food is scarce many do not even attempt to breed.<ref name= Konig/><ref name= Voous/> Despite frequent wandering in search of food, they generally adhere more so than to a strict breeding season than [[short-eared owl]]s nesting in the tundra.<ref name= Voous/> 9 radio-tagged female snowy owls about [[Bylot Island]] were tracked to study how pre-laying snow cover effects their searching behavior for breeding area. These tracked females searched an average of 36 days and covered an average of {{convert|1251|km|mi|abbr=on}}. It is thought that the male and female mutually find an attractive breeding spot independently and converge.<ref>{{cite journal|doi=10.1186/s40462-015-0028-7}}</ref> The breeding territory normally averages about {{convert|2.6|km2|sqmi|abbr=on}} as in both [[Baffin Island]] and [[Ellesmere Island]] but varies in accordance to abundance of food and density of owls.<ref name= Konig/><ref name= Watson/> Nesting territories average at Baffin island in the range of {{convert|8|to|10|km2|sqmi|abbr=on}} during poor lemming years.<ref name= Watson/> Nesting territories may up to {{convert|22|km2|sqmi|abbr=on}} on [[Southampton Island]] and had a mean distance of {{convert|4.5|km|mi|abbr=on}} between active nests.<ref name= Sutton1/> In Utqiaġvik, nesting pairs can vary from none to at least 7 and the territories average {{convert|5|to|10|km2|sqmi|abbr=on}}, with mean nest distances of {{convert|1.5|to|6|km|mi|abbr=on}}.<ref name= Pitelka/> In the Norwegian highlands, nesting occurs only at times of plenty distances of {{convert|1.2|to|3.7|km|mi|abbr=on}} between nests, averaging {{convert|2.1|km|mi|abbr=on}}.<ref name= Hagen/> Males marks territory with singing and display flights and likely always initiates.<ref name= Watson/> During the display, he engages in exaggerated wing beats with a shallow undulating and bouncy courtship flight with wings held in a [[Dihedral (aeronautics)|dihedral]]. He often drops to the ground but then flies again to only glide gently back down. Overall, the flight is somewhat reminiscent of the flight of a [[moth]].<ref name= Watson/><ref name= Pitelka/><ref name= Tulloch/><ref name= Robinson/> Females will answer her mate with her song during courtship.<ref name= Konig/> While courting, the male often also carries a lemming in his bill, then bows with cocked tail, similarly as in related owls (seldom displaying some other prey like [[snow bunting]]s). He then flaps his wings open in an emphatic manner, with the ground display being relatively brief (about 5 minutes). The female may possibly refuse to breed if ritual not performed.<ref name= Watson/><ref name= Taylor/> A possible courtship was engaged in by a male in southern Saskatchewan when a female was sighted.<ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v094n01/p0079-p0081.pdf|author1=Boxall, P. C. |author2= Lein, M. R. |year=1982|title=Possible courtship behavior of Snowy Owls in winter|journal= Wilson Bulletin|volume= 94|pages=79–81}}</ref> On Southampton Island, at least 20 males observed in late May in a "lemming year".<ref name= Voous/><ref name= Sutton1/> Nesting territory defense displays, not highly different from courtship displays, includes undulating flight and stiffly raised wings with bouts of exaggerated, delayed wing beats, looking like enormous white moths exposing their white wings under the sun.<ref name= Taylor/> At times, competing males will interlock claws in mid-air.<ref name= Voous/> Territorial and nuptial displays are followed by a ground display by the male with the wings arched up in an "angel" posture, visible for well over a mile.<ref name= Voous/>


===Nest sites===
===Nest sites===
[[File:Tundra Polygons and Pingos (9514080830).jpg|thumb|left|Snowy owls often seek out polygons such as these in the [[tundra]].]]
[[File:Tundra Polygons and Pingos (9514080830).jpg|thumb|left|Snowy owls often seek out polygons such as these in the [[tundra]].]]
Most individuals arrive at the nest site by April or May with a few overwintering arctic exceptions.<ref name= Murie/><ref name= Marine/><ref name= Pitelka2/><ref name= Fuller/> Males advertises potential nest sites to his mate by scratching the ground and spreading his wings over it.<ref name= Konig/> The nest is usually a shallow depression on a windswept eminence in the open tundra. There seems to be a variety of qualifiers for appropriate nest sites. The nest site is typically snow-free and dry relative to the surrounding environment, usually with a good view of the surrounding landscape. The nest may be made of [[ridge]]s, [[Mound|elevated mound]]s, high [[polygon]]s, [[hummock]]s, hills, man-made mounds and occasionally [[Outcrop|rocky outcrops]]. If covered with vegetation, taller plants that may obstruct view are plucked away sometimes.<ref name= Konig/><ref name= Voous/><ref name= Watson/><ref name= Pitelka2/><ref name= Holt3>{{cite journal|doi=10.5253/078.097.0422}}</ref> The nest sites are often long-established and naturally created by the freeze-thaw process of the tundra.<ref name= Voous/><ref name= Holt/> [[Bar (river morphology)|Gravel bars]] may be used as well.<ref name= Potapov/> The female may take the most active role in the nest's condition of any owl species.<ref name= Holt/><ref name= Mikkola/> No owl build their own nests but female snowy owls take about three days constructing a scrape, digging with her claws and rotating until a fairly circular bowl is formed. She will still not construct or add foreign materials to the nest (despite some circumstantial evidence of moss and grass from outside the nest mound being found).<ref name= Holt/><ref name= Murie/><ref name= Tulloch/> In two separate cases in Utqiaġvik, two separate females dug out a second scrape to the side and below the main nests and appeared to have called all chicks to the more secluded nest to ride out severe weather until the skies cleared.<ref name= Holt/> The Utqiaġvik nest scrapes averaged {{convert|47.7|x|44|cm|in|abbr=on}} in 91 with a mean depth of {{convert|9.8|cm|in|abbr=on}} while the scrapes were smaller in [[Hooper Bay]], reportedly {{convert|25|to|33|cm|in|abbr=on}} diameter and {{convert|4|to|9|cm|in|abbr=on}} in depth.<ref name= Murie/><ref name= Holt3/> Occasionally, in the lower tundra, snowy owls may too use old nests of [[rough-legged buzzard]]s as well as abandoned [[eagle]] nests.<ref name= Voous/> Unlike other northerly breeding raptorial birds, the snowy owl is not known to nest on cliffs and the like, so do not enter into direct competition with eagles, falcons, ravens or other ''Bubo'' owls when nesting to the relative south.<ref name= Voous/> The area of nest mound often has a relatively rich plant life which attract the lemmings, which may tunnel right under and around the owl's nest.<ref name= Voous/> [[Goose|Geese]], ducks and [[shorebird]]s of several species known to gain incidental protection by nesting close to snowy owls. Conversely, the snowy owls will sometimes kill and eat both young and adults of these birds, which implies a trade-off in the benefits.<ref name= Parmelee/><ref name= Murie/><ref name= Robinson/><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v109n03/p0449-p0461.pdf|author=Tremblay, J. P., Gauthier, G., Lepage, D., & Desrochers, A. |year=1997|title=Factors affecting nesting success in greater snow geese: Effects of habitat and association with snowy owls|journal= The Wilson Bulletin|pages= 449–461|volume=109|issue=3|jstor=4163840}}</ref><ref>{{cite journal|doi=10.1139/z96-210}}</ref><ref>{{cite journal|doi=10.1007/BF02465456|title=How do Brent Geese (''Branta b. bernicla'') cope with evil}}</ref><ref>Smith, P. A. (2003). ''Factors affecting nest site selection and reproductive success of tundra nesting shorebirds'' (Doctoral dissertation, University of British Columbia).</ref>
Most individuals arrive at the nest site by April or May with a few overwintering arctic exceptions.<ref name= Murie/><ref name= Marine/><ref name= Pitelka2/> Males advertises potential nest sites to his mate by scratching the ground and spreading his wings over it.<ref name= Konig/> The nest is usually a shallow depression on a windswept eminence in the open tundra. There seems to be a variety of qualifiers for appropriate nest sites. The nest site is typically snow-free and dry relative to the surrounding environment, usually with a good view of the surrounding landscape. The nest may be made of [[ridge]]s, [[Mound|elevated mound]]s, high [[polygon]]s, [[hummock]]s, hills, man-made mounds and occasionally [[Outcrop|rocky outcrops]]. If covered with vegetation, taller plants that may obstruct view are plucked away sometimes.<ref name= Konig/><ref name= Voous/><ref name= Watson/><ref name= Pitelka2/><ref name= Holt3>{{cite journal|doi=10.5253/078.097.0422}}</ref> The nest sites are often long-established and naturally created by the freeze-thaw process of the tundra.<ref name= Voous/><ref name= Holt/> [[Bar (river morphology)|Gravel bars]] may be used as well.<ref name= Potapov/> The female may take the most active role in the nest's condition of any owl species.<ref name= Holt/><ref name= Mikkola/> No owl build their own nests but female snowy owls take about three days constructing a scrape, digging with her claws and rotating until a fairly circular bowl is formed. She will still not construct or add foreign materials to the nest (despite some circumstantial evidence of moss and grass from outside the nest mound being found).<ref name= Holt/><ref name= Murie/><ref name= Tulloch/> In two separate cases in Utqiaġvik, two separate females dug out a second scrape to the side and below the main nests and appeared to have called all chicks to the more secluded nest to ride out severe weather until the skies cleared.<ref name= Holt/> The Utqiaġvik nest scrapes averaged {{convert|47.7|x|44|cm|in|abbr=on}} in 91 with a mean depth of {{convert|9.8|cm|in|abbr=on}} while the scrapes were smaller in [[Hooper Bay]], reportedly {{convert|25|to|33|cm|in|abbr=on}} diameter and {{convert|4|to|9|cm|in|abbr=on}} in depth.<ref name= Murie/><ref name= Holt3/> Occasionally, in the lower tundra, snowy owls may too use old nests of [[rough-legged buzzard]]s as well as abandoned [[eagle]] nests.<ref name= Voous/> Unlike other northerly breeding raptorial birds, the snowy owl is not known to nest on cliffs and the like, so do not enter into direct competition with eagles, falcons, ravens or other ''Bubo'' owls when nesting to the relative south.<ref name= Voous/> The area of nest mound often has a relatively rich plant life which attract the lemmings, which may tunnel right under and around the owl's nest.<ref name= Voous/> [[Goose|Geese]], ducks and [[shorebird]]s of several species known to gain incidental protection by nesting close to snowy owls. Conversely, the snowy owls will sometimes kill and eat both young and adults of these birds, which implies a trade-off in the benefits.<ref name= Parmelee/><ref name= Murie/><ref name= Robinson/><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v109n03/p0449-p0461.pdf|author=Tremblay, J. P., Gauthier, G., Lepage, D., & Desrochers, A. |year=1997|title=Factors affecting nesting success in greater snow geese: Effects of habitat and association with snowy owls|journal= The Wilson Bulletin|pages= 449–461|volume=109|issue=3|jstor=4163840}}</ref><ref>{{cite journal|doi=10.1139/z96-210}}</ref><ref>{{cite journal|doi=10.1007/BF02465456|title=How do Brent Geese (''Branta b. bernicla'') cope with evil}}</ref><ref>Smith, P. A. (2003). ''Factors affecting nest site selection and reproductive success of tundra nesting shorebirds'' (Doctoral dissertation, University of British Columbia).</ref>


===Eggs===
===Eggs===
===Parental behavior===
===Parental behavior===
[[File:SnowyOwl2.jpg|thumb|left|A captive mother snowy owl with its chick.]]
[[File:SnowyOwl2.jpg|thumb|left|A captive mother snowy owl with its chick.]]
Food is brought to the nest by males and surplus food is stored nearby.<ref name= Konig/> Females in breeding season often develop a very extensive [[brood patch]] which in this species is a fairly enormous, high vascularized featherless area of pink belly skin.<ref name= Voous/><ref name= Parmelee/> Incubation lasts 31.8–33 days (unconfirmed and possibly dubious reports from as little as 27 to as much as 38-day incubations).<ref name= Konig/><ref name= Murie/><ref name= Robinson/><ref name= Schaanning/> The female alone broods the young, often while simultaneously incubating still unhatched eggs.<ref name= Konig/><ref name= Holt/> Sometimes older chicks incidentally brood their younger siblings and females may shelter the young under her wings during inclement weather.<ref name= Parmelee/><ref name= Watson/> When first feeding the young, the female may dismantle prey to feed the young only the softer body parts then gradually ramping up the size of proportions until they eat a whole prey item.<ref name= Watson/> Aggressive encounters with parent snowy owls are said to be "genuinely dangerous" and one resource claimed the snowy owl to be the bird species with the most formidable nest defense displays towards humans.<ref name= Voous/><ref name= Bent/><ref>Couzens, D. (2008). ''Extreme Birds: The World's Most Extraordinary and Bizarre Birds''. Firefly Books.</ref> The usual response to sighted humans near the nest is mild but continued approach begins to increasingly irritate the parents.<ref name= Holt/> At times, humans are forcefully dive-bombed upon, while other potential threats are dealt with in a “forward-threat” where the male walks towards the intruders, engaging in impressive feather-raising and fanning out of half-spread wings until they run forward and slash with both their feet and bill.<ref name= Voous/><ref name= Bent/><ref name= Watson/><ref name= Sutton1/><ref name= Parmelee/> Fairly serious injuries have been sustained in the worst of snowy owl defensive attacks, including cranial trauma, requiring researchers to make the long trek back to medical care, although human fatalities are not known.<ref name= Sutton/><ref>Barth, E. K. (1950). ''Efter fjallugglor pf Hardangervidda''. Fauna Flora, 45: 235–242.</ref> Snowy owl parents have been seen to aggressively attacked glaucous gulls, arctic fox and dogs in breeding ground in Utqiaġvik.<ref name= Holt/> Non-predatory animals like [[Reindeer|caribou]] in Utqiaġvik and sheep (''Ovis aries'') in Fetlar are attacked as well, possibly to avoid potential trampling of the eggs or the young.<ref name= Parmelee/><ref name= Tulloch/> Males are said to do the majority of nest defense but the female will also often become involved as well.<ref name= Holt/> Analysis showed in [[Lapland, Sweden]], that females in nest defense against people engaged in vocal displays (warning and mewing calls) and that males did not engage in mewing but did engage in most hooting calls, many warning calls and almost all physical attacks.<ref name= Wiklund>Wiklund, C. G., & Stigh, J. (1983). ''Nest defence and evolution of reversed sexual size dimorphism in Snowy Owls Nyctea scandiaca''. Ornis Scandinavica, 58–62.</ref> In other instances, [[distraction display]]s are engaged in against predators, with a "broken-wing act" including high, thin squeals interspersed with weird squeaks, often taking flight only to quickly fall from the sky and imitate a struggle.<ref name= Voous/><ref>[http://animaldiversity.ummz.umich.edu/site/accounts/information/Nyctea_scandiaca.html ADW: ''Nyctea scandiaca: Information'']. Animaldiversity.ummz.umich.edu. Retrieved on 19 October 2010.</ref> One author recorded a male to draw him about {{convert|2|km|mi|abbr=on}} from the nest before ceasing.<ref name= Parmelee/> 77% of 45 distraction displays in Lapland, Sweden were by females.<ref name= Wiklund/>
Food is brought to the nest by males and surplus food is stored nearby.<ref name= Konig/> Females in breeding season often develop a very extensive [[brood patch]] which in this species is a fairly enormous, high vascularized featherless area of pink belly skin.<ref name= Voous/><ref name= Parmelee/> Incubation lasts 31.8–33 days (unconfirmed and possibly dubious reports from as little as 27 to as much as 38-day incubations).<ref name= Konig/><ref name= Murie/><ref name= Robinson/><ref name= Schaanning/> The female alone broods the young, often while simultaneously incubating still unhatched eggs.<ref name= Konig/><ref name= Holt/> Sometimes older chicks incidentally brood their younger siblings and females may shelter the young under her wings during inclement weather.<ref name= Parmelee/><ref name= Watson/> When first feeding the young, the female may dismantle prey to feed the young only the softer body parts then gradually ramping up the size of proportions until they eat a whole prey item.<ref name= Watson/> Aggressive encounters with parent snowy owls are said to be "genuinely dangerous" and one resource claimed the snowy owl to be the bird species with the most formidable nest defense displays towards humans.<ref name= Voous/><ref name= Bent/><ref>Couzens, D. (2008). ''Extreme Birds: The World's Most Extraordinary and Bizarre Birds''. Firefly Books.</ref> The usual response to sighted humans near the nest is mild but continued approach begins to increasingly irritate the parents.<ref name= Holt/> At times, humans are forcefully dive-bombed upon, while other potential threats are dealt with in a “forward-threat” where the male walks towards the intruders, engaging in impressive feather-raising and fanning out of half-spread wings until they run forward and slash with both their feet and bill.<ref name= Voous/><ref name= Bent/><ref name= Watson/><ref name= Sutton1/><ref name= Parmelee/> Fairly serious injuries have been sustained in the worst of snowy owl defensive attacks, including cranial trauma, requiring researchers to make the long trek back to medical care, although human fatalities are not known.<ref name= Sutton/> Snowy owl parents have been seen to aggressively attacked glaucous gulls, arctic fox and dogs in breeding ground in Utqiaġvik.<ref name= Holt/> Non-predatory animals like [[Reindeer|caribou]] in Utqiaġvik and sheep (''Ovis aries'') in Fetlar are attacked as well, possibly to avoid potential trampling of the eggs or the young.<ref name= Parmelee/><ref name= Tulloch/> Males are said to do the majority of nest defense but the female will also often become involved as well.<ref name= Holt/> Analysis showed in [[Lapland, Sweden]], that females in nest defense against people engaged in vocal displays (warning and mewing calls) and that males did not engage in mewing but did engage in most hooting calls, many warning calls and almost all physical attacks.<ref name= Wiklund>{{cite journal|title=Nest defence and evolution of reversed sexual size dimorphism in Snowy Owls ''Nyctea scandiaca''|doi=10.2307/3676252}}</ref> In other instances, [[distraction display]]s are engaged in against predators, with a "broken-wing act" including high, thin squeals interspersed with weird squeaks, often taking flight only to quickly fall from the sky and imitate a struggle.<ref name= Voous/><ref>[http://animaldiversity.ummz.umich.edu/site/accounts/information/Nyctea_scandiaca.html ADW: ''Nyctea scandiaca: Information'']. Animaldiversity.ummz.umich.edu. Retrieved on 19 October 2010.</ref> One author recorded a male to draw him about {{convert|2|km|mi|abbr=on}} from the nest before ceasing.<ref name= Parmelee/> 77% of 45 distraction displays in Lapland, Sweden were by females.<ref name= Wiklund/>


===Development of young===
===Development of young===
[[File:Young snowy owls (69120).jpg|thumb|An old photo of snowy owl nestlings on [[Baffin Island]].]]
[[File:Young snowy owls (69120).jpg|thumb|An old photo of snowy owl nestlings on [[Baffin Island]].]]
Hatching intervals are generally from 1 to 3 days, quite often within 37–45 hours apart.<ref name= Watson/><ref name= Tulloch/> New chicks are [[Altriciality|semi-altricial]] (i.e. typically helpless and blind), initially being white and rather wet but dry by the end of the first day. The weight of 7 hatchlings was {{convert|35|to|55|g|oz|abbr=on}}, with an average of {{convert|46|g|oz|abbr=on}} while 3 were {{convert|44.7|g|oz|abbr=on}}.<ref name= Parmelee/><ref name= Watson/> Due to the pronounced asynchrony of the egg-laying and hatching, the size difference between siblings can be enormous and in some cases when the smallest chick weighs only {{convert|20|to|50|g|oz|abbr=on}}, the biggest chick already has attained a weight of around {{convert|350|to|380|g|oz|abbr=on}}.<ref name= Watson/><ref name= Barth/> When the oldest chick is about 3 weeks, the female will start to hunt as well as the male and both may directly feed the young although in some cases they may not need hunt very much if lemmings are particularly numerous.<ref name= Konig/><ref name= Voous/> [[Hoarding (animal behavior)|Caches]] of lemmings around a nest may include more than 80 lemmings that can support the family.<ref name= Voous/> Unlike many owls, the chicks of snowy owls are not known to behave aggressively toward one another or to engage in [[siblicide]], perhaps in part due to the need for energy conservance.<ref name= Holt/><ref name= Tulloch/> Some cases of [[cannibalism]] of chicks by the family group were thought to be cases where chicks die from other causes.<ref name= Sutton/> When they are about 2 weeks, the chicks may begin to walk around the nest site which they leave by 18–28 days, although they are still unable to fly and may find safety in nooks and crannies of vegetation and rocks usually only about {{convert|1|to|2|m|ft|abbr=on}} from the nest mound, as well as via their parents defense.<ref name= Konig/><ref name= Voous/><ref name= Romero>Romero, L. M., Holt, D. W. Maples M. & Wingfield, J. C.. (2006). ''Corticosterone is not correlated with nest departure in Snowy Owl chicks (Nyctea scandiaca)''. General and Comparative Endocrinology 149 (2): 119–123.</ref> Leaving the nest is thought to likely be an anti-predator strategy.<ref name= Holt/><ref>Holt, D. W. & Leasure, S. M. (1993). ''Short-eared Owl (Asio flammeus)''. In: ''The birds of North America, No. 62'', edited by A. Poole and F. Gill. Washington, DC: Acad. Nat. Sci., Philadelphia, PA; Am. Ornithol. Union.</ref> The male snowy owl may drop fresh prey deliveries directly on the ground near the wandering young.<ref name= Voous/> After about three weeks of age, the young may wander fairly widely, rarely to {{convert|1|km|mi|abbr=on}}, but usually stay within {{convert|500|m|ft|abbr=on}} of the nest mound.<ref name= Watson/><ref name= Tulloch/> Threat postures by young in reaction to researchers were first noticeable at about 20–25 days of age and common at about 28 days and the chicks can be impressively quick and agile-footed.<ref name= Holt/><ref name= Watson/> The first fledgling occurs at around 35–50 days, and by 50–60 days the young can fly well and hunt on their own.<ref name= Konig/><ref name= Voous/> The total care period is for 2–3.5 months, increasing in length with increased size of the brood.<ref name= Konig/><ref name= Parmelee/> Although independence was once thought to be sought by late August or early September but is more likely by late September to October when migration season for the species begins.<ref name= Holt/><ref name= Pitelka2/> The nesting cycle is similar in length to the Arctic short-eared owls and faster than Eurasian eagle-owls by up to 2 months.<ref name= Schrezinger>Schrezinger, W. (1974). ''Zur Ethologie und Jugendentwicklung der Schnee-Eule Nyctea scandiaca nach Beobachtungen in Gefangenschaft''. J. Orn, 115: 8–49.</ref>
Hatching intervals are generally from 1 to 3 days, quite often within 37–45 hours apart.<ref name= Watson/><ref name= Tulloch/> New chicks are [[Altriciality|semi-altricial]] (i.e. typically helpless and blind), initially being white and rather wet but dry by the end of the first day. The weight of 7 hatchlings was {{convert|35|to|55|g|oz|abbr=on}}, with an average of {{convert|46|g|oz|abbr=on}} while 3 were {{convert|44.7|g|oz|abbr=on}}.<ref name= Parmelee/><ref name= Watson/> Due to the pronounced asynchrony of the egg-laying and hatching, the size difference between siblings can be enormous and in some cases when the smallest chick weighs only {{convert|20|to|50|g|oz|abbr=on}}, the biggest chick already has attained a weight of around {{convert|350|to|380|g|oz|abbr=on}}.<ref name= Watson/> When the oldest chick is about 3 weeks, the female will start to hunt as well as the male and both may directly feed the young although in some cases they may not need hunt very much if lemmings are particularly numerous.<ref name= Konig/><ref name= Voous/> [[Hoarding (animal behavior)|Caches]] of lemmings around a nest may include more than 80 lemmings that can support the family.<ref name= Voous/> Unlike many owls, the chicks of snowy owls are not known to behave aggressively toward one another or to engage in [[siblicide]], perhaps in part due to the need for energy conservance.<ref name= Holt/><ref name= Tulloch/> Some cases of [[cannibalism]] of chicks by the family group were thought to be cases where chicks die from other causes.<ref name= Sutton/> When they are about 2 weeks, the chicks may begin to walk around the nest site which they leave by 18–28 days, although they are still unable to fly and may find safety in nooks and crannies of vegetation and rocks usually only about {{convert|1|to|2|m|ft|abbr=on}} from the nest mound, as well as via their parents defense.<ref name= Konig/><ref name= Voous/><ref name= Romero>Romero, L. M., Holt, D. W. Maples M. & Wingfield, J. C.. (2006). ''Corticosterone is not correlated with nest departure in Snowy Owl chicks (Nyctea scandiaca)''. General and Comparative Endocrinology 149 (2): 119–123.</ref> Leaving the nest is thought to likely be an anti-predator strategy.<ref name= Holt/><ref>Holt, D. W. & Leasure, S. M. (1993). ''Short-eared Owl (Asio flammeus)''. In: ''The birds of North America, No. 62'', edited by A. Poole and F. Gill. Washington, DC: Acad. Nat. Sci., Philadelphia, PA; Am. Ornithol. Union.</ref> The male snowy owl may drop fresh prey deliveries directly on the ground near the wandering young.<ref name= Voous/> After about three weeks of age, the young may wander fairly widely, rarely to {{convert|1|km|mi|abbr=on}}, but usually stay within {{convert|500|m|ft|abbr=on}} of the nest mound.<ref name= Watson/><ref name= Tulloch/> Threat postures by young in reaction to researchers were first noticeable at about 20–25 days of age and common at about 28 days and the chicks can be impressively quick and agile-footed.<ref name= Holt/><ref name= Watson/> The first fledgling occurs at around 35–50 days, and by 50–60 days the young can fly well and hunt on their own.<ref name= Konig/><ref name= Voous/> The total care period is for 2–3.5 months, increasing in length with increased size of the brood.<ref name= Konig/><ref name= Parmelee/> Although independence was once thought to be sought by late August or early September but is more likely by late September to October when migration season for the species begins.<ref name= Holt/><ref name= Pitelka2/> The nesting cycle is similar in length to the Arctic short-eared owls and faster than Eurasian eagle-owls by up to 2 months.<ref name= Schrezinger>Schrezinger, W. (1974). ''Zur Ethologie und Jugendentwicklung der Schnee-Eule Nyctea scandiaca nach Beobachtungen in Gefangenschaft''. J. Orn, 115: 8–49.</ref>


===Maturity and nesting success===
===Maturity and nesting success===
[[File:SNOWY OWL, Canada.jpg|thumb|left|Snowy owl, juvenile, in Ontario, Canada.]]
[[File:SNOWY OWL, Canada.jpg|thumb|left|Snowy owl, juvenile, in Ontario, Canada.]]
Sexual maturity reached the following year but the first breeding is normally at no sooner than the end of the second year of life.<ref name= Konig/> There is little strong evidence of typical age of first breeding but initial breeding by males could be inferred by the plumage of males in Utqiaġvik by plumage. At that stage, which the males were essentially all pure white, most were aged to about 3 to 4 years old.<ref name= Holt/> The snowy owl seems to markedly inconsistent in regard to breeding every year, often taking at least up to two years between attempts and sometimes as much as nearly a decade.<ref name= Potapov/><ref name= Fuller/> 7 satellite-marking females in Canada proved that they did breed in consecutive years, with 1 breeding over 3 consecutive years.<ref name= Therrien/> In 23 years at Utqiaġvik, snowys bred in 13 of them.<ref name= Holt/><ref name= Fuller/> Nesting success can reach 90–100% in even the largest clutches in high lemming years.<ref name= Voous/> While over the course of 21 years, 260 total nests were recorded in Utqiaġvik. There, from 4–54 nests were recorded annually. The Utqiaġvik nests bore 3 to 10 sized-clutches with a mean of 6 eggs per nest and an annual mean hatching success from 39 to 91%. 31–87% of chicks were able to depart on foot and 48–65% were annually estimated to survive to fledge; elsewhere, 40% survived to fledge.<ref name= Holt/><ref name= Parmelee/> In another set, 97% of observed eggs both hatched and fledged.<ref name= Watson/> In Norway, the fledging success from 10 nests was much lower at about 46%.<ref name= Hagen/> Norwegian data, which previously indicated it to be an almost accidental breeder in northern Norway, indicates that it is a more regular breeder than expected, though. 3 good years were found for snowy owls between 1968 and 2005: 1974 (when there were 12 pairs), 1978 (22 pairs) and 1985 (20 pairs), with 14 additional locations when potential (but not confirmed) breeding has occurred.<ref name= Jacobsen/> The main determinable causes of nest failure were deemed to be [[starvation]] and [[Hypothermia|exposure]].<ref name= Holt/> A number of Norwegian and Finnish nests were known to fail due to severe [[black fly]] parasitism.<ref>Solheim, R., Jacobsen, K. O., Øien, I. J., Aarvak, T., & Polojärvi, P. (2013). ''Snowy Owl nest failures caused by blackfly attacks on incubating females''. Ornis Norvegica, 36, 1–5.</ref>
Sexual maturity reached the following year but the first breeding is normally at no sooner than the end of the second year of life.<ref name= Konig/> There is little strong evidence of typical age of first breeding but initial breeding by males could be inferred by the plumage of males in Utqiaġvik by plumage. At that stage, which the males were essentially all pure white, most were aged to about 3 to 4 years old.<ref name= Holt/> The snowy owl seems to markedly inconsistent in regard to breeding every year, often taking at least up to two years between attempts and sometimes as much as nearly a decade.<ref name= Potapov/> 7 satellite-marking females in Canada proved that they did breed in consecutive years, with 1 breeding over 3 consecutive years.<ref name= Therrien/> In 23 years at Utqiaġvik, snowys bred in 13 of them.<ref name= Holt/> Nesting success can reach 90–100% in even the largest clutches in high lemming years.<ref name= Voous/> While over the course of 21 years, 260 total nests were recorded in Utqiaġvik. There, from 4–54 nests were recorded annually. The Utqiaġvik nests bore 3 to 10 sized-clutches with a mean of 6 eggs per nest and an annual mean hatching success from 39 to 91%. 31–87% of chicks were able to depart on foot and 48–65% were annually estimated to survive to fledge; elsewhere, 40% survived to fledge.<ref name= Holt/><ref name= Parmelee/> In another set, 97% of observed eggs both hatched and fledged.<ref name= Watson/> In Norway, the fledging success from 10 nests was much lower at about 46%.<ref name= Hagen/> Norwegian data, which previously indicated it to be an almost accidental breeder in northern Norway, indicates that it is a more regular breeder than expected, though. 3 good years were found for snowy owls between 1968 and 2005: 1974 (when there were 12 pairs), 1978 (22 pairs) and 1985 (20 pairs), with 14 additional locations when potential (but not confirmed) breeding has occurred. The main determinable causes of nest failure were deemed to be [[starvation]] and [[Hypothermia|exposure]].<ref name= Holt/> A number of Norwegian and Finnish nests were known to fail due to severe [[black fly]] parasitism.<ref>{{cite journal|doi=10.15845/on.v36i0.394}}</ref>


==Longevity==
==Longevity==
The snowy owl can live a long life for a bird.<ref name= Holt/> Records show that the oldest snowy owls in captivity can live to 25 to even 30 years of age.<ref name= Konig/><ref name= Holt/><ref>Schenker, A. (1978). Höchsalter europaischer Vögel im Zoologischen Garten Basel. Ornithol. Beob. 75: 96–97.</ref> Typical lifespans probably reach around 10 years in the wild.<ref name= Konig/><ref name= Mikkola/> The longest known lifespan in the wild was one that initially banded (possibly in its first winter) in [[Massachusetts]] and recovered dead in [[Montana]] 23 years and 10-month later.<ref name= Holt/> The annual survival rate for twelve females on [[Bylot Island]] was estimated at around 85–92.3%.<ref>{{cite journal|doi=10.1002/jwmg.414}}</ref> It is often reputed that snowy owls frequently died from starvation, with historical accounts frequently opined they "had to" leave their breeding grounds due to lemming "crashes" but would starve to the south.<ref name= Kerlinger/><ref name= Gross1/><ref name= Zettenberg>{{cite journal|doi=10.1898/NWN07-19.1}}</ref> However, it was proven fairly early on that snowy owls often do survive throughout the winter.<ref name= Bent/> This is reinforced somewhat by small radio-tracking and banding studies of the northern [[Great Plains]] and the intermountain [[valley]]s of the northwestern United States.<ref name= Zettenberg/><ref name= Kerlinger3>{{cite journal|doi=10.2307/1368844}}</ref> More circumstance evidence shows a lack of starvation in the eastern part of North America as well.<ref>{{cite journal|title=Winter irruptive Snowy Owls (''Bubo scandiacus'') in North America are not starving|doi=10.1139/cjz-2017-0278|url=https://www.researchgate.net/publication/322843463_Winter_irruptive_snowy_owls_in_North_America_are_not_starving}}</ref> There is evidence that some adults are known to return to the same wintering areas in ensuing years, areas which are far south of their breeding range.<ref>{{cite journal|doi=10.29173/bluejay1721}}</ref><ref>{{cite journal|author1=Follen, D. |author2= Luepke, K. |year=1980|title= Snowy Owl recaptures|journal= Inland Bird Banding |volume=52|pages= 60}}</ref> At Logan Airport, most snowy owls that are seen appear to be in good condition.<ref name= Holt/><ref name= Smith/> Of 71 dead snowy owls found in winter in the northern Great Plains, 86% died from assorted [[Major trauma|traumas]], including [[Roadkill|collisions]] with automobiles and other, usually manmade, objects as well as [[electrocution]]s and [[Culling|shootings]]. Only 14% of the 71 deaths were due to apparent starving. Data showed some owls appeared to incur injuries but healed and survived.<ref name= Kerlinger3/> More evidence was found in wintering snowy owls in New York of [[Bone healing|healed fractures]], though some may require surgery to recover.<ref>{{cite journal|pmid=30204018|title=Successful Management of Open, Contaminated Metacarpal Fractures in an Adult Snowy Owl (''Bubo scandiacus'') With a Minimal Type II External Skeletal Fixator}}</ref> 537 wintering birds in Saskatchewan were studied based on [[Fatty acid metabolism|fat reserves]], which were superior in females over males and adults over juveniles; while 31% of females lacked fat reserves, at least 45% of males found starving or in a state of infirmity were males and 63% turned into [[Wildlife rehabilitation]] centres were also males.<ref name= Chang/> In British Columbia, of 177 snowy owl deaths, of owls to die, only a small percentage were due to natural causes, such as assumed starvation at 13% and 12% were "found dead".<ref name= Campbell/> 1 fledgling on Fetlar dead due to [[pneumonia]] and ''[[Staphylococcus]]'' while a second died from ''[[Aspergillosis]]''.<ref name= Robinson/> Evidence shows that in Utqiaġvik during exceptionally prolonged rains (i.e. 2 to 3 days), nest-departed young in Utqiaġvik were vulnerable to starvation, leading to [[hypothermia]] and pneumonia.<ref name= Holt/> Due to their natural history, the snowy owl may be effected more severely by [[Parasitism|blood parasitism]] than other raptors, due to lowered [[Immunity (medical)|immunity]].<ref>{{cite journal|pmid=29517448|title=Clinical effect of hemoparasite infections in snowy owls (''Bubo scandiacus'')}}</ref> Conversely, they appear to have lower levels of ectoparasites like [[Mallophaga|chewing lice]] than in other large owls per large samples from [[Manitoba]]. The snowy owls averaged about 3.9 chewing lice per host against 7.5 for great grey owls and 10.5 for great horned owls.<ref>{{cite journal|doi=10.4039/tce.2019.42|title=Infestation parameters for chewing lice (Phthiraptera: Amblycera, Ischnocera) infesting owls (Aves: Strigidae, Tytonidae) in Manitoba, Canada}}</ref>
The snowy owl can live a long life for a bird.<ref name= Holt/> Records show that the oldest snowy owls in captivity can live to 25 to even 30 years of age.<ref name= Konig/><ref name= Holt/><ref>Schenker, A. (1978). Höchsalter europaischer Vögel im Zoologischen Garten Basel. Ornithol. Beob. 75: 96–97.</ref> Typical lifespans probably reach around 10 years in the wild.<ref name= Konig/><ref name= Mikkola/> The longest known lifespan in the wild was one that initially banded (possibly in its first winter) in [[Massachusetts]] and recovered dead in [[Montana]] 23 years and 10-month later.<ref name= Holt/> The annual survival rate for twelve females on [[Bylot Island]] was estimated at around 85–92.3%.<ref>{{cite journal|doi=10.1002/jwmg.414}}</ref> It is often reputed that snowy owls frequently died from starvation, with historical accounts frequently opined they "had to" leave their breeding grounds due to lemming "crashes" but would starve to the south.<ref name= Kerlinger/><ref name= Gross1/><ref name= Zettenberg>{{cite journal|doi=10.1898/NWN07-19.1}}</ref> However, it was proven fairly early on that snowy owls often do survive throughout the winter.<ref name= Bent/> This is reinforced somewhat by small radio-tracking and banding studies of the northern [[Great Plains]] and the intermountain [[valley]]s of the northwestern United States.<ref name= Zettenberg/><ref name= Kerlinger3>{{cite journal|doi=10.2307/1368844}}</ref> More circumstance evidence shows a lack of starvation in the eastern part of North America as well.<ref>{{cite journal|title=Winter irruptive Snowy Owls (''Bubo scandiacus'') in North America are not starving|doi=10.1139/cjz-2017-0278|url=https://www.researchgate.net/publication/322843463_Winter_irruptive_snowy_owls_in_North_America_are_not_starving}}</ref> There is evidence that some adults are known to return to the same wintering areas in ensuing years, areas which are far south of their breeding range.<ref>{{cite journal|doi=10.29173/bluejay1721}}</ref><ref>{{cite journal|author1=Follen, D. |author2= Luepke, K. |year=1980|title= Snowy Owl recaptures|journal= Inland Bird Banding |volume=52|pages= 60}}</ref> At Logan Airport, most snowy owls that are seen appear to be in good condition.<ref name= Holt/> Of 71 dead snowy owls found in winter in the northern Great Plains, 86% died from assorted [[Major trauma|traumas]], including [[Roadkill|collisions]] with automobiles and other, usually manmade, objects as well as [[electrocution]]s and [[Culling|shootings]]. Only 14% of the 71 deaths were due to apparent starving. Data showed some owls appeared to incur injuries but healed and survived.<ref name= Kerlinger3/> More evidence was found in wintering snowy owls in New York of [[Bone healing|healed fractures]], though some may require surgery to recover.<ref>{{cite journal|pmid=30204018|title=Successful Management of Open, Contaminated Metacarpal Fractures in an Adult Snowy Owl (''Bubo scandiacus'') With a Minimal Type II External Skeletal Fixator}}</ref> 537 wintering birds in Saskatchewan were studied based on [[Fatty acid metabolism|fat reserves]], which were superior in females over males and adults over juveniles; while 31% of females lacked fat reserves, at least 45% of males found starving or in a state of infirmity were males and 63% turned into [[Wildlife rehabilitation]] centres were also males.<ref name= Chang/> In British Columbia, of 177 snowy owl deaths, of owls to die, only a small percentage were due to natural causes, such as assumed starvation at 13% and 12% were "found dead".<ref name= Campbell/> 1 fledgling on Fetlar dead due to [[pneumonia]] and ''[[Staphylococcus]]'' while a second died from ''[[Aspergillosis]]''.<ref name= Robinson/> Evidence shows that in Utqiaġvik during exceptionally prolonged rains (i.e. 2 to 3 days), nest-departed young in Utqiaġvik were vulnerable to starvation, leading to [[hypothermia]] and pneumonia.<ref name= Holt/> Due to their natural history, the snowy owl may be effected more severely by [[Parasitism|blood parasitism]] than other raptors, due to lowered [[Immunity (medical)|immunity]].<ref>{{cite journal|pmid=29517448|title=Clinical effect of hemoparasite infections in snowy owls (''Bubo scandiacus'')}}</ref> Conversely, they appear to have lower levels of ectoparasites like [[Mallophaga|chewing lice]] than in other large owls per large samples from [[Manitoba]]. The snowy owls averaged about 3.9 chewing lice per host against 7.5 for great grey owls and 10.5 for great horned owls.<ref>{{cite journal|doi=10.4039/tce.2019.42|title=Infestation parameters for chewing lice (Phthiraptera: Amblycera, Ischnocera) infesting owls (Aves: Strigidae, Tytonidae) in Manitoba, Canada}}</ref>


==Status==
==Status==
This species presence and numbers is dependent on amount of food available. In "lemming years", snowy owls can appear to be quite abundant in habitat.<ref name= Konig/> Numbers of snowy owls are difficult to estimate even within studies that take place over decades due to the nomadic nature of adults.<ref name= Holt/> The population of [[Scandinavia]] has long been perceived as very small and [[Ephemerality|ephemeral]] with Finland holding 0–100 pairs; Norway holding 1–20 pairs and Sweden holding 1–50 pairs.<ref name= Holt/><ref name= Jacobsen/><ref>Väisänen, R. A., Lammi, E., & Koskimies, P. (1998). ''Distribution, numbers and population changes of Finnish breeding birds''. Otava, Helsinki, Finland.</ref><ref name= Saurola>{{cite journal|doi=10.5253/078.097.0411}}</ref> A low breeding population within [[European Russia]] has been estimated to hold 1,300–4,500 pairs and Greenland to have 500–1,000 pairs.<ref>BirdLife International (2015). ''European Red List of Birds''. Office for Official Publications of the European Communities, Luxembourg</ref><ref>{{cite journal|doi=10.3312/jyio.44.1|title=Cross-species amplification of microsatellite markers in the Great Horned Owl ''Bubo virginianus'', Short-eared Owl ''Asio flammeus'' and Snowy Owl ''B. scandiacus'' for use in population genetics, individual identification and parentage studies}}</ref> Other than northern part of the American continent, a majority of the snowy owl's breeding range is in northern Russia, but overall estimates are not known.<ref name= Holt/><ref>Stepanyan, L.S. (1990). ''Konspekt ornitologicheskoi fauny SSSR. [Conspectus of the Ornithological Fauna of the USSR]''. Nauka, Moscow. (In Russian with English summary.).</ref> An exact count of 4,871 individuals were seen on surveys between the [[Indigirka River|Indigirka]] and [[Kolyma river]]s.<ref name= Potapov/> The numbers estimated by Partners in Flight and other authors by the 2000s was that North America held about 72,500 snowy owls, about 30% of which were juveniles.<ref>Rich, T. D., Beardmore, C. J. Berlanga, H., Blancher, P. J., Bradstreet, M. S. W., Butcher, G. S., Demarest, D. W., Dunn, E. H., Hunter, W. C., Iñigo-Elias, E. E., Kennedy, J. A., Martell, A. M.. Panjabi, A. O., Pashley, D. N., Rosenberg, K. V., Rustay, C. M., Wendt, J. S. & Will, T. C. (2004). ''Partners in Flight North American Landbird Conservation Plan''. Cornell Lab of Ornithology, Ithaca, NY, USA.</ref><ref>{{cite journal|doi=10.2193/0091-7648(2006)34[1392:EOFHOW]2.0.CO;2}}</ref> The Canadian population of snowy owls was estimated at 10,000–30,000 (in the 1990s) or even to 50,000–100,000 individuals, perhaps improbably.<ref>{{cite journal|author=Kirk, D. A., Hussell D. & Dunn, E. |year=1995|title=Raptor population status and trends in Canada|journal= Bird Trends|volume= 4|pages= 2–9}}</ref><ref>Reding-License, A. A. (2015). Harfang des neiges (''Bubo scandiacus''). Government of Canada.</ref><ref>American Ornithologists' Union (1998). ''Check-list of North American Birds, 7th edition''. American Ornithologists' Union, Washington, DC, USA.</ref> Within Canada, the population on [[Banks Island]] was once claimed at up to 15,000–25,000 in productive years and in [[Queen Elizabeth Islands]] at about 932 individuals.<ref name= Manning/><ref>Miller, F. L. (1987). ''Snowy Owl numbers on twelve Queen Elizabeth Islands, Canadian High Arctic''. Journal of Raptor Research 21 (4): 153–157.</ref> Alaska is the only state with breeding snowy owls but has probably quite a bit fewer breeding owls than does Canada.<ref>Alaska Department of Fish and Game. State of Alaska special status species 2011.</ref> Furthermore, the Partners in Flight and the [[IUCN]] estimated that the world population was roughly 200,000–290,000 individuals as recently as the 2000s.<ref>PIFSC. ''Partners in Flight Science Committee (2013)''. Population estimates database (Version 2.0) 2013. Available from http://rmbo.org/pifpopestimates.</ref><ref>BirdLife International. ''Nyctea Scandiaca''. 2006 IUCN Red List of Threatened Species (2004). Available from http://www.iucnredlist.org.</ref><ref>Burton, J. A. (1973). ''Owls of the world''. New York: E. P. Dutton.</ref> However, in the 2010s, it has been discovered that all prior estimates were extremely excessive and that more precise numbers could be estimated with better surveying, [[Phylogeography|phylogeographic data]] and more insights into the owl's free-wheeling wanderings.<ref name="iucn status 19 November 2021" /><ref name= Holt/> It is now believed that there are only 14,000–28,000 mature breeding pairs of snowy owls in the world.<ref name= Holt/><ref name= Marthinsen/> During lemming declines, the number of nesting females may drop down to as low as 1,700 worldwide, a dangerously low number, and the number of snowy owls worldwide is less than 10% of what it was once thought to be.<ref name= Holt/><ref name= Marthinsen/><ref>{{cite journal|doi=10.2307/1527}}</ref> Due to the small and rapidly declining population, the snowy was uplisted in 2017 to being a [[vulnerable species]] by the [[IUCN]].<ref name="iucn status 19 November 2021" /> A 52% decline has been inferred for the North American population since the 1960s with another even more drastic estimate placing the decline from 1970 to 2014 at 64%.<ref>Berlanga, H., Kennedy, J. A., Rich, T. D., Arizmendi, M. C., Beardmore, C. J., Blancher, P. J., Butcher, G. S., Couturier, A. R., Dayer, A. A., Demarest, D. W., Easton, W. E., Gustafson, M., Iñigo-Elias, E., Krebs, E. A., Panjabi, A. O., Rodriguez Contreras, V., Rosenberg, K. V., Ruth, J. M., Santana Castellón, E., Vidal, R. Ma. & Will, T. (2010). ''Saving our shared birds: Partners in Flight tri-national vision for landbird conservation''. Ithaca: Cornell Laboratory of Ornithology.</ref><ref>Rosenberg, K. V., Blancher, P. J., Stanton, J. C., & Panjabi, A. O. (2017). ''Use of North American Breeding Bird Survey data in avian conservation assessments''. The Condor: Ornithological Applications, 119(3), 594–606.</ref> Trends are harder to delineate in Scandinavia but a similar downward trend is thought to be occurring.<ref name= Holt/><ref name= Jacobsen/><ref name= Saurola/>
This species presence and numbers is dependent on amount of food available. In "lemming years", snowy owls can appear to be quite abundant in habitat.<ref name= Konig/> Numbers of snowy owls are difficult to estimate even within studies that take place over decades due to the nomadic nature of adults.<ref name= Holt/> The population of [[Scandinavia]] has long been perceived as very small and [[Ephemerality|ephemeral]] with Finland holding 0–100 pairs; Norway holding 1–20 pairs and Sweden holding 1–50 pairs.<ref name= Holt/><ref name= Saurola>{{cite journal|doi=10.5253/078.097.0411}}</ref> A low breeding population within [[European Russia]] has been estimated to hold 1,300–4,500 pairs and Greenland to have 500–1,000 pairs.<ref>BirdLife International (2015). ''European Red List of Birds''. Office for Official Publications of the European Communities, Luxembourg</ref><ref>{{cite journal|doi=10.3312/jyio.44.1|title=Cross-species amplification of microsatellite markers in the Great Horned Owl ''Bubo virginianus'', Short-eared Owl ''Asio flammeus'' and Snowy Owl ''B. scandiacus'' for use in population genetics, individual identification and parentage studies}}</ref> Other than northern part of the American continent, a majority of the snowy owl's breeding range is in northern Russia, but overall estimates are not known.<ref name= Holt/><ref>Stepanyan, L.S. (1990). ''Konspekt ornitologicheskoi fauny SSSR. [Conspectus of the Ornithological Fauna of the USSR]''. Nauka, Moscow. (In Russian with English summary.).</ref> An exact count of 4,871 individuals were seen on surveys between the [[Indigirka River|Indigirka]] and [[Kolyma river]]s.<ref name= Potapov/> The numbers estimated by Partners in Flight and other authors by the 2000s was that North America held about 72,500 snowy owls, about 30% of which were juveniles.<ref>Rich, T. D., Beardmore, C. J. Berlanga, H., Blancher, P. J., Bradstreet, M. S. W., Butcher, G. S., Demarest, D. W., Dunn, E. H., Hunter, W. C., Iñigo-Elias, E. E., Kennedy, J. A., Martell, A. M.. Panjabi, A. O., Pashley, D. N., Rosenberg, K. V., Rustay, C. M., Wendt, J. S. & Will, T. C. (2004). ''Partners in Flight North American Landbird Conservation Plan''. Cornell Lab of Ornithology, Ithaca, NY, USA.</ref><ref>{{cite journal|doi=10.2193/0091-7648(2006)34[1392:EOFHOW]2.0.CO;2}}</ref> The Canadian population of snowy owls was estimated at 10,000–30,000 (in the 1990s) or even to 50,000–100,000 individuals, perhaps improbably.<ref>{{cite journal|author=Kirk, D. A., Hussell D. & Dunn, E. |year=1995|title=Raptor population status and trends in Canada|journal= Bird Trends|volume= 4|pages= 2–9}}</ref><ref>Reding-License, A. A. (2015). Harfang des neiges (''Bubo scandiacus''). Government of Canada.</ref><ref>American Ornithologists' Union (1998). ''Check-list of North American Birds, 7th edition''. American Ornithologists' Union, Washington, DC, USA.</ref> Within Canada, the population on [[Banks Island]] was once claimed at up to 15,000–25,000 in productive years and in [[Queen Elizabeth Islands]] at about 932 individuals.<ref name= Manning/><ref>Miller, F. L. (1987). ''Snowy Owl numbers on twelve Queen Elizabeth Islands, Canadian High Arctic''. Journal of Raptor Research 21 (4): 153–157.</ref> Alaska is the only state with breeding snowy owls but has probably quite a bit fewer breeding owls than does Canada.<ref>Alaska Department of Fish and Game. State of Alaska special status species 2011.</ref> Furthermore, the Partners in Flight and the [[IUCN]] estimated that the world population was roughly 200,000–290,000 individuals as recently as the 2000s.<ref>PIFSC. ''Partners in Flight Science Committee (2013)''. Population estimates database (Version 2.0) 2013. Available from http://rmbo.org/pifpopestimates.</ref><ref>BirdLife International. ''Nyctea Scandiaca''. 2006 IUCN Red List of Threatened Species (2004). Available from http://www.iucnredlist.org.</ref><ref>Burton, J. A. (1973). ''Owls of the world''. New York: E. P. Dutton.</ref> However, in the 2010s, it has been discovered that all prior estimates were extremely excessive and that more precise numbers could be estimated with better surveying, [[Phylogeography|phylogeographic data]] and more insights into the owl's free-wheeling wanderings.<ref name="iucn status 19 November 2021" /><ref name= Holt/> It is now believed that there are only 14,000–28,000 mature breeding pairs of snowy owls in the world.<ref name= Holt/><ref name= Marthinsen/> During lemming declines, the number of nesting females may drop down to as low as 1,700 worldwide, a dangerously low number, and the number of snowy owls worldwide is less than 10% of what it was once thought to be.<ref name= Holt/><ref name= Marthinsen/><ref name=chitty>{{cite journal|doi=10.2307/1527}}</ref> Due to the small and rapidly declining population, the snowy was uplisted in 2017 to being a [[vulnerable species]] by the [[IUCN]].<ref name="iucn status 19 November 2021" /> A 52% decline has been inferred for the North American population since the 1960s with another even more drastic estimate placing the decline from 1970 to 2014 at 64%.<ref>{{cite journal|doi=10.1650/CONDOR-17-57.1}}</ref> Trends are harder to delineate in Scandinavia but a similar downward trend is thought to be occurring.<ref name= Holt/><ref name= Saurola/>


===Anthropogenic mortality and persecution===
===Anthropogenic mortality and persecution===
Of 438 band encounters in the USG banding laboratory, almost all causes of death that could be determined, whether intentional or not, were correlated with human interference.<ref name= Holt/> 34.2% or 150 were dead due to unknown causes, 11.9% were shot, 7.1% were hit by automobiles, 5.5% were found dead or injured on highways, 3.9% were collision from towers or wires, 2.7% were in animal traps, 2.1% in airplane [[birdstrike]]s, 0.6% were [[Wire obstacle|entangled]] while the remaining 33.3% recovered injured due to assorted or unknown causes.<ref name= Holt/> Snowy owls are endangered by heavy airport usage resulting in [[birdstrike]]s. Many such collisions are known in Canada and likely also in [[Siberia]] and Mongolia .<ref name= Catling>{{cite journal|author=Catling, P. M. |year=1973|title=Food of snowy owls wintering in southern Ontario, with particular reference to the snowy owl hazard to aircraft|journal=Ontario field biol|volume= 7|pages= 41–45}}</ref><ref>{{cite journal|doi=10.2307/1367598}}</ref> Despite their danger to planes, no human fatalities have been recorded in collisions with this species.<ref>Blokpoel, H. (1976). ''Bird hazards to aircraft: problems and prevention of bird/aircraft collisions''. Clarke Irwin;[Ottawa]: Canadian Wildlife Service, Environment Canada: Pub. Centre, Supply and Services Canada.</ref> Snowy owls are always far outnumbered in Canadian airports in winter by [[short-eared owl]]s.<ref name= Voous/> However, relative to its scarcity, the snowy accounts for a very large balance of the birdstrikes recorded at American airports due to the attractiveness of the habitat, accounting for 4.6% of 2456 recorded collisions (the barn owl is the most frequently involved in birdstrikes).<ref name= Linnell>{{cite journal|doi=10.3356/JRR-17-64.1}}</ref> The species is locally vulnerable to [[pesticide]]s.<ref name= Konig/> The placement of buildings in the Utqiaġvik is now thought to have displaced some snowy owls.<ref name= Holt3/> In Norway, potential sources of disturbance near the nests include tourism, [[recreation]], [[Reindeer herding|reindeer husbandry]], [[Traffic|motorized traffic]], dogs, photographers, ornithologists and scientists.<ref name= Heggoy/> Some biologist have expressed concern that [[Telemetry|radio-tagging]] of snowy owls may cause some unclear detrimental effect on snowy owls but little evidence is known if they actually make the owls more susceptible to death.<ref>{{cite journal|doi=10.15845/on.v40i0.1309|title=Effects of satellite transmitters on survival in Snowy Owls ''Bubo scandiacus''}}</ref>
Of 438 band encounters in the USG banding laboratory, almost all causes of death that could be determined, whether intentional or not, were correlated with human interference.<ref name= Holt/> 34.2% or 150 were dead due to unknown causes, 11.9% were shot, 7.1% were hit by automobiles, 5.5% were found dead or injured on highways, 3.9% were collision from towers or wires, 2.7% were in animal traps, 2.1% in airplane [[birdstrike]]s, 0.6% were [[Wire obstacle|entangled]] while the remaining 33.3% recovered injured due to assorted or unknown causes.<ref name= Holt/> Snowy owls are endangered by heavy airport usage resulting in [[birdstrike]]s. Many such collisions are known in Canada and likely also in [[Siberia]] and Mongolia .<ref name= Catling>{{cite journal|author=Catling, P. M. |year=1973|title=Food of snowy owls wintering in southern Ontario, with particular reference to the snowy owl hazard to aircraft|journal=Ontario field biol|volume= 7|pages= 41–45}}</ref><ref>{{cite journal|doi=10.2307/1367598}}</ref> Despite their danger to planes, no human fatalities have been recorded in collisions with this species.<ref>Blokpoel, H. (1976). ''Bird hazards to aircraft: problems and prevention of bird/aircraft collisions''. Clarke Irwin;[Ottawa]: Canadian Wildlife Service, Environment Canada: Pub. Centre, Supply and Services Canada.</ref> Snowy owls are always far outnumbered in Canadian airports in winter by [[short-eared owl]]s.<ref name= Voous/> However, relative to its scarcity, the snowy accounts for a very large balance of the birdstrikes recorded at American airports due to the attractiveness of the habitat, accounting for 4.6% of 2456 recorded collisions (the barn owl is the most frequently involved in birdstrikes).<ref name= Linnell>{{cite journal|doi=10.3356/JRR-17-64.1}}</ref> The species is locally vulnerable to [[pesticide]]s.<ref name= Konig/> The placement of buildings in the Utqiaġvik is now thought to have displaced some snowy owls.<ref name= Holt3/> In Norway, potential sources of disturbance near the nests include tourism, [[recreation]], [[Reindeer herding|reindeer husbandry]], [[Traffic|motorized traffic]], dogs, photographers, ornithologists and scientists.<ref name= Heggoy/> Some biologist have expressed concern that [[Telemetry|radio-tagging]] of snowy owls may cause some unclear detrimental effect on snowy owls but little evidence is known if they actually make the owls more susceptible to death.<ref>{{cite journal|doi=10.15845/on.v40i0.1309|title=Effects of satellite transmitters on survival in Snowy Owls ''Bubo scandiacus''}}</ref>


Snowy owls can be quite wary, as they are not infrequently hunted by [[Circumpolar peoples]].<ref name= Voous/> Historically, the snowy owl was one of the most persecuted owl species.<ref name= Holt/> In the irruption of 1876–77, an estimated 500 snowy owls were shot, with similar numbers in 1889–90 and an estimated 500–1,000 killed in [[Ontario]] alone during 1901–02 invasion and about 800 killed in the 1905–06 invasion.<ref name= Bent/> Indigenous people of the Arctic historically killed snowy owls as food but now many communities in northern Alaska are fairly modernized, therefore biologists feel that the permitted killing of snowy owls by the indigenous is outdated.<ref name= Holt/><ref>{{cite journal|url=https://brooklynworks.brooklaw.edu/bjil/vol30/iss2/6/|author=Bakalar, E. M. |year=2004|title=Subsistence Whaling in the Native Village of Barrow: Bringing Autonomy to Native Alaskans Outside the International Whaling Commission|journal= Brook. J. Int'l L.|volume= 30|pages= 601}}</ref> The consumption of snowy owls by humans has been proven as far back as ancient cave deposits in France and elsewhere, and they have even been considered as one of the most frequent food species for early humans.<ref>{{cite journal|url=https://www.researchgate.net/publication/285483173_La_chasse_aux_oiseaux_pendant_la_Prehistoire|author=Mourer-Chauviré, C. |year=1979|title=La chasse aux oiseaux pendant la Préhistoire|journal= La Recherche|volume= 106|issue=10|pages= 1202–1210}}</ref><ref>{{cite journal|doi=10.1016/J.QUAINT.2015.11.146|title=Hunting fast-moving, low-turnover small game: The status of the snowy owl (''Bubo scandiacus'') in the Magdalenian}}</ref> They do not shun developed areas especially with old field that hold rodents and, due to lack of human experience, can be extremely tame and unable to escape armed humans.<ref name= Voous/> In British Columbia, of 177 snowy owl deaths, the most often diagnosed cause of death was shootings at 25%, often well after legal protection of the species.<ref name= Campbell/> The number [[Poaching|poached]] snowy owls in Ontario is opined to be unusually high considering their scarcity.<ref name= Desmarchelier>Desmarchelier, M., Santamaria-Bouvier, A., Fitzgérald, G., & Lair, S. (2010). ''Mortality and morbidity associated with gunshot in raptorial birds from the province of Quebec: 1986 to 2007''. The Canadian Veterinary Journal, 51(1), 70.</ref> While the species was once otherwise killed as food and then later shot out of resentment for perceived threats against domestic and favored game stock, the reasoning behind ongoing shooting of snowy owls into the 21st century is not well-understood.<ref name= Holt/><ref name= Dufresne/><ref name= Desmarchelier/> Siberian snowy owls are frequently victim to [[Bait (luring substance)|baited]] [[Trapping|fox traps]], with possibly up to around 300 killed in a year based upon very rough estimates.<ref>{{cite journal|author=Ellis, D. H. & D. G. Smith|year=1993|title=Preliminary report of extensive Gyrfalcon and Snowy Owl mortality in northern Siberia|journal= Raptor-Link |volume=1 |issue=2|pages=3–4}}</ref> [[Warfarin]] poisoning in use as [[rodenticide]]s are known to kill some wintering snowy owls, including up to six at Logan Airport alone.<ref name= Campbell/><ref name= Smith/><ref>{{cite journal|author=Stone, W. B., Okoniewski, J. C. & Stedelin, J. R. |year=1999|pmid=10231745|title=Poisoning of wildlife with anticoagulant rodenticides in New York|journal= Journal of Wildlife Diseases |volume=35|pages=187–193}}</ref> [[Mercury (element)|Mercury]] concentrations, most likely through [[bioaccumulation]], have been detected in snowy owls in the [[Aleutian Islands]] but it is not known whether fatal [[mercury poisoning]] has occurred.<ref>{{cite journal|doi=10.1016/j.marpolbul.2014.02.034}}</ref> [[Polychlorinated biphenyl|PCB]]s may have killed some snowy owls in concentration.<ref name= Heggoy/> Some airports have advocated and instituted the practice of shooting owls to avoid birdstrikes but successful [[Wildlife translocation|translocation]] is possible and preferred given the species protected status.<ref name= Holt/><ref name= Smith/><ref name= Linnell/>
Snowy owls can be quite wary, as they are not infrequently hunted by [[Circumpolar peoples]].<ref name= Voous/> Historically, the snowy owl was one of the most persecuted owl species.<ref name= Holt/> In the irruption of 1876–77, an estimated 500 snowy owls were shot, with similar numbers in 1889–90 and an estimated 500–1,000 killed in [[Ontario]] alone during 1901–02 invasion and about 800 killed in the 1905–06 invasion.<ref name= Bent/> Indigenous people of the Arctic historically killed snowy owls as food but now many communities in northern Alaska are fairly modernized, therefore biologists feel that the permitted killing of snowy owls by the indigenous is outdated.<ref name= Holt/><ref>{{cite journal|url=https://brooklynworks.brooklaw.edu/bjil/vol30/iss2/6/|author=Bakalar, E. M. |year=2004|title=Subsistence Whaling in the Native Village of Barrow: Bringing Autonomy to Native Alaskans Outside the International Whaling Commission|journal= Brook. J. Int'l L.|volume= 30|pages= 601}}</ref> The consumption of snowy owls by humans has been proven as far back as ancient cave deposits in France and elsewhere, and they have even been considered as one of the most frequent food species for early humans.<ref>{{cite journal|url=https://www.researchgate.net/publication/285483173_La_chasse_aux_oiseaux_pendant_la_Prehistoire|author=Mourer-Chauviré, C. |year=1979|title=La chasse aux oiseaux pendant la Préhistoire|journal= La Recherche|volume= 106|issue=10|pages= 1202–1210}}</ref><ref>{{cite journal|doi=10.1016/J.QUAINT.2015.11.146|title=Hunting fast-moving, low-turnover small game: The status of the snowy owl (''Bubo scandiacus'') in the Magdalenian}}</ref> They do not shun developed areas especially with old field that hold rodents and, due to lack of human experience, can be extremely tame and unable to escape armed humans.<ref name= Voous/> In British Columbia, of 177 snowy owl deaths, the most often diagnosed cause of death was shootings at 25%, often well after legal protection of the species.<ref name= Campbell/> The number [[Poaching|poached]] snowy owls in Ontario is opined to be unusually high considering their scarcity.<ref name= Desmarchelier>Desmarchelier, M., Santamaria-Bouvier, A., Fitzgérald, G., & Lair, S. (2010). ''Mortality and morbidity associated with gunshot in raptorial birds from the province of Quebec: 1986 to 2007''. The Canadian Veterinary Journal, 51(1), 70.</ref> While the species was once otherwise killed as food and then later shot out of resentment for perceived threats against domestic and favored game stock, the reasoning behind ongoing shooting of snowy owls into the 21st century is not well-understood.<ref name= Holt/><ref name= Dufresne/><ref name= Desmarchelier/> Siberian snowy owls are frequently victim to [[Bait (luring substance)|baited]] [[Trapping|fox traps]], with possibly up to around 300 killed in a year based upon very rough estimates.<ref>{{cite journal|author=Ellis, D. H. & D. G. Smith|year=1993|title=Preliminary report of extensive Gyrfalcon and Snowy Owl mortality in northern Siberia|journal= Raptor-Link |volume=1 |issue=2|pages=3–4}}</ref> [[Warfarin]] poisoning in use as [[rodenticide]]s are known to kill some wintering snowy owls, including up to six at Logan Airport alone.<ref name= Campbell/><ref>{{cite journal|author=Stone, W. B., Okoniewski, J. C. & Stedelin, J. R. |year=1999|pmid=10231745|title=Poisoning of wildlife with anticoagulant rodenticides in New York|journal= Journal of Wildlife Diseases |volume=35|pages=187–193}}</ref> [[Mercury (element)|Mercury]] concentrations, most likely through [[bioaccumulation]], have been detected in snowy owls in the [[Aleutian Islands]] but it is not known whether fatal [[mercury poisoning]] has occurred.<ref>{{cite journal|doi=10.1016/j.marpolbul.2014.02.034}}</ref> [[Polychlorinated biphenyl|PCB]]s may have killed some snowy owls in concentration.<ref name= Heggoy/> Some airports have advocated and instituted the practice of shooting owls to avoid birdstrikes but successful [[Wildlife translocation|translocation]] is possible and preferred given the species protected status.<ref name= Holt/><ref name= Linnell/>
[[File:Stare Down Snowy (94026869).jpeg|thumb|right|A potential high risk of electrocution exists for snowy owls in winter.]]
[[File:Stare Down Snowy (94026869).jpeg|thumb|right|A potential high risk of electrocution exists for snowy owls in winter.]]
[[Global warming|Climate change]] is now widely perceived to perhaps the primary driver of the snowy owl's decline. As temperatures continue to rise, abiotic factors such as increased rain and reduced snow are likely to effect lemming populations and, in turn, snowy owls. These and potentially many other issues (possibly including modifying migrating behavior, vegetation composition, increased insect, disease and parasite activities, risk of [[hyperthermia]]) are a matter of concern.<ref name="iucn status 19 November 2021" /><ref name= Holt/><ref name= Heggoy/><ref name= ACIA>ACIA. (2004). ''Impacts of a warming climate: Arctic climate impact assessment''. Cambridge: Cambridge University Press.</ref><ref>Inouye, D. W. (2019). "Climate change in other taxa". ''Effects of Climate Change on Birds'', p. 257. {{ISBN|9780198824268}}</ref> Additionally, reduction of sea ice, which snowy owls are now known to rely extensively on, as a result of warming climates, impacts could be significant.<ref name="iucn status 19 November 2021" /><ref name= Holt/><ref name= Marine/> The effect of [[climate change]] was essentially confirmed in northern Greenland where a perhaps irrevocable collapse of the lemming population was observed. From 1998 to 2000, the lemming numbers appeared to have quickly declined. The number of lemmings per hectare (ha) is less than one-fifth of what it once was in Greenland (i.e. from 12 lemmings per ha to less than 2 per ha at peak). This is almost certainly correlated with a 98% decline in owl productivity as well as that of the local [[Stoat|stoats]] (the [[long-tailed jaeger]] and [[Arctic fox]]es, though previously thought to be almost as reliant on lemmings, seem to be more loosely coupled and more generalized and did not decline as much).<ref name= Schmidt>{{cite journal|pmid=22977153}}</ref><ref>{{cite journal|doi=10.4080/gpcw.2011.0113}}</ref> The amount of lemming mounds is much less than it once in northern Greenland and any variety of [[population cycle]] has been apparently abandoned by what remains of the lemmings.<ref name= Schmidt/>
[[Global warming|Climate change]] is now widely perceived to perhaps the primary driver of the snowy owl's decline. As temperatures continue to rise, abiotic factors such as increased rain and reduced snow are likely to effect lemming populations and, in turn, snowy owls. These and potentially many other issues (possibly including modifying migrating behavior, vegetation composition, increased insect, disease and parasite activities, risk of [[hyperthermia]]) are a matter of concern.<ref name="iucn status 19 November 2021" /><ref name= Holt/><ref name= Heggoy/><ref>Inouye, D. W. (2019). "Climate change in other taxa". ''Effects of Climate Change on Birds'', p. 257. {{ISBN|9780198824268}}</ref> Additionally, reduction of sea ice, which snowy owls are now known to rely extensively on, as a result of warming climates, impacts could be significant.<ref name="iucn status 19 November 2021" /><ref name= Holt/><ref name= Marine/> The effect of [[climate change]] was essentially confirmed in northern Greenland where a perhaps irrevocable collapse of the lemming population was observed. From 1998 to 2000, the lemming numbers appeared to have quickly declined. The number of lemmings per hectare (ha) is less than one-fifth of what it once was in Greenland (i.e. from 12 lemmings per ha to less than 2 per ha at peak). This is almost certainly correlated with a 98% decline in owl productivity as well as that of the local [[Stoat|stoats]] (the [[long-tailed jaeger]] and [[Arctic fox]]es, though previously thought to be almost as reliant on lemmings, seem to be more loosely coupled and more generalized and did not decline as much).<ref name= Schmidt>{{cite journal|pmid=22977153}}</ref><ref>{{cite journal|doi=10.4080/gpcw.2011.0113}}</ref> The amount of lemming mounds is much less than it once in northern Greenland and any variety of [[population cycle]] has been apparently abandoned by what remains of the lemmings.<ref name= Schmidt/>


==In popular culture==
==In popular culture==

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'wikitext'
Old page wikitext, before the edit (old_wikitext)
'{{Short description|Species of owl}} {{Redirect|Arctic owl|the racehorse|Arctic Owl (horse)}} {{pp-protected|small=yes}} {{Speciesbox | name = Snowy owl | fossil_range= {{Fossil range|Pleistocene|Present}}<ref>{{cite web |title=Bubo scandiacus Linnaeus 1758 (snowy owl) |url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=368622&is_real_user=1 |website=PBDB}}</ref> | status = VU | status_system = IUCN3.1 | status_ref =<ref name="iucn status 19 November 2021">{{cite iucn |author=BirdLife International |date=2020 |title=''Bubo scandiacus'' |volume=2020 |page=e.T22689055A181375387 |doi=10.2305/IUCN.UK.2020-3.RLTS.T22689055A181375387.en |access-date=19 November 2021}}</ref> | image = Snowy Owl (240866707).jpeg | range_map = Cypron-Range Bubo scandiacus.svg | range_map_caption = <br />{{legend0|#0C5F8E|Breeding|border=solid 1px cecece}} {{legend0|#59B1D8|Non Breeding|border=solid 1px cecece}} | genus = Bubo | species = scandiacus | authority = ([[Carl Linnaeus|Linnaeus]], [[10th edition of Systema Naturae|1758]]) | synonyms = *''Strix scandiaca'' {{small|Linnaeus,&nbsp;1758}} *''Strix nyctea'' {{small|Linnaeus,&nbsp;1758}} *''Nyctea scandiaca'' <small>(Linnaeus,&nbsp;1758)</small> }} {{Use dmy dates|date=June 2020}} The '''snowy owl''' (''Bubo scandiacus''), also known as the '''polar owl''', the '''white owl''' and the '''Arctic owl''',<ref name= Potapov>{{cite book|title=The Snowy Owl|author1=Potapov, Eugene |author2=Sale, Richard |name-list-style=amp |publisher = T&APoyser|year = 2013| isbn = 978-0713688177}}</ref> is a large, white [[owl]] of the [[true owl]] family.<ref name= Konig>{{cite book |last=König |first=Claus |title=Owls of the World |year=2008 |publisher=Christopher Helm |location=London |isbn=9781408108840 |edition=2nd |author2=Weick, Friedhelm }}</ref> Snowy owls are native to the [[Arctic]] regions of both North America and the [[Palearctic]], breeding mostly on the [[tundra]].<ref name="iucn status 19 November 2021" /> It has a number of unique adaptations to its habitat and lifestyle, which are quite distinct from other extant owls.<ref name= Voous>{{cite book | last =Voous | first = Karel H. | author-link = Karel H. Voous |author2 = Cameron, Ad (illustrator) |title = Owls of the Northern Hemisphere| year = 1988 | publisher = London, Collins | isbn =978-0-00-219493-8|pages =209–219}}</ref> One of the largest species of owl, it is the only owl with largely white plumage.<ref name= Konig/> Males tend to be a purer white overall while females tend to more have more extensive flecks of dark brown.<ref name= Holt>Holt, D. W., M. D. Larson, N. Smith, D. L. Evans, and D. F. Parmelee (2020). [https://birdsoftheworld.org/bow/species/snoowl1/cur/introduction Snowy Owl (''Bubo scandiacus'')], version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.</ref> Juvenile male snowy owls have dark markings that may appear similar to females until maturity, at which point they typically turn whiter. The composition of brown markings about the wing, although not foolproof, is the most reliable technique to age and sex individual snowy owls.<ref name= Solheim>{{cite journal|author=Solheim, R.|title=Wing feather moult and age determination of Snowy Owls ''Bubo scandiacus''|doi=10.15845/on.v35i0.289|url=https://boap.uib.no/index.php/ornis/article/view/289}}</ref> Most owls sleep during the day and [[Nocturnality|hunt at night]], but the snowy owl is often active during the day, especially in the summertime.<ref name= Voous/> The snowy owl is both a specialized and generalist hunter. Its breeding efforts and entirely global population are closely tied to the availability of tundra-dwelling [[lemming]]s but in the non-breeding season and occasionally during breeding the snowy owl can adapt to almost any available prey, most often other small [[mammal]]s and northerly [[water bird]]s (as well as, opportunistically, [[carrion]]).<ref name= Potapov/><ref name= Holt/> Snowy owls typically nest on a small rise on the ground of the tundra.<ref name= Hume>Hume, R. (1991). ''Owls of the world''. Running Press, Philadelphia.</ref> The snowy owl lays a very large clutch of [[egg]]s, often from about 5 to 11, with the laying and hatching of eggs considerably staggered.<ref name= Holt/> Despite the short [[Climate of the Arctic|Arctic summer]], the development of the young takes a relatively long time and independence is sought in autumn.<ref name= Voous/> The snowy owl is a nomadic bird, rarely breeding at the same locations or with the same mates on an annual basis and often not breeding at all if prey is unavailable.<ref name= Holt/> A largely [[Bird migration|migratory bird]], snowy owls can wander almost anywhere close to the Arctic, sometimes unpredictably [[Animal migration|irrupting]] to the south in large numbers.<ref name= Holt/><ref name= Sindelar>{{cite journal|author=Sindelar Jr., C. |url=https://search.library.wisc.edu/digital/AXWMS2WTWUPCLO8G/pages/AX2FPHBQQK72DD8I|year=1966|title=A comparison of five consecutive Snowy Owl invasions in Wisconsin|journal= Passenger Pigeon|volume= 28|issue=10|pages= 108}}</ref> Given the difficulty of surveying such an unpredictable bird, there was little in depth knowledge historically about the snowy owl's status. However, recent data suggests the species is declining precipitously.<ref name="iucn status 19 November 2021" /><ref name= Bent>Bent, A. C. (1938). ''Life Histories of North American Birds of Prey (part 2), Orders Falconiformes and Stringiformes (Vol. 170)''. US Government Printing Office.</ref> Whereas the global population was once estimated at over 200,000 individuals, recent data suggests that there are probably fewer than 100,000 individuals globally and that the number of successful breeding pairs is 28,000 or even considerably less.<ref name="iucn status 19 November 2021" /><ref name= Marthinsen>{{cite journal|doi=10.1007/s10592-008-9581-6|title=No phylogeographic structure in the circumpolar snowy owl (''Bubo scandiacus'')|url=https://www.researchgate.net/publication/226518592_No_phylogeographic_structure_in_the_circumpolar_Snowy_Owl_Bubo_scandiacus}}</ref> While the causes are not well-understood, numerous, complex environment factors often correlated with [[global warming]] are probably at the forefront of the fragility of the snowy owl's existence.<ref name="iucn status 19 November 2021" /><ref name= Holt/> == Taxonomy == The snowy owl was one of the many [[Aves in the 10th edition of Systema Naturae|bird species originally described]] by [[Carl Linnaeus]] in his landmark 1758 [[10th edition of Systema Naturae|10th edition of ''Systema Naturae'']], where it was given the binomial name ''Strix scandiaca''.<ref>{{cite book | last= Linnaeus | first =Carl | author-link=Carl Linnaeus | title=Systema Naturae per Regna Tria Naturae, Secundum Classes, Ordines, Genera, Species, cum Characteribus, Differentiis, Synonymis, Locis. Tomus I. Editio decima, reformata | publisher= (Laurentii Salvii)|location=[[Stockholm|Holmiae]] | language = la | year=1758| page= 92 | url=https://archive.org/stream/carolilinnaeisy00gesegoog#page/n102/mode/1up}}</ref> The genus name ''Bubo'' is [[Latin]] for an [[horned owl]] and ''scandiacus'' is [[New Latin]] for of [[Scandinavia]].<ref name=job>{{cite book | last= Jobling | first= James A | year= 2010| title= The Helm Dictionary of Scientific Bird Names| url= https://archive.org/details/Helm_Dictionary_of_Scientific_Bird_Names_by_James_A._Jobling/page/n179 | publisher= Christopher Helm | location = London | isbn = 978-1-4081-2501-4 | pages = 179, 349}}</ref> The former genera name ''Nyctea'' is derivation of Greek meaning "night".<ref name= Potapov/> Linnaeus originally described the different plumages of this owl as separate species, with the male specimens of snowy owls being considered ''Strix scandiaca'' and the likely females considered as ''Strix nyctea''.<ref name= Potapov/><ref>{{cite journal|author=Lönnberg, E. |title=Olof Rudbeck, Jr., the first Swedish Ornithologist|journal=Ibis|year=2008|volume=73|issue=2|pages=302–307|doi=10.1111/j.1474-919X.1931.tb01519.x}}</ref> Until recently, the snowy owl was regarded as the sole member of a distinct [[genus]], as ''Nyctea scandiaca'', but [[Mitochondrial DNA|mtDNA]] [[cytochrome b|cytochrome ''b'']] [[Nucleic acid sequence|sequence]] data shows that it is very closely related to the [[horned owl]]s in the genus ''Bubo'' and the species is now thusly often considered inclusive with that genus.<ref name= Wink>Wink, M. & Heidrich, P. (2000). "Molecular systematics of owls (Strigiformes) based on DNA-sequences of the mitochondrial cytochrome b gene", pp. 819–828 in: Chancellor, R.D. & Meyburg, B.U. eds. (2000). ''Raptors at Risk. Proceedings of the V World Conference on Birds of Prey and Owls''. Midrand, Johannesburg, 4–11 August 1998. WWGBP & Hancock House, Berlin & Blaine, Washington.</ref><ref>Penhallurick, J. M. (2002). "The taxonomy and conservation status of the owls of the world: a review". ''Ecology and conservation of owls''. CSIRO, Collingwood, pp. 343–354.</ref> However, some authorities debate this classification, still preferring ''Nyctea''. Often authorities are motivated to retain the separate genus on the grounds of [[Osteology|osteological distinctions]].<ref name= Potapov/><ref name= Ford>Ford, N. L. (1967). ''A systematic study of the owls based on comparative osteology''. PhD diss, Univ. of Michigan, Ann Arbor.</ref> [[File:121 Snowy Owl.jpg|thumb|left|The engraving ''[[Snowy Owl (Audubon)|Snowy Owl]]'', Plate 121 of ''[[The Birds of America]]'' by [[John James Audubon]]. Male (top) and female (bottom).]] Genetic testing revealed a reasonably distinct genetic makeup for snowy owls, being about 8% genetically distinct from other ''Bubo'' owls, perhaps giving credence to those who count the species as separate under ''Nyctea''.<ref name= Potapov/><ref>{{cite journal|pmid=14997323|year=2004|last1=Yamada|first1=K.|last2=Nishida-Umehara|first2=C.|last3=Matsuda|first3=Y.|title=A new family of satellite DNA sequences as a major component of centromeric heterochromatin in owls (Strigiformes)|journal=Chromosoma|volume=112|issue=6|pages=277–287|doi=10.1007/s00412-003-0267-z|s2cid=7848355}}</ref> However, a fairly recent shared origin in evolutionary history has been illustrated through a combination of genetic study and fossil review and there is little, other than osteology of the [[tarsometatarsus]], to outright distinguish the snowy owl from other modern species like the [[Eurasian eagle-owl]] (''Bubo bubo'').<ref name= Potapov/><ref name= Voous/> Genetic testing has indicated that the snowy owl may have diverged from related species at around 4 million years ago.<ref name= Potapov/> Furthermore, it has determined that the living species genetically most closely related to the snowy owl is the [[great horned owl]] (''Bubo virginianus'').<ref name= Potapov/><ref name= Wink2>{{cite journal|doi=10.5253/078.097.0425|title=Molecular Phylogeny of Owls (Strigiformes) Inferred from DNA Sequences of the Mitochondrial Cytochromeband the Nuclear ''RAG-1'' gene|year=2009|last1=Wink|first1=Michael|last2=El-Sayed|first2=Abdel-Aziz|last3=Sauer-Gürth|first3=Hedi|last4=Gonzalez|first4=Javier|journal=Ardea|volume=97|issue=4|pages=581–591|s2cid=55406064}}</ref> On a broader scale, owls in general have, through genetic materials, been determined to be a highly distinct group, with outwardly similar groups such as [[Caprimulgiformes]] revealed to not be at all closely related.<ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/auk/v098n04/p0681-p0714.pdf|author=Cracraft, J.|title=Toward a Phylogenetic Classification of the Recent Birds of the World (Class Aves) |doi=10.1093/auk/98.4.681|doi-broken-date=2021-11-30|journal=The Auk|volume= 98|issue= 4|year= 1981|pages =681–714 }}</ref><ref>{{cite book|doi=10.1016/B978-012498315-1/50014-5|author=Mindell, D. P. |year=1997|chapter=Phylogentic relationships among and within select avian orders based on mitochondrial DNA|title=Avian molecular evolution and systematics|pages= 211–247|publisher= Academic Press|isbn=9780124983151 }}</ref> Within the owl order, [[True owl|typical owls]] are highly divergent from [[barn-owl]]s.<ref name= Konig/><ref name= Wink2/> Furthermore, the ''Bubo'' genus likely clustered at some point during the evolutionary process with other largish owls, such as ''[[Strix (genus)|Strix]]'', ''[[Pulsatrix]]'' and ''[[Ciccaba]]'', based on broad similarities in their voice, reproductive behaviors (i.e. hooting postures) and a similar number and structure of [[chromosome]]s and [[autosome]]s.<ref name= Konig/><ref>{{cite journal|doi=10.1007/BF00056765|title=A karyological study of 55 species of birds, including karyotypes of 39 species new to cytology|year=1984|last1=Belterman|first1=R. H. R.|last2=De Boer|first2=L. E. M.|journal=Genetica|volume=65|pages=39–82|s2cid=37933718}}</ref> A number, but not all, of extant typical owls seem to have evolved from an ancient shared [[common ancestor]] with the ''Bubo'' owls.<ref name= Schmutz>{{cite journal|doi=10.1139/g91-110|title=A cytogenetic comparison of some North American owl species|year=1991|last1=Schmutz|first1=Sheila M.|last2=Moker|first2=Jane S.|journal=Genome|volume=34|issue=5|pages=714–717}}</ref> In addition to the question of relationship of the traditional ''Bubo'' owls to the snowy owls, ongoing ambiguity of the relationship of other similarly large-sized owls has been persistent. These have sometimes either been included in the genus or within separate genera, i.e. the ''[[Fish owl|Ketupu]]'' or fish owls and the ''[[Fishing owl|Scotopelia]]'' or fishing owls. Despite the adaptive distinctions, the grouping of these large owls (i.e. ''Bubo'', snowy, fish and perhaps fishing owls) appears to be borne out via research of [[karyotype]]s.<ref name= Konig/><ref name= Schmutz/><ref name= Wink2/><ref name= Mikkola>''Owls of the World: A Photographic Guide'' by Mikkola, H. Firefly Books (2012), {{ISBN|9781770851368}}</ref><ref>{{cite journal|doi=10.1071/MU02006|url=https://www.researchgate.net/publication/248900150|title=A new Ninox owl from Sumba, Indonesia|year=2002|last1=Olsen|first1=Jerry|last2=Wink|first2=Michael|last3=Sauer-Gürth|first3=Hedi|last4=Trost|first4=Susan|journal=Emu - Austral Ornithology|volume=102|issue=3|pages=223–231|s2cid=86526031}}</ref> The [[fossil]] history of snowy owls is fairly well documented despite some early confusion on how to distinguish the skeletal structure of the snowy owls from eagle-owls.<ref name= Brodkorb>{{cite journal|url=https://ufdc.ufl.edu/UF00001516/00001|author=Brodkorb, P. |year=1971|title=Catalogue of fossil birds, Part 4 (Columbiformes through Piciformes)|journal= Bulletin of the Florida State Museum, Biological Sciences |volume=15|issue=4|page=163}}</ref><ref>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V100/V100_N08/V100_N8_28_33.pdf|author=Stewart, J. R. |year=2007|title=The fossil and archaeological record of the Eagle Owl in Britain|journal= British Birds|volume= 100|issue=8|pages= 481}}</ref> It was determined that the snowy owl once was distributed much more widely and far farther to the south during the [[Quaternary glaciation]] when much of the [[Northern Hemisphere]] was in the midst of an [[ice age]].<ref name= Potapov/> Fossil records shows that snowy owls once could be found in Austria, Azerbaijan, [[Czechoslovakia]], England, France, Germany, Hungary, Italy, Poland, Sardinia and Spain as well as in the Americas in [[Cape Prince of Wales]], [[Little Kiska Island]], [[St. Lawrence Island]], and in [[Illinois]].<ref name= Holt/><ref name= Brodkorb/> In the [[Late Pleistocene]] the range expanded southward even more so to Bulgaria (80,000–16,000 years, [[Kozarnika]] Cave, W Bulgaria).<ref>{{cite journal|author=Boev, Z.|year= 1998|title= First fossil record of the Snowy Owl ''Nyctea scandiaca'' (Linnaeus, 1758) (Aves: Strigidae) from Bulgaria|url=https://www.researchgate.net/publication/301215428|journal=Historia Naturalis Bulgarica|volume= 9|pages= 79–86}}</ref> and much of the Italian Peninsula.<ref>{{Cite book|author1=Bedetti, C. |author2=Palombo, M.R. |author3=Sardella, R. |date= October 2001|title=1st International Congress "The World of Elephants"|chapter=Last occurrences of large mammals and birds in the Late Quaternary of the Italian peninsula|chapter-url=https://iris.uniroma1.it/handle/11573/253607|pages=701–703|isbn=978-88-8080-025-5}}</ref> [[Pleistocene]] era fossil from France, i.e. ''B. s. gallica'', showed that the snowy owls of the time were somewhat bulkier (though still notably smaller than [[Eurasian eagle-owl|contemporary eagle-owls]] of the times, which were larger than the eagle-owls of today) and ostelogically more sexually dimorphic in size than the modern form (9.9% dimorphism in favor of females in the fossils against 4.8% in the same features today).<ref>Andrews, P. (1990). ''Owls, caves and fossils''. Chicago: University of Chicago Press.</ref> There are no subspecific or other geographical variations reported in the modern snowy owls, with individuals of vastly different origins breeding together readily due to their nomadic habits.<ref name= Holt/> Despite apparent variations in body size, environment conditions are the likely variant rather than genetics.<ref name= Potapov/> No evidence could be found of [[Phylogeography|phylogeographic variation]] could be found in snowy owls upon testing. Furthermore, the snowy owl appears to have a similar level of [[genetic diversity]] as other European owls.<ref name= Marthinsen/><ref>Marthinsen, G., Wennerberg, L., Solheim, R., & Lifjeld, J. T. (2009). Snowy owls (''Bubo scandiacus'') constitute one panmictic population. University of Oslo.</ref> ===Hybrids=== Snowy owls are not known to interbreed with other owl species in the wild, and accordingly, no hybrids of snowy owls and other owl species have yet been sighted in the wild. However, a hobby falconer in [[Kollnburg]], Germany, bred [[Hybrid (biology)|hybrids]] from a male snowy owl and a female Eurasian eagle-owl (''Bubo bubo'') in 2013.<ref>[http://www.tz.de/bayern/ueberraschende-kreuzung-tierreich-schnuhu-mischung-schneeeule-eule-3069906.html "Schnuhu": Überraschende Kreuzung – Ich bin Bayerns süßester Fratz!]. tz.de Retrieved on 7 October 2016</ref> The two resulting male hybrid owls possessed the prominent ear tufts (generally absent in snowy owls), general size, orange eyes, and the same pattern of black markings on their plumage from their Eurasian eagle-owl mother, while retaining the generally black-and-white plumage colours from their snowy owl father. The hybrids were dubbed "''Schnuhus''" from the German words for snowy owl and Eurasian eagle-owl (''Schnee-Eule'' and ''Uhu'', respectively). As of 2014, the hybrids had grown to maturity and were healthy.{{cn|date=March 2021}} == Description == [[File:Bubo scandiacus (Linnaeus, 1758) Male.jpg|thumb|left|A captive adult male.]] The snowy owl is mostly white. They are purer white than predatory mammals like [[polar bear]]s (''Ursus maritimus'') and [[Arctic fox]] (''Vulpes lagopus'').<ref name= Hume/> Often when seen in the field, these owls can resemble a pale rock or a lump of snow on the ground.<ref name= Hume/> It usually appears to lack ear tufts but very short (and probably vestigial) [[Ear tuft|tufts]] can be erected in some situations, perhaps most frequently by the female when she is sitting on the nest.<ref name= Konig/> The ear tufts measure about {{convert|20|to|25|mm|in|abbr=on}} and consist of about 10 small feathers.<ref name= Voous/> The snowy owl has bright yellow eyes.<ref name= Holt/> The head is relatively small and, even for the relatively simply adapted hearing mechanism of a ''Bubo'' owl, the [[facial disc]] is shallow and the ear is uncomplicated.<ref name= Konig/><ref name= Voous/> 1 male had ear slits of merely {{convert|21|x|14|mm|in|abbr=on}} on left and {{convert|21|x|14.5|mm|in|abbr=on}} on the right.<ref name= Voous/> Females are almost invariably more duskily patterned than like-age males.<ref name= Konig/><ref name= Holt/> In mature males, the upper parts are plain white with usually a few dark spots on the miniature ear-tufts, about the head and the tips of some [[Flight feather|primaries and secondaries]] whilst the underside is often pure white.<ref name= Konig/> Despite their reputation for being purely white, only 3 out of 129 Russian museum specimens of adult males showed an almost complete absence of darker spots. The adult female is usually considerably more spotted and often slightly barred with dark brown on the crown and the underparts. Her flight and tail feathers are faintly barred brown while the underparts are white in base color with brown spotting and barring on the flanks and upper breast.<ref name= Konig/> In confusingly plumaged snowy owls, the sex can be determined by the shape of wing markings, which manifest as bars more so in females and spots in males.<ref name= Potapov/><ref name= Lind>{{cite journal|url=https://journals.lub.lu.se/os/article/view/23039|volume=3|year=1993|author=Lind, H. |title=Different ecology in male and female wintering Snowy Owls ''Nyctea scandiaca'' L. in Sweden due to colour and size dimorphism}}</ref> However, the very darkest males and the lightest females are nearly indistinguishable by plumage.<ref name= Potapov/> On rare occasion, a female can appear almost pure white, as has been recorded in both the field and in captivity.<ref name= McMorris>McMorris, A. (2011). ''Snowy Owls: Age, Sex and Plumage''. Presentation Delaware Valley Ornithological Club.</ref> There is some evidence that some of the species grow paler with age after maturity.<ref name= Holt/><ref name= Dementiev>Dementiev, G. P., Gladkov, N. A., Ptushenko, E. S., Spangenberg, E. P., & Sudilovskaya, A. M. (1966). ''Birds of the Soviet Union, vol. 1''. Israel Program for Scientific Translations, Jerusalem.</ref> One study's conclusions were that males were usually but not always lighter and that correctly aging is extremely difficult, sometimes individuals either get lighter, darker or do not change their appearance with age.<ref name= McMorris/> On the other hand, with close study, it is possible to visually identify even individual snowy owls using the pattern of markings on the wing, which can be somewhat unique in each individual.<ref>{{cite journal|title=Identifying Individual Great Gray Owls (''Strix nebulosa'') and Snowy Owls (''Bubo scandiacus'') Using Wing Feather Bar Patterns|url=https://www.researchgate.net/publication/311484678_Identifying_Individual_Great_Gray_Owls_Strix_nebulosa_and_Snowy_Owls_Bubo_scandiacus_Using_Wing_Feather_Bar_Patterns|doi=10.3356/JRR-15-64.1| last=Solheim | first=Roar| volume=50 | issue=4 | year=2016| pages=370–378}}</ref> After a [[Moulting|fresh moult]], some adult females that previously appeared relatively pale newly evidenced dark, heavy markings. On the contrary, some banded individuals over at least four years were observed to have been almost entirely unchanged in the extent of their markings.<ref name= Potapov/><ref name= Holt/> In another very pale owl, the [[barn owl]] (''Tyto alba''), the sexual dimorphism of spotting appears to be driven by genetics while, in snowy owls, environment may be the dictating factor instead.<ref name= Potapov/><ref>{{cite journal|title=Genetic, environmental, and condition‐dependent effects on female and male ornamentation in the barn owl ''Tyto alba''|pmid=28565392| last=Roulin | first=Alexandre | last2=Richner | first2=Heinz | last3=Ducrest | first3=Anne-Lyse| journal=Evolution| volume=52 | issue=5 | year=1998| pages=1451–1460}}</ref> [[File:Snowy Owl - Schnee-Eule.jpg|thumb|right|A captive adult female.]] The chicks are initially grayish white but quickly transition to dark gray-brown in the mesoptile plumage. This type of plumage [[camouflage]]s effectively against the variously colored [[lichen]]s that dot the tundra ground.<ref name= Konig/><ref name= Holt/> This is gradually replaced by plumage showing dark barring on white. At the point of fledging, the plumage often becomes irregularly mottled or blotched with dark and is mostly solidly dark gray-brown above with white eyebrows and other areas of the face white.<ref name= Konig/> Recently fledged young can already be sexed to a semi-reliable degree by the dark marking patterns about their wings.<ref name= Seidensticker>{{cite journal|doi=10.3356/JRR-11-02.1| last=Seidensticker | first=Mathew T. | last2=Holt | first2=Denver W. | last3=Detienne | first3=Jennifer | last4=Talbot | first4=Sandra | last5=Gray | first5=Kathy | title=Sexing Young Snowy Owls | journal=Journal of Raptor Research| volume=45 | issue=4 | year=2011| pages=281–289}}</ref> The juvenile plumage resembles that of adult females but averages slightly darker on average.<ref name= Holt/> By their second [[Moulting|moult]] fewer or more broken bars are usually evidenced on the wing. The extent of white and composition of wing patterns become more dimorphic by sex with each juvenile moult, culminating in the 4th or 5th pre-basic moult, wherein the owls are hard to distinguish from mature adults.<ref name= Potapov/><ref name= Holt/><ref name= Solheim/><ref name= Seidensticker/><ref>{{cite journal|author=Pyle, P.|title=Flight-feather molt patterns and age in North American owls|doi=10.2307/4089230|url=https://www.birdpop.org/docs/pubs/Pyle_1997_Flight_Feather_Molt_Patterns_and_Age_in_NA_Owls.pdf| pages=553| volume=115 | issue=2 | year=1998}}</ref> Moults usually occur from July and September, non-breeding birds moulting later and more extensively, and are never extensive enough to render the owls flightless.<ref name= Potapov/> Evidence indicates that snowy owls may attain adult plumage at 3 to 4 years of age, but fragmentary information suggests that some males are not fully mature and/or as fully white in plumage that they can attain until the 9th or 10th year.<ref name= Holt/><ref name= Seidensticker/><ref name= Cramp>{{cite book |last1=Cramp |first1=S. |last2=Simmons |first2=K.E.L. |year=1985 |title=Birds of the Western Palearctic |volume=Vol. 2 |publisher=Oxford University Press |location=Oxford}}</ref> Generally speaking, moults of snowy owls occur more quickly than do those of Eurasian eagle-owls.<ref name= Solheim/> The toes of the snowy owl are extremely thickly feathered white, while the claws are black.<ref name= Konig/> The toe feathers are the longest known of any owl, averaging at {{convert|33.3|mm|in|abbr=on}}, against the great horned owl which has the 2nd longest toe feathers at a mean of {{convert|13|mm|in|abbr=on}}<ref name= Voous/><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/condor/v083n04/p0302-p0309.pdf|author=Barrows, C. W. |year=1981|title=Roost selection by spotted owls: an adaptation to heat stress|journal= Condor|volume= 83|issue=4|pages= 302–309}}</ref> Occasionally, snowy owls may show a faint blackish edge to the eyes and have a dark gray cere, though this is often not visible from the feather coverage, and a black bill.<ref name= Konig/> Unlike many other whitish birds, the snowy owl does not possess black wingtips, which is theorized to minimize wear-and-tear on the wing feathers in the other whitish bird types.<ref>{{cite journal|doi=10.2307/1362901| last=Averill | first=Charles K. | title=Black Wing Tips | journal=The Condor| volume=25 | issue=2 | year=1923| pages=57–59|jstor=1362901|url=https://sora.unm.edu/sites/default/files/journals/condor/v025n02/p0057-p0059.pdf}}</ref> The conspicuously notched primaries of the snowy owl appear to give an advantage over similar owls in long-distance flight and more extensive flapping flight.<ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/condor/v029n01/p0017-p0018.pdf|title=Emargination of the Long Primaries in Relation to Power of Flight and Migration with One Illustration| volume=29 | issue=1 | year=1927| pages=17–18| last=Averill | first=C. K.| journal=The Condor|doi=10.2307/1363004}}</ref> The snowy owl does have some of the noise-canceling serrations and comb-like wing feathers that render the flight of most owls functionally silent, but they have fewer than most related ''Bubo'' owls. Therefore, in combination with its less soft feathers, the flight of a snowy owl can be somewhat audible at close range.<ref name= Potapov/><ref>{{cite journal|pmid=28163870| last=Wagner | first=Hermann | last2=Weger | first2=Matthias | last3=Klaas | first3=Michael | last4=Schröder | first4=Wolfgang | title=Features of owl wings that promote silent flight | journal=Interface Focus | volume=7 | issue=1 | date=2017| doi=10.1098/rsfs.2016.0078 | page=20160078}}</ref> The flight of snowy owls tends to be steady and direct and is reminiscent to some of the flight of a large, slow-flying falcon.<ref name= Potapov/> Though capable of occasional [[Flying and gliding animals|gliding flight]], there is no evidence that snowy owls will [[Bird flight|soar]]. It is said that the species seldom exceeds a flying height of around {{convert|150|m|ft|abbr=on}} even during passage.<ref name= Potapov/> While the feet are sometimes described as "enormous", the [[Tibiotarsus|tarsus]] is in osteological terms relatively short at 68% the length of those of a Eurasian eagle-owl but the claws are nearly as large, at 89% of the size of those of the eagle-owl.<ref name= Voous/><ref name= Hume/><ref name= Ford/> Despite its relatively short length, the tarsus is of similar circumference as in other ''Bubo'' owls.<ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/jfo/v013n01/p0009-p0012.pdf|author1=Stabler, R. M.|author2 =Hoy, N. D. |year=1942|title=Measurements of Tarsal Circumferences from Living Raptorial Birds|journal= Bird-Banding|pages= 9–12|volume=13|issue=1}}</ref> Also compared to an eagle-owl, the snowy owl has a relatively short decurved [[Rostrum (anatomy)|rostrum]], a proportionately greater length to the [[Interorbital region|interorbital roof]] and a much longer [[sclerotic ring]] surrounding the eyes while the anterior opening are the greatest known in any owl.<ref name= Voous/><ref name= Ford/><ref>{{cite journal|pmid=16717442| last=Iwaniuk | first=Andrew N. | last2=Hurd | first2=Peter L. | last3=Wylie | first3=Douglas R.W. | title=Comparative Morphology of the Avian Cerebellum: I. Degree of Foliation | journal=Brain, Behavior and Evolution| volume=68 | issue=1 | year=2006 | doi=10.1159/000093530 | pages=45–62}}</ref> Owls have extremely large eyes which are nearly the same size in large species such as the snowy owl as those of humans.<ref>Gill, F. (2007). ''Ornithology''. 3rd Edn. (W. H. Freeman Co: New York.</ref> The snowy owl's eye, at about {{convert|23.4|mm|in|abbr=on}} in diameter, is slightly smaller than those of great horned and Eurasian eagle-owls but is slightly larger than those of some other [[Great grey owl|large owls]].<ref name= Voous/><ref>{{cite journal| last=Wills | first=Sarah | last2=Pinard | first2=Chantale | last3=Nykamp | first3=Stephanie | last4=Beaufrère | first4=Hugues| journal=Journal of Zoo and Wildlife Medicine | volume=47 | issue=1 | year=2016 | doi=10.1638/2015-0009.1 | pages=244–255|title=Ophthalmic reference values and lesions in two captive populations of northern owls: great grey owls (''Strix nebulosa'') and snowy owls (''Bubo scandiacus'')}}</ref> Snowy owls must be able to see from great distances and in highly variable conditions but probably possess less acute night vision than many other owls.<ref name= Potapov/> Based on the study of [[dioptre]]s in different owl species, the snowy owl was determined to have eyesight better suited to long-range perception than to close discrimination, while some related species such as great horned owls could probably more successful perceive closer objects.<ref>{{cite journal|doi=10.1007/BF00623904| last=Murphy | first=C. J. | last2=Howland | first2=H. C. | title=Owl eyes: Accommodation, corneal curvature and refractive state | journal=Journal of Comparative Physiology A| volume=151 | issue=3 | year=1983| pages=277–284 }}</ref> Despite their visual limits, snowy owls may have up to 1.5 times more visual acuity than humans.<ref name= Potapov/> Like other owls, snowy owls can probably perceive all colors but cannot perceive [[ultraviolet]] visual pigments.<ref>{{cite journal|pmid=716232| last=Bowmaker | first=J.K. | last2=Martin | first2=G.R. | journal=Vision Research| volume=18 | issue=9 | year=1978 | doi=10.1016/0042-6989(78)90095-0 | pages=1125–1130|title=Visual pigments and colour vision in a nocturnal bird, ''Strix aluco'' (tawny owl)}}</ref><ref>{{cite journal|pmid=4446369|title=Visual acuity in the tawny owl (''Strix aluco'')| doi=10.1016/0042-6989(74)90014-5 | pages=1393–1397| last=Martin | first=Graham R. | last2=Gordon | first2=Ian E. | journal=Vision Research}}</ref><ref>{{cite journal|pmid=24258716| last=Lind | first=Olle | last2=Mitkus | first2=Mindaugas | last3=Olsson | first3=Peter | last4=Kelber | first4=Almut | title=Ultraviolet vision in birds: the importance of transparent eye media | journal=Proceedings of the Royal Society B: Biological Sciences | volume=281 | issue=1774 | date=2014| doi=10.1098/rspb.2013.2209 | page=20132209}}</ref><ref>{{cite journal|doi=10.1007/BF00616750| last=Burkhardt | first=Dietrich | title=UV vision: a bird's eye view of feathers | journal=Journal of Comparative Physiology A| volume=164 | issue=6 | year=1989| pages=787–796}}</ref> Owls have the largest brains of any bird (increasing in sync with the size of the owl species), with the size of the brain and eye related less to [[intelligence]] than perhaps to increased nocturnality and predatory behavior.<ref>{{cite journal|pmid=12028780| last=Garamszegi | first=L. Z. | last2=Møller | first2=A. P. | last3=Erritzøe | first3=J. | title=Coevolving avian eye size and brain size in relation to prey capture and nocturnality | journal=Proceedings of the Royal Society of London. Series B: Biological Sciences | volume=269 | issue=1494 | date=2002| doi=10.1098/rspb.2002.1967 | pages=961–967}}</ref> ===Size=== [[File:Snowy Owl Barrow Alaska.jpg|thumb|left|Young owl on the tundra at [[Utqiaġvik]], Alaska. Snowy owls lose their black feathers with age, although individual females may retain some]] The snowy owl is a very large owl.<ref name= Konig/> They are the largest avian predator of the [[Arctic|High Arctic]] and one of the largest owls in the world.<ref name= Voous/> Snowy owls are about the sixth or seventh heaviest living owl on average, around the fifth longest and perhaps the third longest winged.<ref name= Konig/><ref name= Mikkola/><ref name= Weidensaul>Weidensaul, S. (2015). ''Owls of North America and the Caribbean''. Houghton Mifflin Harcourt.</ref><ref name= CRC>{{cite book |title=CRC Handbook of Avian Body Masses |edition=2nd |editor-first=John B. Jr. |editor-last=Dunning |publisher=CRC Press |year=2008 |isbn=978-1-4200-6444-5}}</ref> This species is the heaviest and longest winged owl (as well as the second longest) in North America, the second heaviest and longest winged owl in Europe (and third longest) but is outsized in bulk by about 3 to 4 other species in Asia.<ref name= Potapov/><ref name= Cramp/><ref name= Weidensaul/><ref>{{cite journal|doi=10.2307/4078421| last=Poole | first=Earl L. | title=Weights and Wing Areas in North American Birds | journal=The Auk| volume=55 | issue=3 | year=1938| pages=511–517}}</ref> Despite being sometimes described as of similar size, the snowy owl is somewhat larger in all aspects of average size than the [[great horned owl]] while the similarly specialized [[taiga]]-dwelling [[great grey owl]] (''Strix nebulosa''), is longer in total length and of similar dimensions in standard measurements, but is shorter winged and much less heavy than the snowy owl.<ref name= Potapov/><ref name= Weidensaul/><ref name= CRC/> In Eurasia, the [[Eurasian eagle-owl]] is larger in all standards of measurements than the snowy owl not to mention two additional species each from Africa and Asia that are slightly to considerably heavier on average than the snowy owl.<ref name= CRC/> Like most [[birds of prey]], the snowy owl shows [[Sexual dimorphism|reverse sexual dimorphism]] relative to most non-raptorial birds in that females are larger than males.<ref name= Potapov/> Sexual dimorphism that favors the female may have some correlation with being able to more effectively withstand food shortages such as during brooding as well as the rigors associated with incubating and brooding.<ref>{{cite journal|doi=10.2307/3676862| last=Lundberg | first=Arne | title=Adaptive Advantages of Reversed Sexual Size Dimorphism in European Owls | journal=Ornis Scandinavica| volume=17 | issue=2 | year=1986 | page=133}}</ref> Females are sometimes described as “giant” whereas males appear relatively “neat and compact”.<ref name= Hume/> However, the sexual dimorphism is relatively less pronounced compared to some other ''Bubo'' species.<ref name= Potapov/><ref name= Weick>{{cite book |title=Owls (Strigiformes): Annotated and Illustrated Checklist |last=Weick |first=Friedhelm |year=2007 |publisher=Springer |isbn=978-3-540-39567-6}}</ref><ref>{{cite journal| last=Korpimaki | first=Erkki | title=Reversed Size Dimorphism in Birds of Prey, Especially in Tengmalm's Owl ''Aegolius funereus'': A Test of the "Starvation Hypothesis" | journal=Ornis Scandinavica | volume=17 | issue=4 | year=1986 | doi=10.2307/3676820 | page=326}}</ref> Male snowy owls have been known to measure from {{convert|52.5|to|64|cm|in|abbr=on}} in total length, with an average from four large samples of {{convert|58.7|cm|in|abbr=on}} and a maximum length, perhaps in need of verification, of reportedly {{convert|70.7|cm|in|abbr=on}}.<ref name= Eckert>Eckert, A. W. (1987). ''The Owls of North America, North of Mexico: All the Species and Subspecies Illustrated in Color and Fully Described''. Gramercy.</ref><ref name= Parmelee>Parmelee, D. F. (1972). ''Canada's incredible arctic owls''. Beaver no. summer:30–41.</ref><ref name= Priklonskiy>Priklonskiy, S.G. (1993). ''Snowy Owl — Nyctea scandiaca (Linnaeus, 1758)''. In: ''Birds of Russia and adjoining regions: Pterocliformes, Columbiformes, Cuculiformes, Strigiformes''. Moscow, p. 258–270. (in Russian).</ref><ref name= Keith>{{cite journal|author=Keith, L.B. |year=1960|title=Observations of Snowy Owls at Delta, Manitoba|journal= Canadian Field-Naturalist|volume= 74|pages=106–112}}</ref> In wingspan, males may range from {{convert|116|to|165.6|cm|ftin|0|abbr=on}}, with a mean of {{convert|146.6|cm|ftin|0|abbr=on}}.<ref name= Dementiev/><ref name= Eckert/><ref name= Priklonskiy/><ref name= Keith/> In females, total length has been known to range from {{convert|54|to|71|cm|in|abbr=on}}, with a mean of {{convert|63.7|cm|in|abbr=on}} and an unverified maximum length of perhaps {{convert|76.7|cm|in|abbr=on}} (if so they would have the second longest maximum length of any living owl, after only the great grey owl).<ref name= Eckert/><ref name= Parmelee/><ref name= Priklonskiy/><ref name= Keith/> Female wingspans have reportedly measured from {{convert|146|to|183|cm|ftin|0|abbr=on}}, with a mean of {{convert|159|cm|ftin|0|abbr=on}}.<ref name= Eckert/><ref name= Priklonskiy/><ref name= Keith/> Despite one study claiming that snowy owl had the highest [[wing loading]] (i.e. grams per square cm of wing area) of any of 15 well-known owl species, more extensive sampling demonstratively illustrated that the wing loading of snowy owls is notably lower than Eurasian eagle- and great horned owls.<ref name= Mikkola/> The conspicuously long-winged profile of a flying snowy owl compared to these related species may cause some to compare their flight profile to a bulkier version of an enormous ''[[Buteo]]'' or a large [[falcon]].<ref name= Potapov/> Body mass in males can average from {{convert|1465|to|1808.3|g|lb|abbr=on}}, with a median of {{convert|1658.2|g|lb|abbr=on}} and a full weight range of {{convert|1300|to|2500|g|lb|abbr=on}} from six sources.<ref name= Konig/><ref name= Dementiev/><ref name= Eckert/><ref name= Priklonskiy/><ref name= Keith/><ref name= Earhart>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/condor/v072n03/p0251-p0264.pdf| last=Earhart | first=Caroline M. | last2=Johnson | first2=Ned K. | title=Size Dimorphism and Food Habits of North American Owls | journal=The Condor| volume=72 | issue=3 | year=1970| pages=251–264|doi=10.2307/1366002}}</ref><ref name= Kerlinger>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/jfo/v059n01/p0007-p0012.pdf|author1=Kerlinger, P.|author2=Lein, M. R. |year=1988|title=Causes of Mortality, Fat Condition, and Weights of Wintering Snowy Owls|journal= Journal of Field Ornithology|volume=59|issue=1|pages= 7–12}}</ref> Body mass in females can average from {{convert|1706.7|to|2426|g|lb|abbr=on}}, with a median of {{convert|2101.8|g|lb|abbr=on}} and a full weight range of {{convert|1330|to|2951|g|lb|abbr=on}}.<ref name= Dementiev/><ref name= Eckert/><ref name= Priklonskiy/><ref name= Keith/><ref name= Earhart/><ref name= Kerlinger/><ref>National Geographic Society. [http://animals.nationalgeographic.com/animals/birds/snowy-owl.html "Snowy Owl"].</ref> Larger than the aforementioned body mass studies, a massive pooled dataset at six wintering sites in North America showed that 995 males averaged at {{convert|1636|g|lb|abbr=on}} while 1,189 females were found to average {{convert|2109|g|lb|abbr=on}}.<ref name= Holt/><ref>{{cite journal|title=Mass growth rates, plumage development, and related behaviors of Snowy Owl (''Bubo scandiacus'') nestlings|doi=10.3356/rapt-50-02-131-143.1| last=Holt | first=Denver W. | last2=Gray | first2=Kathy | last3=Maples | first3=Michael T. | last4=Korte | first4=Mark A. | journal=Journal of Raptor Research| volume=50 | issue=2 | year=2016| pages=131–143}}</ref><ref name= Chang>{{cite journal| last=Chang | first=Alexander M. | last2=Wiebe | first2=Karen L. | journal=The Auk| volume=133 | issue=4 | year=2016| pages=738–746|title=Body condition in Snowy Owls wintering on the prairies is greater in females and older individuals and may contribute to sex-biased mortality|doi=10.1642/AUK-16-60.1|url=https://www.researchgate.net/publication/307548228_Body_condition_in_Snowy_Owls_wintering_on_the_prairies_is_greater_in_females_and_older_individuals_and_may_contribute_to_sex-biased_mortality}}</ref> Reported weights of down to {{convert|710|g|lb|abbr=on}} for males and of {{convert|780|to|1185|g|lb|abbr=on}} for females are probably in reference to owls in a state of [[starvation]].<ref name= Konig/><ref name= Potapov/><ref name= Pitelka>{{cite journal|doi=10.2307/1364693| last=Pitelka | first=Frank A. | last2=Tomich | first2=P. Quentin | last3=Treichel | first3=George W. | title=Breeding Behavior of Jaegers and Owls near Barrow, Alaska | journal=The Condor| volume=57 | issue=1 | year=1955| pages=3–18|url=https://sora.unm.edu/sites/default/files/journals/condor/v057n01/p0003-p0018.pdf}}</ref> Such emaciated individuals are known to highly impaired and starvation deaths are probably not infrequent in winters with poor food accesses.<ref name= Potapov/><ref name= Pitelka/> [[File:The bird, its form and function (1906) (14755679525).jpg|thumb|left|Snowy owls have powerful feet that are heavily covered with feathering.]] Standard measurements have been even more widely reported than length and wingspan.<ref name= Potapov/> The [[Wing chord (biology)|wing chord]] of males can vary from {{convert|351|to|439|mm|in|abbr=on}}, averaging from {{convert|380.1|to|412|mm|in|abbr=on}} with a median of {{convert|402.8|mm|in|abbr=on}}.<ref name= Dementiev/><ref name= Eckert/><ref name= Parmelee/><ref name= Priklonskiy/><ref name= Earhart/><ref name= Josephson>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/jfo/v051n02/p0149-p0160.pdf|author=Josephson, B. |year=1980|title=Aging and sexing snowy owls|journal= Journal of Field Ornithology |volume=51|pages= 149–160}}</ref> The wing chord of females can vary from {{convert|380|to|477.3|mm|in|abbr=on}}, averaging from {{convert|416.2|to|445|mm|in|abbr=on}} with a median of {{convert|435.5|mm|in|abbr=on}}.<ref name= Dementiev/><ref name= Eckert/><ref name= Parmelee/><ref name= Priklonskiy/><ref name= Earhart/><ref name= Josephson/> The [[tail]] length of males can vary on average from {{convert|209.6|to|235.4|mm|in|abbr=on}}, with a full range of {{convert|188|to|261|mm|in|abbr=on}} and a median of {{convert|227|mm|in|abbr=on}}.<ref name= Eckert/><ref name= Parmelee/><ref name= Priklonskiy/><ref name= Keith/><ref name= Josephson/> The tail length of females can average from {{convert|228.5|to|254.4|mm|in|abbr=on}}, with a full range of {{convert|205|to|288|mm|in|abbr=on}} and a median of {{convert|244.4|mm|in|abbr=on}}.<ref name= Eckert/><ref name= Parmelee/><ref name= Priklonskiy/><ref name= Keith/><ref name= Josephson/> Data indicates that slightly longer wing chord and tail lengths were reported on average in Russian data than in American research, however the weights were not significantly different in the two regions.<ref name= Kerlinger/> Less widely taken measurements include the [[Culmen (bird)|culmen]], which can measure from {{convert|24.6|to|29|mm|in|abbr=on}} with a median average of {{convert|26.3|mm|in|abbr=on}} in males and {{convert|27.9|mm|in|abbr=on}} in females, and the [[Beak|total bill]] length which is from {{convert|25|to|42|mm|in|abbr=on}}, with an average in both sexes of {{convert|35.6|mm|in|abbr=on}}.<ref name= Eckert/><ref name= Parmelee/><ref name= Priklonskiy/> [[Tibiotarsus|Tarsal length]] in males averages about {{convert|63.6|mm|in|abbr=on}}, with a range of {{convert|53|to|72|mm|in|abbr=on}}, and averages about {{convert|66|mm|in|abbr=on}}, with a range of {{convert|54|to|75|mm|in|abbr=on}}, in females.<ref name= Parmelee/><ref name= Priklonskiy/> ===Identification=== [[File:Bubo scandiacus male Muskegon.jpg|thumb|right|Male snowy owls such as this are particularly distinctive due to the extensive whiteness.]] The snowy owl is certainly one of the most unmistakable owls (or perhaps even animals) in the world.<ref name= Voous/><ref name= Hume/> No other species attains the signature white stippled sparsely with black-brown color of these birds, a coloring which renders their bright yellow eyes all the more detectable, nor possesses their obvious extremely long feathering.<ref name= Konig/> The only other owl to breed in the [[Arctic|High Arctic]] is the [[short-eared owl]] (''Asio flammeus''). Both species inhabit open country, overlap in range and are often seen by day, but the short-eared is much smaller and more tan or straw-colored in coloration, with streaked brown on chest. Even the palest short-eared owls conspicuously differ and are darker than the snowy owl; additionally the short-eared most often hunts in extended flights.<ref name= Holt/><ref name="Pyle">Pyle, P. (1997). ''Identification Guide to North American Birds, Part I: Columbidae to Ploceidae''. Slate Creek Press, Bolinas, CA, USA.</ref> More similar owls such as the [[Eurasian eagle-owl]] and the [[great horned owl]] attain a fairly pale, sometimes white-washed look in their northernmost races. These species do not normally breed nearly as far north as snowy owls but overlaps certainly do occur when snowy owls when the latter owl sometimes comes south in winter. However, even the most pale great horned and Eurasian eagle-owls are still considerably more heavily marked with darker base colors than snowy owls (the whitest eagle-owls are paler than the whitest great horned owls), possess much larger and more conspicuous [[ear tuft]]s and lack the bicolored appearance of the darkest snowy owls. While the great horned owl has yellow eyes like the snowy owl, the Eurasian eagle-owl tends to have bright orange eyes. The [[open terrain]] habitats normally used by wintering snowy owls are also distinct from the typical [[Woodland edge|edge]] and [[Rock (geology)|rock]]y habitats usually favored by the great horned and Eurasian eagle-owls, respectively.<ref name= Konig/><ref>{{cite book|last=Smith|first=Dwight G.|title=Great Horned Owl|year=2002|publisher=Stackpole Books|location=Mechanicsburg, PA |url=https://books.google.com/books?id=f1PVJVWbQKwC |isbn=978-0811726894 |pages=33; 80–81 |edition=1st }}</ref><ref name="Pyle" /> ===Vocalizations=== The snowy owl differ in their calls from other ''Bubo'' owls, with a much more barking quality to their version of a hooting song.<ref name= Hume/> Perhaps as many as 15 different calls by mature snowy owls have been documented.<ref name= Evans>{{cite journal|url=https://sora.unm.edu/node/112819|author=Evans, D. L. |year=1980|title=Vocalizations and territorial behavior of wintering Snowy Owls|journal=Am. Birds|volume= 34|pages= 748–749}}</ref><ref name= Sutton1>Sutton, G. M. (1932). ''The exploration of Southampton Island. Part II, Zoölogy. Section 2.-The birds of Southampton Island''. Memoirs of the Carnegie Museum 12 (2):1–275.</ref> The main vocalization is a monotonous sequence that normally contains 2–6 (but occasionally more), rough notes similar to the rhythm of a barking dog: ''krooh krooh krooh krooh''...<ref name= Konig/> The call may end with an emphatic ''aaoow'', which is somewhat reminiscent of the deep alarm call of a [[great black-backed gull]] (''Larus marinus'').<ref name= Voous/> They will call mainly from a perch but also sometimes do so in flight.<ref name= Konig/> The ''krooh'' call of the male snowy owl may perform multiple functions such as competitive exclusion of other males and advertising to females.<ref name= Holt/><ref name= Taylor>Taylor, P.S. (1973). ''Breeding behaviour of the Snowy Owl''. Living Bird. 12: 137–154.</ref> The calls of this species may carry exceptionally far in the thin air of Arctic, certainly over more than {{convert|3|km|mi|abbr=on}}, and maybe even to as much {{convert|10|to|11|km|mi|abbr=on}} away.<ref name= Voous/><ref name= Bent/> The female has a similar call to male but can be higher-pitched and/or more guttural as well as single notes which are often disyllabic, ''khuso''.<ref name= Konig/> Female snowy owls have also been known to utter chirps and high screaming notes, similar to those of the nestlings.<ref name= Konig/> Both sexes may at times give a series of clucking, squeals, grunts, hisses and cackles, perhaps such as in circumstances when they are excited.<ref name= Konig/><ref name= Voous/><ref name= Holt/><ref name= Watson>{{cite journal|title=The behaviour, breeding and food-ecology of the Snowy Owl ''Nycea scandiaca''| author=Watson, Adam| year=1957| doi=10.1111/j.1474-919X.1957.tb01959.x| journal=Ibis| volume=99| issue=3| pages =419–462}}</ref> The alarm call is a loud, grating, hoarse ''keeea''.<ref name= Voous/> Another raspier bark is recorded, sometimes called a "watchman's rattle" call, and may be transcribed as ''rick, rick, rick'', ''ha, how, quack, quock'' or ''kre, kre, kre, kre, kre''.<ref name= Sutton/> A female attacking to protect her nest was recorded to let out a crowed ''ca-ca-oh'' call, whilst other owls attacking to protect the nest did a loud version of the typical call while circling before dropping down.<ref name= Taylor/><ref name= Sutton>{{cite journal|doi=10.2307/1364705| last=Sutton | first=George M. | last2=Parmelee | first2=David F. | title=Breeding of the Snowy Owl in Southeastern Baffin Island | journal=The Condor| volume=58 | issue=4 | year=1956 | pages=273–282}}</ref> They may also clap their beak in response to threats or annoyances. While called clapping, it is believed this sound may actually be a clicking of the tongue, not the beak. Though largely only vocal in the breeding season, leading to some erroneous older accounts describing the snowy owl as completely silent, some vocalizations have been recorded in winter in the northern United States.<ref name= Evans/> Initially, the young of the snowy owl have a high pitched and soft begging call which develops into a strong, wheezy scream at around 2 weeks. At the point when the young owls leave the nest around 3 weeks, the shrill squeals they emit may allow the mothers to locate them.<ref name= Parmelee/><ref name= Watson/><ref name= Parmelee2>Parmelee, D. (1992). "Snowy Owl (''Nyctea scandiaca'')". No. 10 in: Poole et al. (1992–1993).</ref> [[File:Juvenile male calling for its mother.jpg|thumb|Juvenile snowy owl, about 12 weeks old]] == Distribution and habitat== ===Breeding range=== The snowy owl is typically found in the northern circumpolar region, where it makes its summer home north of [[60th parallel north|latitude 60° north]] though sometimes down to 55 degrees north.<ref name= Voous/> However, it is a particularly [[nomad]]ic bird, and because population fluctuations in its [[Predation|prey]] species can force it to relocate, it has been known to breed at more southerly latitudes. Although the total breeding range includes a little over {{convert|12000000|km2|sqmi|abbr=on}}, only about {{convert|1300000|km2|sqmi|abbr=on}} have a high probability of breeding, i.e. breeding at no more than 3–9-year intervals.<ref name= Potapov/><ref>{{cite journal|doi=10.1016/j.ecoinf.2014.08.008|title=Discovering and developing primary biodiversity data from social networking sites: A novel approach|year=2014|last1=Barve|first1=Vijay|journal=Ecological Informatics|volume=24|pages=194–199}}</ref> Snowy owls nest in the Arctic [[tundra]] of the northernmost stretches of [[Alaska]], Northern Canada, and [[Palearctic|Eurosiberia]].<ref name= Konig/> [[File:Bobby Tulloch and snowy owl nest site, Fetlar, Shetland, 1967.jpg|thumb|left|[[Bobby Tulloch]], the Shetland [[RSPB]] warden, at the site of the snowy owl nest on the island of [[Fetlar]], Shetland, in August 1967]] Between 1967<ref>{{cite news| title=Snowy Owl with young—an historic photograph | first=Eric | last=Hosking | author-link=Eric Hosking | newspaper=[[The Times]] | location=UK | date=2 August 1967 }}</ref> and 1975, snowy owls bred on the remote island of [[Fetlar]] in the [[Shetland]] Isles north of mainland [[Scotland]], discovered by the Shetland [[RSPB]] warden, [[Bobby Tulloch]].<ref>{{cite news| url=https://www.shetnews.co.uk/2016/11/28/fond-memories-of-the-bobby-the-birdman/ | title=Reviews / Fond memories of the Bobby the birdman | first=Hans J. | last=Marter | newspaper=[[The Shetland News]] | location=UK | date=28 November 2016 | access-date=23 October 2020 }}</ref> Females summered as recently as 1993, but their status in the [[British Isles]] is now that of a rare winter visitor to Shetland, the [[Outer Hebrides]] and the [[Cairngorms]].<ref>[http://news.bbc.co.uk/2/hi/uk_news/scotland/highlands_and_islands/7397993.stm "Hope of first owl chicks in years"], [[BBC News]]. 13 May 2008.</ref><ref>{{cite journal|url=https://www.the-soc.org.uk/files/docs/about-us/publications/scottish-birds/sb-vol15-contents.pdf|author=Marquiss, M., Smith, R. & Galbraith, H. |year=1989|title=Diet of Snowy Owls on Cairn Gorm Plateau in 1980 and 1987|journal= Scottish Birds|volume= 15|issue=4|pages= 180–181}}</ref> Older records show that the snowy owls may have once semi-regularly bred elsewhere in the [[Shetland]]s.<ref>{{cite journal|author=Saxby, H. L. |year=1863|title=Notes on the Snowy Owl|journal= Zoologist |volume=21|pages=8633–8639}}</ref> They range in northern Greenland (mostly [[Peary Land]]) and, rarely in "isolated parts of the highlands", Iceland.<ref name= Konig/><ref name= Voous/><ref name= Potapov/> Thence, they are found breeding at times across northern [[Eurasia]] such as in [[Spitsbergen]] and western and northern [[Scandinavia]]. In Norway, they normally breed in [[Troms og Finnmark]] and seldom down as far south as [[Hardangervidda]] and in Sweden perhaps down to the [[Scandinavian Mountains]] while breeding is very inconsistent in Finland.<ref name= Voous/><ref>Saurola, P. L. (1997). [https://www.fs.usda.gov/treesearch/pubs/15532 ''Monitoring Finnish owls 1982–1996: methods and results'']. United States Department of Agriculture Forest Service General Technical Report NC, pp. 363–380.</ref> They also range in much of northern Russia, including northern [[Siberia]], [[Anadyr Highlands|Anadyr]], [[Koryak Okrug|Koryakland]], [[Taymyr Peninsula]], [[Yugorsky Peninsula]], [[Sakha]] (especially the [[Chukochya River]]) and [[Sakhalin]].<ref name="iucn status 19 November 2021" /><ref name= Konig/><ref name= Voous/> Breeding have also been reported sporadically to the south in the [[Komi Republic]] and even the [[Kama River]] in southern [[Perm Krai]].<ref name= Potapov/> Although considered part of the regular range, the last breeding by snowy owls in the [[Kola Peninsula]] was not since the early 1980s; similarly, breeding maps show the species in [[Arkhangelsk Oblast]] and the [[Pay-Khoy Ridge]] but no breeding records known in at least 30 years in either.<ref>Mineev, O. Y. & Minnev, Y. N. (2005). ''Distribution of owls in North-East European tundra''. In: ''Owls of the Northern Eurasia'' (eds. Volkov S.V., Morozov V.V. & Sharikov A.V.).</ref> They range throughout most of the Arctic [[Island|isles]] of Russia such as [[Novaya Zemlya]], [[Severnaya Zemlya]], [[New Siberian Islands]], [[Wrangel Island]], [[Commander Islands|Commander]] and [[Hall Islands]].<ref name="iucn status 19 November 2021" /><ref name= Konig/><ref name= Voous/> In North America, the breeding range has been known in modern times to include the [[Aleutian islands|Aleutians]] (i.e. [[Buldir Island|Buldir]] and [[Attu Island|Attu]]) and much of northern [[Alaska]], most frequently from the [[Arctic National Wildlife Refuge]] to [[Utqiaġvik, Alaska|Utqiaġvik]], and more sporadically down along the coastal-western parts such as through [[Nome, Alaska|Nome]], [[Hooper Bay, Alaska|Hooper Bay]], the [[Yukon Delta National Wildlife Refuge]], and rarely even south to the [[Shumagin Islands]].<ref name="iucn status 19 November 2021" /><ref name= Voous/> The snowy owl may breed extensively in northern Canada, largely making its home in the [[Arctic Archipelago]].<ref name="iucn status 19 November 2021" /> Their Canadian breeding range can include broadly [[Ellesmere Island]] up to [[Cape Sheridan]], north coastal [[Labrador]], the northern [[Hudson Bay]], perhaps all of [[Nunavut]] (especially the [[Kivalliq Region]]), northeastern [[Manitoba]], both most of northern mainland and insular [[Northwest Territories]] (including the [[River delta|delta]] of the [[Mackenzie River]]) and northern [[Yukon Territory]] (where breeding is mostly confined to [[Herschel Island]]).<ref name="iucn status 19 November 2021" /><ref name= Konig/><ref name= Voous/><ref name= Holt/><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/jrr/v009n03-04/p00060-p00064.pdf|author=Miller, F.L., Russell, R.H. & Gunn, A. |year=1975|title=Distribution and numbers of Snowy Owls on Melville, Eglinton, and Byam Martin Islands, Northwest Territories, Canada|journal=Raptor Research|volume= 9|issue=3–4|pages= 60–64}}</ref> Since breeding and distribution is very small, local and inconsistent in northern Europe, northern Canada and northern Alaska represent the core part of the breeding range for snowy owls along with several parts of northern and northeastern/coastal Russia.<ref name= Potapov/><ref name= Holt/><ref name= Cramp/> ===Regular wintering range=== [[File:Snowy owl Wings 212.jpg|thumb|Wing structure]] During the wintering, many snowy owls leave the dark Arctic to migrate to regions further south. Southern limits of the regular winter range are difficult to delineate given the inconsistency of appearances south of the Arctic.<ref name= Konig/><ref name= Voous/> Furthermore, not infrequently, many snowy owls will overwinter somewhere in the Arctic through the winter, though seldom appear to do so in the same sites where they have bred.<ref name= Potapov/><ref name= Holt/> Due in no small part to the difficulty and hazardousness of observation for biologists during these harsh times, there is very limited data on overwintering snowy owls in the tundra, including how many occur, where they winter and what their ecology is at this season.<ref name= Potapov/><ref name= Holt/> The regular wintering range has at times been thought to include Iceland, Ireland and Scotland and across northern Eurasia such as southern Scandinavia, the [[Baltic islands|Baltics]], central Russia, southwestern [[Siberia]], [[Sakhalin]] southern [[Kamchatka]] and, rarely, north China and sometimes the [[Altai Republic]].<ref name="iucn status 19 November 2021" /><ref name= Konig/><ref name= Holt/><ref name= Cramp/> In North America, they occasionally regularly winter in the Aleutian island chain and do so broadly and with a fair amount of consistency in much of southern Canada, from [[British Columbia]] to [[Labrador]].<ref name= Konig/><ref name= Holt/> Recent research has indicated that snowy owls regularly winter in several of the northern [[Ocean|seas]] during wintertime, following the leads of [[sea ice]] as perching sites and presumably hunting mostly [[seabird]]s in [[polynya]]s.<ref>{{cite journal|doi=10.2307/1366490|jstor=1366490|last1=Irving|first1=Laurence|last2=McRoy|first2=C. Peter|last3=Burns|first3=John J.|title=Birds Observed during a Cruise in the Ice-Covered Bering Sea in March 1968|journal=The Condor|year=1970|volume=72|issue=1|pages=110–112}}</ref><ref>{{cite journal|doi=10.14430/arctic3114|title=Winter Observations of Mammals and Birds, St. Matthew Island|year=1971|last1=McRoy|first1=C. Peter|last2=Stoker|first2=Sam W.|last3=Hall|first3=George E.|last4=Muktoyuk|first4=Edward|journal=Arctic|volume=24}}</ref><ref name= Marine>{{cite journal|doi=10.1111/j.1600-048X.2011.05330.x|title=An avian terrestrial predator of the Arctic relies on the marine ecosystem during winter|year=2011|last1=Therrien|first1=Jean-François|last2=Gauthier|first2=Gilles|last3=Bêty|first3=Joël|journal=Journal of Avian Biology|volume=42|issue=4|pages=363–369}}</ref> In February 1886, a snowy owl landed on the rigging of the [[Nova Scotia]] steamship ''Ulunda'' on the edge of the [[Grand Banks of Newfoundland]], over {{convert|800|km|in|abbr=on}} from the nearest land. It was captured and later preserved at the [[Nova Scotia Museum]].<ref>Conlin, Dan (2 October 2013). [http://marinecurator.blogspot.ca/2013/10/an-owl-oddity.html "An Owl Oddity"], Maritime Museum of the Atlantic.</ref><ref name= Gross1>{{cite journal|doi=10.2307/4080718|jstor=4080718|last1=Gross|first1=Alfred O.|title=Cyclic Invasions of the Snowy Owl and the Migration of 1945-1946|journal=The Auk|year=1947|volume=64|issue=4|pages=584–601}}</ref> Surprisingly, some studies have determined that after a high lemming year in North America, a higher percentage of snowy owls were using marine environments rather than inland ones.<ref>{{cite journal|doi=10.1111/jav.01707|title=Wintering space use and site fidelity in a nomadic species, the snowy owl|year=2018|last1=Robillard|first1=Audrey|last2=Gauthier|first2=Gilles|last3=Therrien|first3=Jean-François|last4=Bêty|first4=Joël|journal=Journal of Avian Biology|volume=49|issue=5}}</ref><ref name= Therrien>{{cite journal|last1=Therrien|first1=Jean-François|title=Winter Use of a Highly Diverse Suite of Habitats by Irruptive Snowy Owls|journal=Northeastern Naturalist|date=March 2017|volume=24|issue=Special Issue 7|pages=B81–B89|doi=10.1656/045.024.s712|s2cid=90013886}}</ref> ===Irruptive range=== Large winter irruptions at temperate latitudes are thought to be due to good breeding conditions resulting in more juvenile migrants.<ref name= Holt/> These result in [[irruptive growth|irruptions]] occurring further south than the typical snowy owl range in some years.<ref name= Santonja>{{cite journal | author1= Santonja, P. |author2= Mestre, I. | author3= Weidensaul, S. | author4= Brinker, D. | author5= Huy, S. |author6= Smith, N. | author7= Mcdonald, T. |author8= Blom, M. | author9= Zazelenchuck, D. |author10= Weber, D. | author11= Gauthier, G. | author12= Lecomte, N. | author13= Therrien, J. |year=2019| title= ''Age composition of winter irruptive Snowy Owls in North America'' | journal=Ibis| volume=161| pages = 211–215| doi= 10.1111/ibi.12647| issue=1| doi-access= free }}</ref> They have been reported, as well as in all northerly states in the contiguous states,<ref>Root, T. R. (1988). ''Atlas of Wintering North American Birds: An Analysis of Christmas Bird Count Data''. University of Chicago Press, Chicago, IL, USA.</ref> as far south as the [[Georgia (U.S. state)|Georgia]], [[Kentucky]], [[South Carolina]], nearly all the [[Gulf Coast of the United States]], [[Colorado]], [[Nevada]], [[Texas]], [[Utah]], California and even Hawaii.<ref name= Voous/><ref name= Bent/><ref>{{cite journal|url=https://www.ksbirds.org/kos/bulletin/Vol64No4.pdf|author1=Robbins, M. B. |author2= Otte, C. |year=2013|title=The irruptive movement of Snowy Owls (''Bubo scandiacus'') into Kansas and Missouri during the winter of 2011–2012|journal= Kansas Ornithological Society Bulletin |volume=64 |issue=4|pages= 41–44}}</ref> In January 2009, a snowy owl appeared in [[Spring Hill, Tennessee|Spring Hill]], Tennessee, the first reported sighting in the state since 1987.<ref>[https://stylingowlish.com/blogs/news/snowy-owl-appears-in-middle-tennessee "Snowy Owl Appears in Middle Tennessee."] ''The Styling Owlish.'' 24 January 2009.{{dead link|date=October 2017}}</ref> Also notable is the mass southern migration in the winter of 2011/2012, when thousands of snowy owls were spotted in various locations across the United States.<ref>Zuckerman, Laura (28 January 2012). [https://www.reuters.com/article/us-owls-migration-idUSTRE80R0MP20120128 ''Snowy owls soar south from Arctic in rare mass migration'']. Reuters</ref> This was then followed by an even larger mass southern migration in 2013/2014 with the first snowy owls seen in Florida for decades.<ref>{{cite web|last=Leung|first=Marlene Leung|title=Snowy owl invasion: Birds spotted as far south as Florida|url=http://www.ctvnews.ca/sci-tech/snowy-owl-invasion-birds-spotted-as-far-south-as-florida-1.1618624|publisher=CTV News|date=5 January 2014}}</ref><ref>{{cite news|last=Schwartz|first=John|title=A Bird Flies South, and It's News|url=https://www.nytimes.com/2014/02/01/us/influx-of-snowy-owls-thrills-and-baffles-birders.html|newspaper=New York Times|access-date=31 January 2014|date=31 January 2014}}</ref> The nature of irruptions is less well-documented in Eurasia, in part due to the paucity of this owl in the European side, but accidental occurrence, presumably during irruptions, has been described in the [[Mediterranean]] area, France, [[Crimea]], the [[Caspian sea|Caspian]] part of Iran, Kazakhstan, northern Pakistan, [[northwestern India]], Korea and Japan.<ref name= Voous/><ref name= Holt/><ref>{{cite journal|doi=10.3838/jjo.36.101|title=Records of ''Nyctea scandiaca'' from Hokkaido, Japan|year=1987|last1=Fujimaki|first1=Yuzo|journal=Japanese Journal of Ornithology|volume=36|issue=2–3|pages=101–103}}</ref> Stragglers may too turn up as far south as the [[Azores]] and Bermuda.<ref name= Konig/> ===Habitat=== [[File:Bubo scandiacus Damon Point 8.jpg|thumb|left|Snowy owls often seek out grassy and open habitats year around.]] Snowy owls are one of the best known inhabitants of the open Arctic [[tundra]]. Frequently, the earth in snowy owl breeding grounds is covered with [[moss]]es, [[lichen]]s and some [[Rock (geology)|rock]]s. Often the species preferentially occurs in areas with some rising elevation such as [[hummock]]s, [[Hillock|knolls]], [[ridge]]s, [[Bank (geography)|bluffs]] and [[Outcrop|rocky outcrops]].<ref name= Konig/><ref name= Voous/> Some of these rises in the tundra are created by [[Till|glacial deposits]].<ref name= Voous/> The ground is usually rather dry in tundra but in some areas of the southern tundra can also be quite [[marsh]]y.<ref name= Voous/> Not infrequently, they will also use areas of varied [[coast]]al habitat, often [[Mudflat|tidal flats]], as a breeding site.<ref name= Konig/><ref name= Voous/><ref name= Murie>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/condor/v031n01/p0003-p0012.pdf|author=Murie, O. J. |title=Nesting of the Snowy Owl |journal=The Condor |year=1929 |volume=31 |issue=1 |pages=3–12 |doi=10.2307/1363262|jstor=1363262 }}</ref> Breeding sites are usually at low elevations, usually less than {{convert|300|m|ft|abbr=on}} above sea level, but when breeding to the south in inland mountains, such as in Norway, they may nest at as high as {{convert|1000|m|ft|abbr=on}}.<ref name= Holt/><ref name= Parmelee/><ref name= Cramp/> Outside the breeding season, snowy owls may habituate nearly any [[Open terrain|open landscape]].<ref name= Konig/> Typically wintering sites are rather windswept with meager cover.<ref name= Hume/> These open areas can include those such as [[Dune|coastal dune]]s, other [[coast]]al spots, [[Shore|lakeshores]], islands, [[moorland]]s, [[steppe]]s, [[meadow]]s, [[prairie]]s, other extensive [[grassland]]s and rather [[shrub]]by areas of the [[Subarctic]]. These may be favored due to their vague similarity to the flat openness of the tundra.<ref name= Voous/><ref name= Hume/> Manmade open sites are now perhaps even more used than natural ones, often agricultural [[Field (agriculture)|field]]s and [[rangeland]], as well as large areas of [[Clearcutting|cleared forests]].<ref name= Holt/><ref name= Kerlinger2>{{cite journal|doi=10.1139/z85-273|title=Distribution and population fluctuations of wintering Snowy Owls (''Nyctea scandiaca'') in North America|year=1985|last1=Kerlinger|first1=P.|last2=Lein|first2=M. Ross|last3=Sevick|first3=Brian J.|journal=Canadian Journal of Zoology|volume=63|issue=8|pages=1829–1834}}</ref><ref name= Doyle>{{cite journal|doi=10.3356/JRR-16-51.1|title=Seasonal Movements of Female Snowy Owls Breeding in the Western North American Arctic|year=2017|last1=Doyle|first1=Frank I.|last2=Therrien|first2=Jean-François|last3=Reid|first3=Donald G.|last4=Gauthier|first4=Gilles|last5=Krebs|first5=Charles J.|journal=Journal of Raptor Research|volume=51|issue=4|pages=428–438|s2cid=4675025}}</ref> During irruption years when they are found in the Northeastern United States, juveniles frequent developed areas including urban areas and [[golf course]]s, as well as the expected [[grassland]]s and [[Agriculture|agricultural areas]] that older birds primarily use.<ref name= Therrien/> On the plains of Alberta, observed snowy owls spent 30% of their time in [[Crop residue|stubble-fields]], 30% in [[summer fallow]], 14% in [[hay]]field and the remainder of the time in [[pasture]], [[Grassland|natural grasslands]] and [[Slough (hydrology)|slough]]s. The agricultural areas, large untouched by the farmers in winter, may have had more concentrated prey than the others in Alberta.<ref name= Lein>{{cite journal|author1=Lein, M.R. |author2 =Webber, G.A.|year=1979|title=Habitat selection by wintering Snowy Owls (''Nyctea scandiaca'')|journal= Canadian Field-Naturalist|volume= 93|issue=2|pages=176–178}}</ref> Perhaps the most consistently attractive habitat in North America to wintering snowy owls in modern times may be airports, which not only tend to have the flat, grassy characteristics of their preferred habitats but also by winter host a particular diversity of prey, both [[Pest (organism)|pests]] which rely on humans as well as wildlife attracted to the extensively grassy and marshy strips that dot the large airport vicinities. For example, [[Logan International Airport]] in [[Massachusetts]] has one relatively one of the most reliable annual populations known in the United States in winter.<ref name= Voous/><ref name= Holt/><ref>{{cite journal|doi=10.2307/3807920|jstor=3807920|title=Raptor and Vole Populations at an Airport|last1=Baker|first1=James A.|last2=Brooks|first2=Ronald J.|journal=The Journal of Wildlife Management|year=1981|volume=45|issue=2|pages=390–396}}</ref> All ages spend a fair amount of their time over water in the [[Bering Sea]], the Atlantic Ocean and even the [[Great Lakes]], mostly on ice floes.<ref name= Weidensaul/> These marine and ocean-like freshwater areas were observed to account for 22–31% of habitat used in 34 radio-tagged American snowy owls over two irruptive years, with the tagged owls occurring a mean of {{convert|3|km|mi|abbr=on}} from the nearest land (while 35–58% used the expected preferred habitats of grassland, pasture and other agriculture).<ref name= Doyle/> ==Behavior== [[File:Bubo scandiacus Delta 6.jpg|thumb|right|Juvenile owls do not mind associating with one another, especially during winter.]] Snowy owls may be active to some extent at both day, from dawn to dusk, and night.<ref name= Konig/><ref name="Manniche" /> Snowy owls have been seen to be active even during the very brief winter daytime in the northern winter.<ref name= Voous/> During the Arctic summer, snowy owls may tend to peak in activity during the twilight that is the darkest time available given the lack of full nightfall.<ref name= Voous/><ref>Young, C.M. (1973). ''The Snowy Owl migration of 1971–72 in the Sudbury region of Ontario''. American Birds 27(1): 11–12.</ref><ref>Shields, M. (1969). ''Activity cycles of Snowy Owls at Barrow, Alaska''. Murrelet 50 (2): 14–16.</ref> Reportedly, the peak time of activity during summer is between 9:00&nbsp;pm and 3:00&nbsp;am in Norway.<ref name= Hagen>Hagen, Y. (1960). ''The Snowy Owl on Hardangervidda in the Summer of 1959''. Papers of The Norwegian State Game Research. 2, No. 7.</ref> The peak time of activity for those owls that once nested on Fetlar was reported between 10:00 and 11:00&nbsp;pm.<ref name= Tulloch>Tulloch, R. J. (1968). ''Snowy Owls breeding in Shetland in 1967''. British Birds 61:119–132.</ref> According to one authority, the least active times are at noon and midnight.<ref name= Watson/> As days become longer near autumn in [[Utqiaġvik, Alaska|Utqiaġvik]], the snowy owls in the tundra become more active around nightfall and can often be seen resting during the day, especially if it is raining.<ref>Shields, M. (1969). ''Activity cycles of Snowy Owls at Barrow, Alaska''. Murrelet 50 (2):14–16.</ref> During winter in [[Alberta]], snowy owls were tracked in the daytime, despite being also active at night (as they were deemed too difficult to track). In the study, they were most active from 8:00–10:00&nbsp;am and 4:00–6:00&nbsp;pm and often rested mostly from 10:00&nbsp;am to 4:00&nbsp;pm. The owls were perched for 98% of observed daylight and seemed to time their activity to peak times for rodents.<ref>Boxall, P. C. & Lein, M. R. (1989). ''Time budgets and activity of wintering Snowy Owls''. Journal of Field Ornithology 60 (1): 20–29.</ref> The variation of activity is probably in correspondence with their primary prey, the [[lemming]]s, and like them, the snowy owl may be considered [[Cathemerality|cathermal]].<ref name= Konig/><ref name= Voous/><ref name="National Geographic">{{cite web|title=Snowy Owl (Nyctea Scandia)|url=http://animals.nationalgeographic.com/animals/birds/snowy-owl/|website=animals.nationalgeographic.com|publisher=National Geographic|date=11 November 2010}}</ref> This species can withstand extremely cold temperatures, having been recorded in temperatures as low as minus 62.5 [[Celsius|degrees Celsius]] with no obvious discomfort and also withstood a 5-hour exposure to minus 93 degrees Celsius but may have struggled with oxygen consumption by the end of this period. The snowy owl has perhaps the second lowest [[thermal conduction]] to the plumage on average of any bird after only the [[Adelie penguin]] (''Pygoscelis adeliae'') and rivals the best insulated mammals, such as [[Dall sheep]] (''Ovis dalli'') and [[Arctic fox]], as the best insulated polar creature.<ref name= Voous/><ref name= Gessaman>Gessaman, J. A. (1972). ''Bioenergetics of the snowy owl (Nyctea scandiaca)''. Arctic and Alpine Research, 4(3), 223–238.</ref><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/condor/v057n06/p0362-p0365.pdf|author=Irving, L. |title=Nocturnal decline in the temperature of birds in cold weather|doi=10.2307/1364794}}</ref> Presumably as many as 7 rodents would need to be eaten daily to survive an extremely cold winter's day.<ref name= Voous/> Adults and young both have been seen to shelter behind rocks to shield themselves from particularly harsh winds or storms.<ref name= Holt/> Snowy owls often spending a majority of time on the ground, perched mostly on a slight rise of elevation.<ref name= Konig/> It has been interpreted from the morphology of their skeletal structure (i.e. their short, broad legs) that snowy owls are not well-suited to perching extensively in trees or rocks and prefer a flat surface to sit upon.<ref name= Potapov/> However, they may perch more so in winter though do so only mainly when hunting, at times on [[hummock]]s, [[Fence]]posts, [[telegraph pole]]s by roads, [[Radio tower|radio]] and [[transmission tower]]s, [[Hay]]stacks, [[chimney]]s and the roofs of houses and large buildings.<ref name= Voous/> Rocks may be used as perches at times in all seasons.<ref name= Voous/> Though often relatively sluggish owls, like most related species, they are capable of sudden dashing movements in various contexts.<ref name= Potapov/> Snowy owls can walk and run quite quickly, using outstretched wings for balance if necessary.<ref name= Konig/> This owl flies with fairly rowing wingbeats, occasionally interrupted by gliding on stretched wings. The flight is fairly buoyant for a ''Bubo'' owl.<ref name= Konig/><ref name= Holt/> When displaying, the male may engage in an undulating flight with interspersed wingbeats and gliding in a slight dihedral, finally dropping rather vertically to the ground.<ref name= Konig/> They are capable for swimming but do not usually do so. Some seen to be swimming were previously injured but young have been seen to swim into water to escape predators if they cannot fly yet. They will also drink when unfrozen water is available.<ref name= Holt/><ref name= Tulloch/><ref>Mebs, T. & Scherzinger, W. (2000). ''Snowy Owl''. In: ''Die eulen Europa: biolgie, kennzeichen, bestande'', edited by T. Mebs and W. Scherzinger, 167–183. Stuttgart: Franckh-Kosmos Verlags-Gmbh and Co.</ref> Snowy owl mothers have been observed to [[Preening (bird)|preen]] their young in the wild, while pairs in captivity have been observed to allopreen.<ref name= Watson/> In the period leading up to breeding, snowy owls switched regularly between searching (for nesting grounds) and loafing, often searching less when snow cover was less extensive.<ref>Therrien, J. F., Pinaud, D., Gauthier, G., Lecomte, N., Bildstein, K. L., & Bety, J. (2015). ''Pre-breeding prospecting behaviour of snowy owls'' (data from Therrien et al. 2015)-reference-data.</ref> [[File:A Snowy Owl in Flight David Hemmings.jpg|thumb|left|Snowy owls are often somewhat ponderous in movements but can be surprisingly and suddenly fast on the wing.]] Snowy owls will fight with conspecifics in all seasons occasionally but this is relatively infrequent during breeding and rarer still during winter. Dogfights and talon interlocking may ensue if the fight between two snowy owls continues to escalate.<ref name= Evans/><ref name= Watson/><ref name= Taylor/> A study determined that snowy owls are able to orient the whitest parts of their plumage towards the sun, spending about 44% of time oriented as such during sunny days and much less on cloudy days. Some authors interpret this as a presumed signal to conspecifics, but [[thermoregulation]] could also be a factor.<ref>Bortolotti, G. R., Stoffel, M. J., & Galvan, I. (2011). ''Wintering Snowy Owls Bubo scandiacus integrate plumage colour, behaviour and their environment to maximize efficacy of visual displays''. Ibis, 153(1), 134–142.</ref><ref>{{cite journal |author1= Wiebe, K. L. |author2= Chang, A. M. | year=2018| title= ''Seeing sunlit owls in a new light: orienting Snowy Owls may not be displaying.'' | journal=Ibis| volume=160| pages=62–70| doi=10.1111/ibi.12533| issue=1}}</ref> It is known that during winter in Alberta that female snowy owls are territorial towards one another and may not leave an area for up to 80 days but males are nomadic, usually only staying 1–2 days in an area (seldom to 3–17 days). The females spent on average seven times as long in a given area than did males.<ref name= Boxall>Boxall, P.C. & Lein, M.R. (1982). ''Are owls regular? An analysis of pellet regurgitation times of Snowy Owls in the wild''. Raptor Research. 16(3): 79–82.</ref> During threat displays, individuals will lower the front of the body, stretch the head low and forward, with partially extended wings and feathers on the head and raise their back.<ref name= Watson/> If continuously threatened or cornered, the posture in the threat display may become still more contoured and, if pressed, the owl will like back and attempt to slash with its large talons. The threat displays of males are generally more emphatic than those of females.<ref name= Holt/><ref>Kaufman, K. (1996). ''Lives of North American Birds''. Houghton Mifflin Company, Boston & New York.</ref> Although snowy owls have been considered as semi-colonial, they do not appear to fit this mold well. Nesting sites can be loosely clustered but this is a coincidental response to concentrated prey and each pair tends to be somewhat intolerant of each other.<ref name= Holt/><ref name= Hart>Hart, H. C. (1880). ''Notes on the ornithology of the British Polar Expedition, 1875-6''. Zoologist 4:121–129.</ref><ref>Brandt, H. (1942). ''Alaska Bird Trails: An Expedition by Dog Sled to the Delta of the Yukon River at Hooper Bay''. The Bird Research Foundation, Cleveland, OH, USA.</ref><ref>Dorogoi, I.V. (1990). ''[Factors of communal breeding of the Snowy Owls (Nyctea scandiaca) and Anseriformes birds at the Vrangel Island]''. Ornitologiya. 24: 26–33. In Russian with English summary.</ref> During winter, snowy owls are usually solitary but some [[Aggregation (ethology)|aggregation]]s have been recorded, especially nearer the Arctic when more narrow food selection can lead to up to 20–30 owls gathering in an area of about {{convert|20|to|30|ha|acre|abbr=on}}.<ref name= Holt/><ref name= Pitelka2>Pitelka, F. A., Tomich, P. Q. & Treichel, G.W. (1955). ''Ecological relations of jeagers and owls as Lemming predators near Barrow, Alaska''. Ecological Monographs 25: 85–117.</ref> Congregations were also recorded in the winter in Montana, where 31–35 owls wintered in a {{convert|2.6|km2|sqmi|abbr=on}} area, owls mostly grouped in loose aggregations of 5–10 owls each or occasionally side-by-side or about {{convert|20|m|ft|abbr=on}} apart.<ref name= Holt2>Holt, D. W. & Zetterberg, S. A. (2008). ''The 2005 to 2006 Snowy Owl irruption migration to western Montana''. Northwestern Naturalist 89 (3):145–151.</ref> In extreme cases in Utqiaġvik, the owls may have exceptionally close active nests that may be down to only {{convert|800|to|1600|m|ft|abbr=on}} apart.<ref name= Pitelka/> Juvenile males appear to be especially prone to loose associations with one another, appearing to be non-territorial and able to hunt freely in front of one another.<ref name= Holt/> In a {{convert|213|km2|sqmi|abbr=on}} area in and around Utqiaġvik, productive years may have about 54 nests while none may be found in poor years.<ref name= Holt/> Utqiaġvik may have about 5 owls in early summer every {{convert|1.6|km|mi|abbr=on}}, have a nest spacing of {{convert|1.6|to|3.2|km|mi|abbr=on}} and the owls territory size is about {{convert|5.2|to|10.2|km2|sqmi|abbr=on}}.<ref name= Holt/> In [[Churchill, Manitoba]], nest spacing averaged about {{convert|3.2|km|mi|abbr=on}}.<ref name= Shelford>Shelford, V. E. (1943). ''The abundance of the Collared Lemming (Dicrostonyx groenlandicus (TR) VAR. Richardsoni Mer.) in the Churchill area, 1929 to 1940''. Ecology 24 (4):472–484.</ref> In [[Southampton Island]] in a year when the owls nested there, nest spacing averaged {{convert|3.5|km|mi|abbr=on}}, with the closest two {{convert|1|km|mi|abbr=on}} apart and density per nest was {{convert|22|km2|sqmi|abbr=on}}.<ref>Parker, G. R. (1974). ''A population peak and crash of lemmings and Snowy Owls on Southampton Island, Northwest Territories''. Canadian Field-Naturalist. 88(2): 151–156.</ref> In Nunavut, densities could go from 1 owl per {{convert|2.6|km2|sqmi|abbr=on}} in a productive year to 1 owl per {{convert|26|km2|sqmi|abbr=on}} in a poor year and from 36 nests in a {{convert|100|km2|sqmi|abbr=on}} area to none at all.<ref name= Manning>Manning, T. H., Höhn, E. O. & MacPherson, A. H. (1956). ''The birds of Banks Island''. National Museum of Canada Bulletin 143, Biological Series 48.</ref><ref>Vaughn, R. (1992). ''In search of Arctic birds''. London: T & AD Poyser, Ltd.</ref> Owl density on Wrangel Island in Russia was observed be a single bird each {{convert|0.11|to|0.72|km2|sqmi|abbr=on}}.<ref name= Menyushina>Menyushina, I. E. (1997). ''Snowy Owl (Nyctea scandiaca) reproduction in relation to lemming population cycles on Wrangel Island''. In: ''Biology and conservation of owls of the Northern Hemisphere: 2nd International Symposium'', edited by J. R. Duncan, D. H. Johnson and T. H. Nicholls, 572–582. St. Paul: U.S. Dept. of Agriculture, Forest Service, North Central Forest Experiment Station.</ref> The first known study of winter territories took place in [[Horicon Marsh]] where owls ranged from {{convert|0.5|to|2.6|km2|sqmi|abbr=on}} each.<ref name= Keith/> In [[Calgary, Alberta]], mean territory size of juvenile females in winter was {{convert|407.5|ha|acre|abbr=on}} and adult females was {{convert|195.2|ha|acre|abbr=on}}.<ref name= Boxall/> Wintering owls in central Saskatchewan were radio-monitored, determining that 11 males had an average range of {{convert|54.4|km2|sqmi|abbr=on}}, while that of 12 females was {{convert|31.9|km2|sqmi|abbr=on}} with the combined average being {{convert|53.8|km2|sqmi|abbr=on}}.<ref>Chang, A. M., & Wiebe, K. L. (2018). ''Movement patterns and home ranges of male and female Snowy Owls (Bubo scandiacus) wintering on the Canadian prairies''. Canadian Journal of Zoology, 96(6), 545–552.</ref> [[File:Bubo scandiacus Delta 4.jpg|thumb|left|Snowy owls are usually awake, aware and not infrequently active during daytime.]] ===Migration=== It is fair to say that the snowy owl is a partial, if fairly irregular, [[Bird migration|migrant]], having a very broad but patchy wintering range.<ref name= Konig/> 1st year birds tend to disperse farther south in winter than older owls with males wintering usually somewhat more to the south than females of equivalent ages, adult females often wintering the farthest north.<ref name= Voous/><ref name= Scandinavica>Kerlinger, P. & Lein, M.R. (1986). ''Differences in winter range among age-sex classes of Snowy Owls Nyctea scandiaca in North America''. Ornis Scandinavica. 17(1): 1–17.</ref> The snowy owl likely covers more ground than almost any other owl in movements but many complex individual variations are known in movements, and they often do not take the traditional north–south direction that might be assumed.<ref name= Holt/> Migratory movements appear to be somewhat more common in America than in Asia.<ref name= Konig/> A study of wintering owls in the [[Kola Peninsula]] determined that the mean date of arrival of owls was 10 November with a departure date of 13 April, covering an average of {{convert|991|km|mi|abbr=on}} during the course of the wintering period and clustering where [[Ptarmigan|prey]] was more concentrated.<ref>Øien, I. J., Aarvak, T., Jacobsen, K. O., & Solheim, R. (2018). ''Satellite Telemetry Uncovers Important Wintering Areas for Snowy Owls On the Kola Peninsula, Northwestern Russia''. Орнитология, 42, 42–49.</ref> Some variety of movements recorded each autumn and snowy owls winter annually in plains of [[Siberia]] and Mongolia and [[prairie]]s and [[marsh]]lands of Canada.<ref name= Voous/> The [[Great Plains]] area of southern Canada host wintering snowy owls about 2 to 10 times more frequently than other areas of the continent.<ref name= Holt/> Some weak correlation has made with individuals having some level of fealty to certain wintering sites.<ref>Oeming, A. F. (1957). ''Notes on the Barred Owl and the Snowy Owl in Alberta''. Blue Jay 15:153–156.</ref><ref>Follen, D. & Luepke, K. (1980). ''Snowy Owl recaptures''. Inland Bird Banding 52: 60.</ref> Wintering snowy owls, a total of 419, recorded in [[Duluth, Minnesota]] from 1974 to 2012 would occur in larger numbers in years where [[Brown rat|rats]] were more plentiful. The amount of individual returns among 43 Duluth-wintering owls was fairly low in subsequent winters (8 for 1 year, a small handful in the next few years, and 9 in non-consecutive years).<ref name= Holt/> Sometimes surveys appeared to reveal hundreds of wintering snowy owls on coastal sea ice during an irruptive year.<ref name= Voous/><ref name= Marine/> Three siblings that hatched in same nest in [[Cambridge Bay]] were recovered in drastically different spots at least a year later: one in eastern [[Ontario]], one in [[Hudson Bay]] and one in [[Sakhalin Island]].<ref name= Parmelee/> A nestling banded in [[Sogn og Fjordane|Hordaland]] was recovered {{convert|1380|km|mi|abbr=on}} to the northeast in [[Finnmark]].<ref name= Voous/> In the [[Logan Airport]], 17 of 452 owls were recorded to return, eleven the following year, three 2 years later, and then singles variously 6, 10 and 16 years later.<ref name= Holt/> A banded female from Utqiaġvik was recorded to migrate over {{convert|1928|km|mi|abbr=on}} along seacoast down to Russia, returning over {{convert|1528|km|mi|abbr=on}} and covering at least {{convert|3476|km|mi|abbr=on}} in total. Another banded young female from Utqiaġvik went to the same Russian areas, returned to Utqiaġvik and then onto [[Victoria Island (Canada)|Victoria Island]], but did appear to breed, while another also covered a similar route but ended up nesting on [[Banks Island]]. Another female migrated to the [[Canada–United States border]], then moved back to the [[Gulf of Alaska]], then to winter in the same border areas and then finally to both Banks and Victoria Island.<ref name= Holt/><ref name= Fuller/> Snowy owls from the Canadian Arctic were monitored to have covered an average of {{convert|1100|km|mi|abbr=on}} in one autumn then covered an average of {{convert|2900|km|mi|abbr=on}} a year later.<ref name= Therrien2>Therrien, J.-F., Fitzgerald, G., Gauthier G. & Bêty, J. (2011). ''Diet-tissue discrimination factors of carbon and nitrogen stable isotopes in blood of Snowy Owl (Bubo scandiacus)''. Canadian Journal of Zoology 89 (4): 343–347.</ref> In late winter, owls from the same area were found to have covered a mean of {{convert|4093|km|mi|abbr=on}} of ground in the tundra and spent a mean of 108 days, apparently searching for a suitable nesting situation the entire time.<ref>Therrien, J.-F. , Gauthier, G., Pinaud, D. & Bêty, J. (2014). ''Irruptive movements and breeding dispersal of Snowy Owls: a specialized predator exploiting a pulsed resource''. Journal of Avian Biology. 45(6): 536–544.</ref> In no fewer than 24 winters between 1882 and 1988, large numbers have occurred in Canada and the United States. These were [[Irruptive growth|irruption]] years.<ref name= Voous/> Record breeding irruptive years were recorded in the winters of 2011–2012 and 2014–2015.<ref name= Holt/><ref>Jorgensen, J. G., Dinan, L. R., & Walker Jr, T. J. (2012). ''Snowy Owl Invasion of 2011–12''.</ref> In the 1940s, it was calculated that the mean gape in time between large irruptions was 3.9 years.<ref name= Gross1/> Southbound movements as such are much more conspicuous after peak vole years, once thought to be separated by periods of around 3–7 years.<ref name= Voous/><ref>Snyder, L. L. (1943). ''The Snowy Owl migration of 1941–42''. Wilson Bulletin 55 (1):8–10.</ref><ref>Shelford, V. E. (1945). ''The relation of Snowy Owl migration to the abundance of the Collared Lemming''. Auk 62 (4):592–596.</ref><ref>Chitty, H. (1950). ''Canadian Arctic wild life enquiry, 1943–1949: With a summary of results since 1933''. Journal of Animal Ecology 19 (2):180–193.</ref><ref name="Godfrey" /> However, more extensive research has weakened the argument that irruptions are entirely food-based and the data indicates that irruptive movements are far from predictable. This is because a statewide survey in Alaska found no statewide synchrony in lemming numbers. Therefore, rather than decline of lemmings, it is the successful productivity of several pairs that plays the role, resulting in a large number of young owls that then irrupt. However, the snowy owls cannot breed in high numbers unless lemmings are widely available on the tundra.<ref name= Holt/><ref name= Kerlinger2/><ref name= Gross/><ref>Pitelka, F. A. & Batzli, G. O. (1993). ''Distribution, abundance, and habitat use by lemmings on the north slope of Alaska''. In: ''The biology of lemmings'', edited by N. C. Stenseth and R. A. Ims, 213–236. London: Academic Press.</ref><ref name="Krebs">Krebs, C. J. (1993). ''Are lemmings large Microtus or small reindeer? A review of lemming cycles after 25 years and future recommendations for future work''. In: ''The biology of lemmings'', edited by N. C. Stenseth and R. Ims, 247–260. London: Academic Press for the Linnean Society of London.</ref> This connection of irruptions to high years of productivity was confirmed in a study by Robillard et al. (2016).<ref>Robillard, A., Therrien, J. F., Gauthier, G., Clark, K. M., & Bêty, J. (2016). ''Pulsed resources at tundra breeding sites affect winter irruptions at temperate latitudes of a top predator, the snowy owl''. Oecologia, 181(2), 423–433.</ref> About 90% of the snowy owls seen in irruptive years from 1991 to 2016 that were ageable were identified as juveniles.<ref name= Santonja/> ==Feeding== ===Hunting techniques=== [[File:Harfang en vol 1.jpg|thumb|right|A snowy owl engaging in the "sweep" hunting method.]] Snowy owls may hunt at nearly at any time of the day or night, but may not attempt to do so during particularly severe weather.<ref name= Holt/> During the [[summer solstice]], the owls appear to hunt during "theoretical nightfall".<ref name= Holt/> [[Night-vision device]]s have allowed biologists to observe that snowy owls hunt quite often during the extended nighttime during the northern winter.<ref name= Potapov/><ref name= Holt/><ref name="Manniche" /> Prey are both taken and eaten on the ground.<ref name= Konig/> Snowy owls, like other carnivorous birds, often swallow their small prey whole.<ref name= Konig/> Strong stomach juices digest the flesh, while the indigestible bones, teeth, fur, and feathers are compacted into oval pellets that the bird regurgitates 18 to 24 hours after feeding. Regurgitation often takes place at regular perches, where dozens of pellets may be found. Biologists frequently examine these pellets to determine the quantity and types of prey the birds have eaten. When large prey are eaten in small pieces, pellets will not be produced.<ref>[http://www.owlpages.com/owls.php?genus=Bubo&species=scandiacus Snowy Owl — ''Bubo scandiacus'', formerly ''Nyctea scandiaca'']. owlpages.com</ref> Larger prey is often torn apart, sometimes include removal of the head, with the large muscles, such as the [[humerus]] or [[Thorax|breast]], typically eaten first.<ref name= Holt/> The scattering of remains that results from the increment feeding on larger prey is thought to result in under-identification of them compared to smaller prey items.<ref>{{cite journal|title=A taphonomic investigation of small vertebrate accumulations produced by the snowy owl (''Bubo scandiacus'') and its implications for fossil studies|doi=10.1016/j.palaeo.2018.10.018}}</ref> The aptitude for hunting by day, hunting from the ground and hunting in almost always completely open and treeless areas are the primary ways in which the snowy owl differs in hunting from other ''Bubo'' owls. Otherwise, the hunting habits are similar.<ref name= Holt/><ref name= Johnsgard>[[Paul Johnsgard|Johnsgard, P. A.]] (1988). [https://digitalcommons.unl.edu/johnsgard/46/ ''North American owls: biology and natural history'']. Smithsonian Institution.</ref> It is thought, due to their less refined hearing compared to other owls, prey is usually perceived via vision and movement.<ref name= Voous/><ref name= Holt/> Experiments indicate that snowy owls can detect prey from as far as {{convert|1.6|km|mi|abbr=on}} away.<ref name= Smith/> Snowy owls generally use a rise or, occasionally, a perch while hunting.<ref name= Konig/> 88% of observed 34 hunts in Utqiaġvik were undertaken from an elevated watch-site (56% mounds or rises, 37% [[telephone pole]]s).<ref name= Holt/> Their hunting style may recall that of [[Buteo|buzzard]]s, with the hunting owl sitting rather low and perching immobile for a long spell.<ref name= Hume/> Although their usual flight is a slow, deliberate downbeat on the broad, fingered wings, when prey is detected from their perch, flight may undertaken with a sudden, surprisingly quick accelerated style with interspersed wing beats.<ref name= Hume/><ref>{{cite journal|author=Hohn, E. O. |year=1973|title=Winter hunting of Snowy Owls in farmland|journal= Canadian Field-Naturalist|volume= 87 |issue=4|pages= 468–469}}</ref> In Utqiaġvik, snowy owls may most frequently engage in a brief pursuit hunting style.<ref name= Holt/> In high winds capable of keeping their bulk aloft, snowy owls may too engage in a brief [[Levitation|hovering]] flight before dropping onto prey.<ref name= Watson/> When hunting fish, apparently, some snowy owls will hover in a style reminiscent of the [[osprey]] (''Pandion haliaetus''), although in at least one other case a snowy owl was observed to capture fish by lying on its belly upon a rock by a fishing hole.<ref name= Audubon>Audubon, J. J. (1840). ''The Birds of America''. Dover Publications, Inc., New York, NY, USA.</ref> A dashing stoop or pounce down onto their prey, ending in a high-impact "wallop", is fairly commonly recorded.<ref name= Holt/><ref name= Hume/> Another common technique is the "sweep", wherein they fly by and grasp the prey while continuing to fly.<ref name= Holt/><ref>{{cite journal|author=Dancey, H.E. |year=1983|title=Winter foraging habits of a Snowy Owl|journal= Indiana Audubon Quarterly|volume= 61|issue=4|pages= 136–144}}</ref> In winter, snowy owls have been shown to be able to "snow plunge" to capture prey in the [[Subnivean climate|subnivean zone]], under at least {{convert|20|cm|in|abbr=on}} of snow.<ref name= Smith/> Perhaps least frequently, snowy owls may pursue their on foot, in doing so never taking wing.<ref name= Holt/> Snowy owls have been known to capture [[Bird migration|night-migrating]] [[passerine]]s and [[shorebird]]s, sometimes perhaps on the wing, as well as large and/or [[Bird of prey|potentially dangerous]] birds that were caught in air by snowy owls during daylight.<ref name= Holt/> On the wing pursuits against other various other carnivorous birds are sometimes undertaken as well to [[Kleptoparasitism|kleptoparasitize]] the prey caught by the other birds.<ref name= Holt/><ref>Duffy, D. C., Beehler B. & Haas, W. (1976). ''Snowy Owl steals prey from Marsh Hawk''. Auk 93 (4): 839–840.</ref> Few variations of hunting technique were observed in winter observations from [[Alberta]], almost all of the hunts being with the sit-and-wait method (also known as still-hunts). Adult females in Alberta had a considerably better hunting rate than juvenile females.<ref name= Boxall2>{{cite journal|doi=10.14430/arctic2326|title=Feeding ecology of Snowy Owls (''Nyctea scandiaca'') wintering in S. Alberta}}</ref> Much as in Alberta, in [[Syracuse, New York]], 90% of 51 hunts were still-hunting, with the sweep variant used after perch departure in 31% of hunts and the pounce method in 45% of hunts. The Syracuse-wintering owls used tall perches, a mixture of manmade objects and trees of around {{convert|6|m|ft|abbr=on}} high, in nearly 61% of hunts, while nearly 14% were from low perches (i.e. fence-posts, snow banks and scrap piles) about half as high as the tall perches and started from a ground position nearly 10% of the time.<ref name= Winter>Winter, R. E. (2016). ''Hunting Behaviors and Foraging Success of Winter Irruptive Snowy Owls in New York''. SUNY College of Environmental Science and Forestry, Thesis.</ref> In Sweden, males hunted from a perch more so than did females and adults both focused on significantly smaller prey (small [[mammal]]s) and may have had more success hunting than juvenile snowy owls.<ref name= Lind/> Some snowy owls can survive a fast for up to about 40 days off of [[Fatty acid metabolism|fat reserves]].<ref name= Hume/> These owls were found to have extremely thick [[Subcutaneous tissue|subcutaneous fat deposits]] of around {{convert|19|to|22|mm|in|abbr=on}} and it is likely owls that overwinter in the Arctic rely heavily on these to survive during this scarce time, in combination with lethargic, energy-conserving behavior. Snowy owls may not infrequently exploit prey inadvertently provided or compromised by human activities, including ducks injured by [[Hunting|duck hunters]], [[Red phalarope|birds]] maimed by [[Antenna (radio)|antenna]] wires, various animals caught in human [[Trapping|traps]] and [[trapline]]s as well as [[Domestication of animals|domestic]] or wild prey being bred or farmed by humans in enclosures.<ref name= Watson/><ref name=Wiggins/><ref>Brooks, W. S. (1915). ''Notes on birds from east Siberia and Arctic Alaska''. Bulletin of the Museum of Comparative Zoology 59:361–413.</ref><ref>Nagell, B. & Frycklund, I. (1965). ''The irruption of the Snowy Owl (Nyctea scandiaca) in Scandinavia in the winters of 1960–1963 and notes on its behavior''. Vår Fågelvärld 24 (1): 26–55.</ref><ref>King, B., Nayler, F. & Wardle, F. (1966). ''Feeding and resting behavior of a Snowy Owl in Scilly''. British Birds 59 (3): 108.</ref><ref name= Robertson>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/jrr/v037n02/p00164-p00166.pdf|author1=Robertson, G. J. |author2=Gilchrist, H. G. |year=2003|title=Wintering Snowy Owls feed on sea ducks in the Belcher Islands, Nunavut, Canada|journal= Journal of Raptor Research |volume=37 |issue=2|pages= 164–166}}</ref> A wide variety of accrued reports show that the snowy owl that [[Scavenger|scavenging]] on [[carrion]] is not uncommon (despite having once been thought to be very rare in all owls), including instances of [[reindeer]] (''Rangifer tarandus'') body parts brought to nests and owls following [[polar bear]]s to secondarily feed on their kills. Even huge [[marine mammal]]s such as [[walrus]] (''Odobenus rosmarus'') and whales can be fed upon by these owls when the opportunity occurs.<ref name= Holt/><ref>{{cite journal|doi=10.3356/0892-1016-53.4.410}}</ref> Snowy owls produce a [[Pellet (ornithology)|pellet]] that in different areas averages a median of about {{convert|80|x|30|mm|in|abbr=on}}, averaging up to {{convert|92|mm|in|abbr=on}} in length as in Europe.<ref name= Cramp/><ref name= Detienne/><ref name= Patterson/><ref name= Hagen/> ===Prey spectrum=== [[File:Snowy Owl (240865007).jpeg|thumb|left|A snowy owl flying with an unidentified prey item in winter.]] The snowy owl is primarily a hunter of [[mammal]]s.<ref name= Konig/> Most especially, they often live off of the northerly [[lemming]]s.<ref name= Konig/><ref name= Sutton/><ref name= Watson/> Sometimes other similar rodents like [[vole]]s can also be found frequently in the snowy owl's foods.<ref name= Konig/> It is [[r/K selection theory|R-selected]], meaning that it is an opportunistic breeder capable of taking advantage of increases in prey numbers and diversity, despite its apparent specialization.<ref name= Potapov/> Birds are commonly taken as well, and may regularly include [[passerine]]s, northern [[seabird]]s, [[ptarmigan]] and ducks, among others.<ref name= Konig/> Sometimes infrequent consumption of other prey such as [[beetle]]s, [[crustacean]]s and occasionally [[amphibian]]s and fish is reported (of these only fish are known to have been identified to prey species).<ref name= Konig/><ref name= Bent/><ref name= Detienne>{{cite journal|doi=10.3356/JRR-07-41.1}}</ref> All told, more than 200 prey species have been known to be taken by snowy owls around the world.<ref name= Voous/><ref name= Potapov/><ref name= Holt/> Generally, like other large owls (including even bigger owls like the [[Eurasian eagle-owl]]), prey selection tends toward quite small prey, usually small [[mammal]]s, but they can alternate freely with prey that is much larger than typical given the opportunity or even bigger than themselves, including relatively large mammals and several types of large bird of almost any age.<ref name= Voous/><ref name= Holt/><ref name= Marti>Marti, C. D., Korpimäki, E., & Jaksić, F. M. (1993). "Trophic structure of raptor communities: a three-continent comparison and synthesis". In ''Current ornithology'' (pp. 47–137). Springer, Boston, MA.</ref> One study estimated for the [[biome]]s of [[Alaska]] and Canada, mean prey sizes for snowy owls were {{convert|49.1|g|oz|abbr=on}}, in [[western United States|western North America]], the mean prey size was {{convert|506|g|lb|abbr=on}} and in [[eastern United States|eastern North America]] was {{convert|59.7|g|oz|abbr=on}}, while the mean prey size in northern [[Fennoscandia]] was similar (at {{convert|55.4|g|oz|abbr=on}}). The mean number of prey species for snowy owls per biome ranged from 12 to 28.<ref name= Marti/> The opportunistic nature of snowy owls has long been known during their primarily winter observed feeding habits (leading to their unpopular nature and frequent persecution well into the 20th century).<ref name= Holt/><ref name= Bent/><ref name= Detienne/><ref name= Robinson>Robinson, M. & Becker, C.D. (1986). ''Snowy Owls on Fetlar''. British Birds. 79(5): 228–242.</ref> ===Summer diet=== [[File:Lemmuslemmus.jpg|thumb|right|[[Lemming]]s such as [[Norway lemming]]s are the primary prey of breeding snowy owls.]] The snowy owl's biology is closely tied to the availability of [[lemming]]s. These herbivorous rodents are largish members of the vole clan that are the predominant mammal of the tundra ecosystem alongside the reindeer and probably make up the majority of the mammalian [[biomass]] of the ecosystem. Lemmings are key architects of the soil, [[Topography|microtopography]] and plant life of the entire tundra.<ref>McKendrigk, J. D., Batzli, G. O., Everett, K. R., & Swanson, J. C. (1980). ''Some effects of mammalian herbivores and fertilization on tundra soils and vegetation''. Arctic and Alpine Research, 12(4), 565–578.</ref><ref name="Shelford" /><ref name="Krebs" /><ref>Fitzgerald, B.M. (1981). Predatory birds and mammals. In Tundra ecosystems: a comparative analysis (Eds L.C. Bliss, 0.W. Heal & J.J. Moore), pp. 485–508. Cambridge University Press, Cambridge.</ref> In the American lower Arctic areas, [[True lemming|brown lemming]] of the ''Lemmus'' genus are predominant and tend to be found in lower, wetter habitats (feeding by preference on grasses [[sedge]]s and [[moss]]es) while [[collared lemming]]s of the ''Dicrostonyx'' genus were in more arid, often higher elevation habitats with [[heath]]land and ate by preference [[willow]] [[Leaf|leaves]] and [[forb]]s.<ref>{{cite journal|doi=10.2307/1550496}}</ref> The southerly brown lemmings behave differently than more northern collared lemming type, increasing almost limitlessly within preferred habitat whereas the collared type tends to spread to suboptimal habitats and therefore does not appear reach the high regional densities of the brown.<ref name= Voous/> Authorities now generally agree that there appears to be no synchrony between the brown and collared lemmings and the feeding access of snowy owls is irregular as a result, but snowy owls can likely alternate between the two lemming types as one or the other increases as they nomadically use different parts of the Arctic. It is possible that the rare coincidental mutual peak of both lemming types within a year results in the erratic high productivity that results in irruptions.<ref name= Voous/><ref name= Holt/> Within individual Arctic lemming species, historically, populations can vary in rough 4- to 5-year trends.<ref name= Hume/> As a result, in areas such as [[Banks Island]], the breeding rate of snowy owls can vary within a decade by about tenfold.<ref name= Voous/><ref name= Hume/> Weights of lemmings taken can range from {{convert|30|to|95|g|oz|abbr=on}} on [[Baffin Island]], while those taken in Utqiaġvik averaged {{convert|70.3|and|77.8|g|oz|abbr=on}} in female and male lemming, respectively.<ref name= Holt/><ref name= Watson/> It was estimated based on captive daily food intake that a snowy owl may consume about {{convert|326|g|oz|abbr=on}} of lemmings a day, though other estimates using voles show a daily need for about {{convert|145|to|150|g|oz|abbr=on}}.<ref name= Seidensticker/><ref name= Pitelka/><ref name= Detienne/> On [[Southampton Island]], 97% of the diet was lemmings.<ref name= Parker>{{cite journal|author=Parker, G.R. |year=1974|title=A population peak and crash of lemmings and Snowy Owls on Southampton Island, Northwest Territories|journal= Canadian Field-Naturalist|volume= 88|issue=2|pages=151–156}}</ref> A very similar number of lemmings (nearly 100%) were found over 25 years of study in Utqiaġvik, amongst 42,177 cumulative prey items.<ref name= Holt/> Of 76 lemmings that could be identified to sex at a [[Hoarding (animal behavior)|cache]], male lemmings were found in the cache twice as often as female lemmings.<ref name= Pitelka/> While initial findings indicated on [[Wrangel Island]] that female lemmings outnumbered males in prey remains, to the contrary osteology indicated that, like Utqiaġvik, males were more often taken. However, the slightly larger, slower-moving females may be preferred when available.<ref name= Krechmar>Krechmar, A.V. & Dorogoy, I.V . (1981). "Snowy Owl (''Nyctea scandiaca'')". In: ''Ecology of mammals and birds in Wrangel Island''. Vladivostok: DVNZ AN SSSR: pp. 56–81.</ref> In some areas, snowy owls can breed where lemmings are uncommon to essentially absent.<ref name= Holt/> Even in Utqiaġvik, where the diet is quite homogenously based in lemmings, the hatching of [[passerine]]s, [[shorebird]]s and [[waterfowl]] can provide a key resource when lemmings are not found regularly and may be the only means by which the young can survive at such lean times.<ref name= Holt/> In the [[Nome, Alaska]] area, the locally nesting snowy owls reportedly switched from lemmings to [[ptarmigan]]s when the latter's chicks hatched.<ref name= Dufresne>{{cite journal|author=Dufresne, F. |year=1922|title=The Snowy Owl-destroyer of game|journal= Bull. Amer. Game Prot. Assoc. |volume=11|pages= 11–12}}</ref> A somewhat varying diet was also reported in [[Prince of Wales Island (Nunavut)|Prince of Wales Island, Nunavut]] where 78.3% of the biomass was lemmings, with 17.8% from [[waterfowl]], 3.3% from [[Stoat|weasel]] and about 1% from other birds.<ref name= Voous/> In [[Fennoscandia]], among 2,700 prey items only a third were [[Norway lemming]]s (''Lemmus lemmus'') and a majority were [[vole]]s at 50.6%, probably largely the [[tundra vole]] (''Microtus oeconomus'').<ref name= Voous/><ref name= Cramp/> A more detailed glance at [[Lapland (Finland)|Finnish Lapland]] showed that amongst 2,062 prey items, 32.5% of the foods were Norway lemmings (though in some years the balance could range up to 58.1%), 28% were [[grey red-backed vole]]s (''Myodes rufocanus'') and 12.6% were tundra voles, with birds constituting a very small amount of the prey balance (1.1%).<ref name= Hakala>{{cite journal|author=Hakala, A., Huhtala, K., Kaikusalo, A., Pulliainen, E., & Sulkava, S. |year=2006|title=Diet of Finnish snowy owls ''Nyctea scandiaca''|journal= Ornis Fennica|volume= 83|issue=2|pages=59}}</ref> In northern Sweden, a more homogenous diet was found with the Norway lemming constituting about 90% of the foods.<ref name= Andersson>{{cite journal|author=Andersson, N. Å. & Persson, B. |year=1971|title=Något om fjällugglans Nyctea scandiaca näringsval i Lappland|journal= Vår Fågelvärld |volume=30|pages= 227–231}}</ref> In the [[Yamal Peninsula]], 40% of the diet was collared lemmings, 34% were [[Siberian brown lemming]] (''Lemmus sibiricus''), 13% were ''[[Microtus]]'' voles and [[Willow ptarmigan|ptarmigan]] and ducks both constituting 8% and with other birds making up much of the remaining balance.<ref>Osmolovskaya, V.N. 1948. ''[Ecology of raptors on the Yamal peninsula]''. – Proc. Inst. Geography, Academy of Sciences of the USSR 61: 4–77 (in Russian).</ref> In some parts of the tundra, snowy owls may opportunistically prey upon [[Arctic ground squirrel]]s (''Spermophilus parryii'').<ref>{{cite journal|doi=10.1644/10-MAMM-A-030.1|title=Habitat selection by arctic ground squirrels (''Spermophilus parryii'')}}</ref> In the [[Hooper Bay]] area (much farther south than they usually nest), various rodents, in highland areas, and [[waterfowl]], in marshland, were taken while breeding.<ref name= Murie/><ref>Brackney, A. W. & King, R. J. (1991). ''Population shifts by Snowy Owls on the Arctic coastal plain of Alaska. Abstract''. In Alaska Bird Conference and Workshop. Anchorage.</ref> When historically breeding on [[Fetlar]] in Shetland, the main prey for snowy owls was [[European rabbit]]s (''Oryctolagus cuniculus''), [[Eurasian oystercatcher]] (''Haematopus ostralegus''), [[parasitic jaeger]]s (''Stercorarius parasiticus'') and [[Eurasian whimbrel]] (''Numenius phaeopus''), in roughly that order, followed by other bird species with most (rabbits and secondary birds) prey taken as adults but for the oystercatchers and jaegers which were taken largely as fully grown but only recently fledged juveniles. 22–26% of oystercatcher and jaeger young in the island were estimated to be taken by snowy owls.<ref name= Tulloch/><ref name= Robinson/> Bird predation by nesting snowy owls is highly opportunistic.<ref name= Holt/> [[Willow ptarmigan|Willow]] (''Lagopus lagopus'') and [[rock ptarmigan]] (''Lagopus muta'') of any age are often fairly regular in the diet of breeding snowy owls but they cannot be said to particularly specialize on these.<ref name= Potapov/><ref>{{cite journal|jstor=40511025|doi=10.14430/arctic2091}}</ref><ref name= Potapova>{{cite journal|author=Potapova, O. |year=2001|title=Snowy owl ''Nyctea scandiaca'' (Aves: Strigiformes) in the Pleistocene of the Ural Mountains with notes on its ecology and distribution in the Northern Palearctic|journal= Deinsea|volume= 8|issue=1|pages= 103–126}}</ref> Evidence was found in the [[Yamal Peninsula]] that the snowy owls became the primary predator of willow ptarmigan and that the predation was so frequent, it may have been the cause of the change of their habitat usage to [[willow]] thickets by the local ptarmigan.<ref>Tarasov, V. V. (2011). ''Summer flocks of the Willow Ptarmigan in the north of the Yamal Peninsula''. In: R. T. Watson, T. J. Cade, M. Fuller, G. Hunt, and E. Potapov (Eds.). ''Gyrfalcons and Ptarmigan in a Changing World''. The Peregrine Fund, Boise, Idaho, USA.</ref> The reliance on ptarmigan has caused some conservation trickle-down concern for the owls because ptarmigan are hunted in large numbers, with the hunters of Norway permitted to cull up to 30% of the regional population.<ref name= Heggoy/> In North America, avian prey on the breeding ground regularly varies from small passerines like [[snow bunting]]s (''Plectrophenax nivalis'') and [[Lapland longspur]]s (''Calcarius lapponicus'') to large waterfowl like [[King eider|king]] (''Somateria spectabilis'') and [[common eider]] (''Somateria mollissima'') and usually the goslings but also occasionally adults of geese such as [[Brant (goose)|brant]]s (''Branta bernicla''), [[snow geese]] (''Anser caerulescens'') and [[cackling geese]] (''Branta hutchinsii'').<ref name= Potapov/><ref name= Holt/><ref name= Manning/><ref>{{cite journal|doi=10.1093/auk/90.2.433}}</ref> Drake eiders of often similar size to the owls themselves are not infrequently the largest prey amongst remains around the nest mound. One nest had the bodies of all eiders that attempting to nest in the vicinity around it.<ref name= Potapov/><ref name= Holt/><ref name= Dorogoy>Dorogoy, I.V . (1987). ''Ecology of small mammal predators in Wrangel Island and their role in the dynamics of lemming numbers''. Vladivostok: DVO AN SSSR. (In Russian).</ref><ref name= Wiggins>{{cite journal|doi=10.2307/4081330|title=Foraging activities of the Snowy Owl (''Nyctea scandiaca'') during a period of low lemming population}}</ref> The threatened and declining [[Steller's eider]] (''Polysticta stelleri'') when nesting in the Utqiaġvik area would appear to avoid the vicinity of snowy owl nests when selecting their own nesting sites due to the predation risk.<ref>{{cite journal|doi=10.14430/arctic493|title=Breeding biology of Steller's eiders (''Polysticta stelleri'') near Barrow, Alaska, 1991–99}}</ref> Intermediately sized [[seabird]]s are often focused on in lieu of available lemmings.<ref name= Holt/> Foods were studied intensively in Iceland. Among 257 prey items found with a total prey mass of {{convert|73.6|kg|lb|abbr=on}}, birds made up 95% of the diet. The leading prey were adult [[rock ptarmigan]], at 29.6% by number and 55.4% by biomass and adult [[European golden plover]] (''Pluvialis apricaria''), at 10.5% by number and 7.2% biomass. The rest of the balance was largely other [[shorebird]]s, which were taken slightly more often as chicks than adults. [[Pink-footed geese]] (''Anser fabalis'') were taken in equal number as goslings and adults, with respectively estimated average weights at these ages of {{convert|800|and|2470|g|lb|abbr=on}}.<ref name= Stenkewitz>Stenkewitz, U., & Nielsen, Ó. K. (2019). ''The Summer Diet of the Snowy Owl (Bubo scandiacus) in Iceland''. Journal of Raptor Research, 53(1), 98–101.</ref> On the isle of [[Agattu]], the diet consisted entirely of birds, as there are no mammals found there.<ref name= Williams>{{cite journal|doi=10.2307/1367296|url=https://sora.unm.edu/sites/default/files/journals/condor/v081n02/p0213-p0214.pdf}}</ref> The much favored food in Agattu was the [[ancient murrelet]] (''Synthliboramphus antiquus''), at 68.4% of the biomass and 46% by number, while the secondary prey were followed numerically by smaller [[Leach's storm-petrel]]s (''Oceanodroma leucorhoa'') (20.8%) and [[Lapland longspur]]s (10%) and in biomass by smallish ducks, the [[green-winged teal]] (''Anas carolinensis'') and [[harlequin duck]] (''Histrionicus histrionicus'') (13.4% biomass collectively).<ref name= Williams/> In the [[Murman Coast]] of Russia, also in the absence of lemmings, [[seabird]]s formed the largest part of the diet.<ref name= Krasnov>Krasnov, Y. (1985). ''To the biology of the Snowy Owl in the Eastern Murman. Birds of Prey and Owls in the Nature Reserves of the Russian Federation''. TSNIL GLAVOKHOTA, 110–116.</ref> ===Winter diet=== [[File:SnowyOwlAmericanBlackDuck.jpg|thumb|right|Snowy owl carries its kill, an [[American black duck]], [[Biddeford Pool, Maine]]]] On the wintering grounds, mammals often predominate in the snowy owl's food inland doing so less in coastal areas. Overall wintering snowy owls eat more diverse foods they do whilst breeding, furthermore coastal wintering snowy owls had more diverse diets than inland ones.<ref name= Holt/> As in summer, moderately sized [[water bird]]s such as [[Eurasian teal|teal]], [[northern pintail]] (''Anas acuta'') and numerous [[alcid]]s and the like are often focused on when hunting birds.<ref>{{cite journal|author1=Stronach, P. |author2= Cooper, J. |year=2010|title=Snowy Owl pellet containing Eurasian Teal|journal= British Birds|volume= 103|issue=6|pages= 360–361}}</ref><ref>{{cite journal|author=1Valenziano, R. L.|author2= Labedz, T. E. |year=2014|title=Stomach Content Analysis of Recent Snowy Owl (''Bubo scandiacus'') Specimens from Nebraska|url=https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=2354&context=nebbirdrev|journal= Neb. Bird Review|volume= 80 |issue=3|pages= 122–127}}</ref><ref>{{cite journal|title=Forensic techniques identify the first record of Snowy Owl (''Bubo scandiacus'') feeding on a Razorbill (''Alca torda'')|doi=10.1676/14-176.1}}</ref><ref>{{cite journal|doi=10.1111/jav.01257}}</ref> The diet in 62 pellets, amongst at least 75 prey items, from coastal [[Oregon]] showed the main foods as [[black rat]] (''Rattus rattus'') (at an estimated 40%), [[red phalarope]] (''Phalaropus fulicarius'') (31%) and [[bufflehead]] (''Bucephala albeola'') (19%). Witnessed attacks were mostly upon buffleheads in Oregon.<ref name= Patterson>Patterson, J. M. (2007). ''An analysis of Snowy Owl (Bubo scandiacus) diet during the 2005 to 2006 irruption along the Oregon and Washington coasts''. Northwestern Naturalist, 88(1), 12–15.</ref> In coastal southwestern [[British Columbia]], the diet among 139 prey items was 100% avian. The predominant prey were [[water bird]]s, mostly snatched directly from surface of the water and largely weighing {{convert|400|to|800|g|lb|abbr=on}}, i.e. buffleheads (at 24% by number and 17.4% by biomass of foods) and [[horned grebe]]s (''Podiceps auritus'') (at 34.9% by number and 24.6% by biomass), followed by variously other water birds, often the slightly larger species of [[glaucous-winged gull]] (''Larus glaucescens'') and the [[American wigeon]] (''Mareca americana'').<ref>{{cite journal|doi=10.2307/3800714}}</ref> A different study of this area also showed the predominance of ducks and other water birds to wintering snowy owls here, although [[Townsend's vole]] (''Microtus townsendii'' ) (10.65%) and [[snowshoe hare]] (''Lepus americanus'') (5.7%) were also notably in a sample of 122 prey items.<ref name= Campbell>{{cite journal|author1=Campbell, R. W. |author2= Preston, M. I. |year=2009|title=Featured Species - Snowy Owl (''Bubo scandiacus'')|journal=Widllife Afield|volume= 6 |issue=2|pages= 173–255}}</ref> During winter, snowy owls consume more strongly nocturnal prey than lemmings such as ''[[Peromyscus]]'' mice and [[northern pocket gopher]]s (''Thomomys talpoides'').<ref name= Holt/><ref>{{cite journal|doi=10.29173/bluejay5360}}</ref> In southern Alberta, 248 prey items were found with [[North American deermouse]] (''Peromyscus maniculatus''), at 54.8% by number, and [[meadow vole]]s (''Microtus pennsylvanica''), at 27% by number, as the main foods of snowy owls over two years. Other prey in Alberta were [[grey partridge]] (''Perdix perdix'') (at 5.79% of total), [[White-tailed jackrabbit|jackrabbit]]s, [[weasel]]s and [[Short-eared owl|owls]]. [[Richardson's ground squirrel]]s (''Urocitellus richardsonii'') were consumed heavily in the Alberta study in a brief converged times of hibernation emergence and overwintering snowy owls.<ref name= Boxall2/> The sexual dimorphism in prey selection was also studied here, with male owls mainly focusing exclusively on the small rodents, females also took the same rodents but supplemented the diet with all alternate and larger prey.<ref name= Boxall2/> Overall, the meadow and [[montane vole]]s (''Microtus montanus'') constituted 99% of over 4500 prey items in Montana.<ref name= Detienne/> In [[Horicon Marsh]] in winter, 78% of the diet was meadow vole, with 14% being [[muskrat]]s (''Ondatra zibethicus''), 6% ducks and smaller balances of rats and other birds.<ref>{{cite journal|author=Keith, L. B. |year=1963|title=A note on Snowy Owl food habits|journal=The Wilson Bulletin|volume= 75|issue=3|pages= 276–277}}</ref> Snowy owls found in Michigan took meadow voles for 86% of the diet, [[white-footed mouse]] (''Peromyscus leucopus'') for 10.3% and [[northern short-tailed shrew]] (''Blarina brevicauda'') for 3.2%.<ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v092n01/p0116-p0120.pdf|author=Chamberlin, M. L. |year=1980|title=Winter hunting behavior of a snowy owl in Michigan|journal= The Wilson Bulletin|pages= 116–120|volume=92|issue=1}}</ref> Of 127 stomachs in New England in four irruptive winters from 1927 to 1942, of 155 prey items, 24.5% were [[brown rat]]s, 11.6% were meadow voles and 10.3% were [[dovekie]] (''Alle alle''), with a smaller balance of [[snowshoe hare]] and birds from snow buntings to [[American black duck]]s (''Anas rubripes''). During the same years, stomach contents in Ontario included 40 identified prey items, led by brown rats (20%), white-footed mice (17.5%) and meadow voles (15%); of 81 prey items from [[Pennsylvania]] in 60 stomachs that were not empty, [[eastern cottontail]] (''Sylvilagus floridanus'') (32%), meadow vole (11.1%), [[Chicken|domestic chicken]] (''Gallus gallus domesticus'') (11.1%) and [[northern bobwhite]] (''Colinus virginianus'') (5%) were the most often identified prey species.<ref name= Gross>{{cite journal|doi=10.2307/4079593|url=https://sora.unm.edu/sites/default/files/journals/auk/v061n01/p0001-p0018.pdf}}</ref> Introduced [[common pheasant]]s were found to be somewhat more vulnerable than native American gamebirds like [[ruffed grouse]] due to their tendency to crouch rather than flush when approached by a flighted predator like the snowy owl in a [[Glade (ecology)|glade]] or field.<ref name= Gross/> Some snowy owls wintering on [[Cliffed coast|rocky coasts]] and [[Jetty|jetties]] were known in New England to live almost entirely off of [[purple sandpiper]]s (''Calidris maritima'').<ref name= Gross/> The availability of brown rats may draw snowy owls to seemingly unattractive settings such as [[Landfill|garbage dump]]s and under bridges. Meanwhile, snowy owls wintering in [[Lowell, Massachusetts]] were seen to live largely off of [[rock dove]]s (''Columba livia'') caught off of buildings.<ref name= Gross/> Of 87 prey from stomachs in Maine, 35% were [[Rattus|rats]] or mice, 20% were snowshoe hares and 10% were passerines.<ref>{{cite journal|doi=10.2307/3795698}}</ref> A small study of 20 prey items in an irruptive winter in Kansas found that 35% of the prey were [[red-winged blackbird]] (''Agelaius phoeniceus''), 15% [[prairie vole]]s (''Microtus ochrogaster'') and 10% each by [[American coot]] (''Fulica americana'') and [[hispid cotton rat]]s (''Sigmodon hispidus'').<ref name= Young>{{cite journal|author=Young, E.A., Blake, C., Graham, R., Otte, C., Beckman, M. & Klem, D. |year=2014|title=Prey items from Snowy Owl (''Bubo scandiacus'') Pellets during the 2011–2012 Irruption in Kansas|journal=Kansas Ornithological Society|volume= 65 |issue=4|pages=33–40}}</ref> On the isle of [[St. Kilda, Scotland|St. Kilda]], 24 pellets were found for non-breeding snowy owls that stayed through the early summer. Of 46 prey items, the [[St Kilda field mouse]] (''Apodemus sylvaticus hirtensis'') was predominant by number at 69.6% but constituted 16.8% of biomass while adult [[Atlantic puffin]] (''Fratercula arctica'') constituted 63.5% of the prey biomass and 26% by number (rest of the balance being juvenile puffins and [[great skua]]s (''Stercorarius skua'')).<ref name= Miles>Miles, W. T. S., & Money, S. (2008). ''Behaviour and diet of non-breeding Snowy Owls on St Kilda''. Scottish Birds, 28, 11.</ref> The main subspecies of [[wood mouse]] was similarly dominant in the diet within [[County Mayo]], Ireland and were presumably snatched at night due to their strict [[nocturnality]].<ref>{{cite journal|author1=Murrey, T. |author2= Sleeman, D. |year=2005|title=Dietary analysis from the Snowy Owls pellets ''Nyctea scandiaca'' Linnaeus 1958, from the Mullet Peninsula, Co, Mayo|journal= Irish Naturalists' Journal|volume= 283|pages= 136}}</ref> In [[Knockando, Moray|Knockando]], the winter diet was led by [[European rabbit]]s (40.1%), [[red grouse]] (''Lagopus lagopus scotica'') (26.4%) and adult [[mountain hare]] (''Lepus timidus'') (20.9%) (in 156 pellets); in [[Ben Macdui]], the diet was led by rock ptarmigan (72.3%), [[field vole]]s (''Microtus agrestis'') and juvenile mountain hare (8.5%) (33 pellets); in [[Cabrach]], the diet was led by red grouse (40%), mountain hare (20%) and European rabbit (15%) (16 pellets).<ref name= Savory>{{cite journal|url=https://www.researchgate.net/publication/336837560_Unpublished_information_in_the_SOC_Archive_on_Snowy_Owl_diet_at_three_locations_in_Moray_in_the_1960s_Unpublished_information_in_the_SOC_Archive_on_Snowy_Owl_diet_at_three_locations_in_Moray_in_the_19|author=Savory, J. |year=2019|title=Unpublished information in the SOC Archive on Snowy Owl diet at three locations in Moray in the 1960s|journal= Scottish Birds|volume= 202|issue=204|pages= 202}}</ref> Among 110 prey items found for snowy owls found wintering during irruption in southern Finland, all but 1 prey item were field voles (the only other prey being a single [[long-tailed duck]] (''Clangula hyemalis'')).<ref name= Hakala/> Far to the east, wintering owls in the [[Irkutsky District]] were found to subsist mostly on [[narrow-headed vole]]s (''Microtus gregalis'').<ref name= Maleev>Maleev, V.G. & Popov, V. V. (2007). ''Birds of forest-steppes of the Upper Angara river basin''. Irkutsk.</ref> In a wintering population in Kurgaldga Nature Reserve of Kazakhstan, the main foods were [[grey red-backed vole]]s at 47.4%, [[winter white dwarf hamster]] (''Phodopus sungorus'') at 18.4%, [[steppe pika]] (''Ochotona pusilla'') at 7.9%, muskrat at 7.9%, [[Eurasian skylark]] (''Alauda arvensis'') at 7.9%, [[grey partridge]] at 5.3%, and both [[steppe polecat]] (''Mustela eversmanii'') and [[yellowhammer]] (''Emberiza citrinella'') at 2.6%<ref>Mosalev, A. (1969). ''About wintering of Snowy Owl in the Kurgaldga Nature Reserve''.</ref> On the [[Kuril Islands]], wintering snowy owls main foods were reported as tundra voles, brown rats, ermines and whimbrel, in roughly that order.<ref name= Potapov/> Data from the [[Logan Airport]] in over 6,000 pellets shows that meadow vole and brown rat predominated the diet in the area, supplanted by assorted birds both small and large.<ref name= Holt/><ref name= Smith/> [[American black duck]]s were primarily taken among bird species with other birds taken here including relatively large and diverse species [[Canada geese]] (''Branta canadensis''), brants, [[American herring gull]]s (''Larus argentatus''), [[double-crested cormorant]] (''Phalacrocorax auritus''), [[great blue heron]] (''Ardea herodias''), in addition to some formidable mammals such as [[Cat|house cat]], [[American mink]] (''Mustela vision''), and [[striped skunk]] (''Mephitis mephitis'').<ref name= Holt/><ref name= Smith/> Given the large size of some of this prey, it can be projected that the snowy owl can kill adult prey of around twice their own weight (i.e. geese, cats, skunks, etc.).<ref name= Holt/><ref name= Smith/> Other large prey is sometimes taken by snowy owls, all roughly within the {{convert|2|to|5|kg|lb|abbr=on}} weight range often include adults of large [[leporid]]s such as [[Arctic hare]] (''Lepus arcticus''),<ref name= Holt/> [[Alaskan hare]] (''Lepus othus''),<ref>Best, T. L., & Henry, T. H. (1994). ''Lepus othus''. Mammalian Species, (458), 1–5.</ref> [[mountain hare]]<ref>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V54/V54_N08/V54_N08_P307_320_A051.pdf|author=Bergman, G. |year=1961|title=The food of birds of prey and owls in Fenno-Scandia|journal= British Birds|volume= 54|issue=8|pages= 307–320}}</ref> and [[white-tailed jackrabbit]]s (''Lepus townsendii'').<ref name= Boxall2/> As well as several species of geese, probable cygnets of [[Tundra swan|Bewick's swan]]s (''Cygnus columbianus bewickii'')<ref>Nagy, S., Petkov, N., Rees, E., Solokha, A., Hilton, G., Beekman, J., & Nolet, B. (2012). [https://www.unep-aewa.org/en/publication/international-single-species-action-plan-conservation-northwest-european-population International single species action plan for the conservation of the northwest European population of Bewick's Swan (''Cygnus columbianus bewickii'')]. Wetlands International and The Wildfowl & Wetlands Trust (WWT), AEWA Technical Series, (44).</ref> as well as adults of the following: [[western capercaillie]] (''Tetrao urogallus'') (of both sexes),<ref>Gilyazov, A. V. (2005). ''Snowy Owl Nyctea scandiaca Linnaeus, 1758''. Red-data Book of the Murmansk Region. Murmansk: Murmansk book publishers: 316—318. [in Russian].</ref> [[greater sage-grouse]] (''Centrocercus urophasianus'')<ref>{{cite journal|doi=10.1002/jwmg.21168}}</ref> and [[yellow-billed loon]]s (''Gavia adamsii'').<ref>Uher-Koch, B. D., M. R. North, and J. A. Schmutz (2020). Yellow-billed Loon (''Gavia adamsii''), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.</ref> At the other end of the scale, the snowy owl has been known to take birds down to size of {{convert|19.5|g|oz|abbr=on}} [[dark-eyed junco]]s (''Junco hyemalis'') and mammals down the size of {{convert|8.1|g|oz|abbr=on}} [[common shrew]]s (''Sorex araneus'').<ref name= Hakala/><ref name= Young/><ref name= CRC1>Dunning, Jr., J. B. (1993). ''CRC handbook of avian body masses''. CRC Press, Boca Raton, FL.</ref> Fish are rarely taken anywhere but the snowy owl has been known to prey upon [[Arctic char]] (''Salvelinus alpinus'') and [[lake trout]] (''Salvelinus namaycush'').<ref name= Voous/><ref name= Gross/><ref name= Bailey>Bailey, A. M. (1948). ''Birds of Arctic Alaska''. Colorado Mus. Nat. Hist., Popular Ser., 8.</ref> ===Interspecific predatory relationships=== [[File:Snowy owl and peregrine falcon.webm|thumb|left|A waterlogged snowy owl in winter victim to the very swift [[Mobbing (animal behavior)|mobbing]] of a [[peregrine falcon]].]] The snowy owl is in many ways a very unique owl and differs from other species of owl in its [[ecological niche]].<ref name= Voous/><ref name= Johnsgard/> Only one other owl, the [[short-eared owl]], is known to breed in the High Arctic.<ref name= Voous/> However, the snowy owl shares its primary prey, the [[True lemming|brown]] and [[collared lemming]]s, with a number of other avian predators. In sometimes differing parts of the Arctic, competing predators for lemmings are, in addition to short-eared owls, [[pomarine jaeger]]s (''Stercorarius pomarinus''), [[long-tailed jaeger]]s (''Stercorarius longicaudus''), [[rough-legged buzzard]]s (''Buteo lagopus''), [[hen harrier]]s (''Circus cyaenus''), [[northern harrier]]s (''Circus hudsonius'') and generally less specialized [[gyrfalcon]]s (''Falco rusticollis''), [[peregrine falcon]]s (''Falco peregrinus''), [[glaucous gull]]s (''Larus hypoboreus'') and [[common raven]]s (''Corvus corax''). Certain carnivorous mammals, especially the [[Arctic fox]] and, in this region, the [[Stoat|ermine]], are also specialized to hunt lemmings.<ref name= Voous/><ref name= Pitelka/><ref>{{cite journal|doi=10.2307/3545963}}</ref><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v082n02/p0130-p0157.pdf|author=Maher, W. J. |year=1970|title=The Pomarine Jaeger as a Brown Lemming predator in northern Alaska|journal= Wilson Bulletin|volume= 82|pages= 130–157}}</ref> Most of the lemming predators are intolerant of the competition given the scattered nature of lemming populations and will displace and/or kill one another given the chance. However, given the need to conserve energy in the extreme environment, the predators may react passively to one another.<ref>{{cite journal|jstor=4314894|author=Wiklund, C. G., Angerbjörn, A., Isakson, E., Kjellén, N., & Tannerfeldt, M. |year=1999|title=Lemming predators on the Siberian tundra|journal=Ambio|volume= 281–286}}</ref><ref name="Gilg" /> When unusually breeding south in the Subarctic such as western Alaska, Scandinavia and central Russia, the number of predators with which the snowy owls are obligated to share prey and compete with may be too numerous to name.<ref name= Potapov/> The taking of the young and eggs of snowy owls has been committed by a large number of predators: [[Buteo|hawks]] and [[eagle]]s, the northern [[Skua|jaeger]]s, peregrine and gyrfalcons, glaucous gulls, common ravens, [[Arctic wolf|Arctic wolves]] (''Canis lupus arctos''), [[polar bear]]s, [[brown bear]]s (''Ursus arctos''), [[wolverine]]s (''Gulo gulo'') and perhaps especially the Arctic fox.<ref name= Holt/><ref name= Taylor/><ref>Ovsyanikov, N.G. & Menushina, I.E. (1986). ''[Competition for food between the Snowy Owl (Nyctea scandiaca) and the arctic fox (Alopex lagopus)]''. Zoologischeskii Zhurnal. 65(6): 901–910. In Russian with English summary.</ref> Adult snowy owls on the breeding grounds are far less vulnerable and can be justifiably qualified as an [[apex predator]].<ref name= Konig/><ref name= Voous/> Instances of killing of adult snowy owls on the breeding grounds have been witnessed to be committed by a pair of [[pomarine jaeger]]s on an incubating adult female snowy owl (possibly merely a competitive attack as she was left uneaten) and by an Arctic fox that killed an adult male snowy owl.<ref name= Bailey/><ref>Menyushina, I. E. (1994). "Interspecies relation of the polar fox (''Alopex lagopus'' L.) and the Snowy Owl (''Nyctea scandiaca'' L.) during the breeding season in the Wrangel Island. 1". Lutreola 3: 15–21.</ref> [[File:Die Raubvögel Deutschlands und des angrenzenden Mitteleuropas (Pl. L) (21138120888).jpg|thumb|An early illustration showing snowy owl predation upon a [[gyrfalcon]].]] When it goes south to winter outside of the Arctic, the snowy owl has a potential to interact with a number of additional predators.<ref name= Voous/> By necessity, it shares its wintertime diverse prey with a number of formidable predators.<ref name= Voous/><ref name= Holt/> These are known to include their cousins, the [[great horned owl]] and the [[Eurasian eagle-owl]]. They are relieved of heavy competition from the related species by differing temporal activity, i.e. being more likely to actively hunt in daytime, and by habitat, using rather more open (quite often nearly treeless) habitats than them.<ref name= Potapov/><ref name= Voous/> During a study of wintering snowy owls in [[Saskatchewan]], the authors indicated that the snowy owls may avoid areas inhabited and defended by great horned owls. Although they usually occurred here outside of a {{convert|800|m|ft|abbr=on}} radius of central great horned owl ranges, they did not avoid the {{convert|1600|m|ft|abbr=on}} radius and different habitat usage may be a dictating factor.<ref name= Chang2>Chang, A. M. (2017). ''Habitat use, movement patterns, and body condition of male and female Snowy Owls (Bubo scandiacus) in winter'' (Doctoral dissertation, University of Saskatchewan).</ref> Given their mildly slighter size, it is unlikely that great horned owls (unlike the larger eagle-owl) would regularly dominate snowy owls in interactions and either species may give way to other depending on the size and disposition of the owls involved.<ref name= Potapov/><ref name= Voous/> Little study has been undertaken into the [[Trophic level|trophic competition]] of snowy owls with other predators during winter and, due to their scarcity, few predators are likely to expel much energy on competitive interactions with them, although many other predators will engage in anti-predator [[Mobbing (animal behavior)|mobbing]] of snowy owls.<ref name= Voous/><ref name= Holt/> Largely in winter, snowy owls have been the victim of a number of larger avian predators, though attacks are likely to be singular and rare.<ref name= Voous/><ref name= Holt/> Instances of predation on snowy owls are known to have been committed several times in winter only by [[Eurasian eagle-owl]]s.<ref name= Mikkola3>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V69/V69_N04/V69_N04_P144_154_A030.pdf|author=Mikkola, H. |year=1976|title=Owls killing and killed by other owls and raptors in Europe|journal= British Birds|volume= 69|pages= 144–154}}</ref> Additionally, [[golden eagle]]s (''Aquila chrysaetos'') have been known to prey on snowy owls as well as all northern [[sea eagle]]s: the [[Bald eagle|bald]] (''Haliaeetus leucocephalus''), [[White-tailed eagle|white-tailed]] (''Haliaeetus albicilla'') and [[Steller's sea eagle]]s (''Haliaeetus pelagicus'').<ref name= Holt/><ref name= Campbell/><ref>{{cite journal|author=Johnson, M.J. |year=1995|title=Bald Eagle predation on Snowy Owl|journal= Loon|volume= 67|issue=2|pages=107}}</ref> Snowy owls are also sometimes killed by birds that are mobbing them. In one instance, a [[peregrine falcon]] killed a snowy owl in a stoop after the owl had itself killed a fledgling falcon.<ref name= Bent/><ref name= Bailey/><ref>Nelson, E. W. (1887). ''Birds of Alaska'', p. 35-222. In H. W. Henshaw [ed.], Report upon natural history collections made in Alaska between the years 1877 and 188 1. No. III Arctic Series, Signal Service, U.S. Army, Government Printing Office,-Washington, DC.</ref> Anecdotal report indicate predation by [[gyrfalcon]]s (on snowy owls of unknown age and condition) but it was possibly also an act of mobbing.<ref name= Heggoy>Heggøy, O., & Øien, I. J. (2014). ''Conservation status of birds of prey and owls in Norway''. NOF/BirdLife Norway-Report, 1, 1–129.</ref> In another, a huge [[Flock (birds)|throng]] of [[Arctic tern]]s (''Sterna paradisaea'') relentlessly swarmed and attacked a snowy owl until it meet its demise.<ref>Meinertzhagen, R. (1959). ''Pirates and Predators: The piratical and predatory habits of birds''. Oliver & Boyd.</ref> Almost certainly more often than being victim of other predators, snowy owls are known to dominate, kill and feed on a large diversity of other predators.<ref name= Voous/><ref name= Mikkola3/> Snowy owls, much like other ''Bubo'' owls, will opportunistically kill other birds of prey and predators. Although they will readily plunder the nests of other raptorial birds given the opportunity, most predations are on full-grown raptorial birds during winter due to the scarcity of raptor nests in the open tundra.<ref name= Voous/> In addition, most competing predators of the Arctic, excepting the very large mammals, are probably vulnerable to a hungry snowy owl.<ref name= Voous/><ref name= Holt/> In data from the [[Logan Airport]] alone over different winters, the snowy owls were observed to have preyed upon an impressive diversity of other raptorial birds: [[rough-legged buzzard]]s, [[American kestrel]]s (''Falco sparverius''), [[peregrine falcon]]s, [[barn owl]]s, other snowy owls, [[barred owl]]s (''Strix varia''), [[northern saw-whet owl]]s (''Aegolius acadicus'') and [[short-eared owl]]s. While owls are likely encountered during corresponding hunting times, it is likely that the swift falcons are usually ambushed at night (much as other ''Bubo'' owls will do).<ref name= Holt/><ref name= Smith/> In both the tundra and the wintering ground, there are several accounts of predation by snowy owls on short-eared owls.<ref name= Potapov/><ref name= Mikkola3/><ref>{{cite journal|doi=10.2307/1368028}}</ref> In addition, snowy owls have been known to prey on [[northern harrier]]s,<ref name= Holt/><ref name= Smith/> [[northern goshawk]]s (''Accipiter gentilis'')<ref name= Voous/> and [[gyrfalcon]]s.<ref name= Voous/><ref name= Mikkola3/> In a few cases, both juvenile and adult [[Arctic fox]]es have been known to fall prey to snowy owls.<ref name= Parker/><ref name= Stenkewitz/><ref name= Krechmar/><ref name="Gilg">{{cite journal|doi=10.1111/j.2006.0030-1299.14125.x}}</ref><ref>{{cite journal|title=''Alopex lagopus''|doi=10.1644/0.713.1}}</ref> A wintering snowy owl in [[Saskatchewan]] was observed to have preyed on an adult [[red fox]] (''Vulpes vulpes''). Predation by snowy owls on red foxes was also reported in the [[Irkutsky District]] of Russia. With an adult weight around {{convert|6|kg|lb|abbr=on}} (and far from defenseless), red fox may be the largest known prey known for snowy owls.<ref name= Maleev/><ref>{{cite journal|doi=10.29173/bluejay3979}}</ref> Besides aforementioned predation on domestic cats and skunks, several members of the [[weasel]] family, both small and relatively large, are known to be opportunistically hunted by snowy owls.<ref name= Potapov/><ref name= Voous/><ref name= Holt/><ref name= Smith/><ref name= Hakala/><ref>{{cite journal|doi=10.2307/3565424}}</ref> As a result of its potential predator status, the snowy owl is frequently mobbed at all times of the year by other predatory birds, including fierce dive-bombing by several of the northern falcons on the wintering grounds, including even by the relatively tiny but fierce and very agile [[Merlin (bird)|merlin]] (''Falco columbarius''). The much bulkier snowy owls cannot match the speed and flight ability of a falcon, ai may be almost relentlessly tormented by some birds such as peregrines.<ref name= Voous/><ref name= Mikkola3/><ref>{{cite journal|doi=10.29173/bluejay208}}</ref> ==Breeding== ===Pair bond and breeding territory=== In Utqiaġvik, of 239 recorded breeding attempts, 232 were monogamous, the other 7 [[Bigamy|social bigamy]].<ref name= Holt/> On [[Baffin Island]], 1 male bred with 2 females and sired 11 total fledged young.<ref name= Watson/> Another case of bigamy was reported in Norway where the 2 females bred to one male were {{convert|1.3|km|mi|abbr=on}} apart in nest site location.<ref name= Hagen/> On Feltar from 1967 to 1975, a male breed with two females, 1 younger and was possibly his own [[Incest|daughter]]. In the Feltar males first time breeding with both females, he did not bring food to the younger female. However, when older female disappeared the following year, the male and younger female producing 4 young, but disappeared the subsequent year altogether in 1975.<ref name= Robinson/> There are also unconfirmed cases of [[polyandry]], with 1 female being fed by 2 males. Snowy owls can breed once per year but when food is scarce many do not even attempt to breed.<ref name= Konig/><ref name= Voous/> Despite frequent wandering in search of food, they generally adhere more so than to a strict breeding season than [[short-eared owl]]s nesting in the tundra.<ref name= Voous/> 9 radio-tagged female snowy owls about [[Bylot Island]] were tracked to study how pre-laying snow cover effects their searching behavior for breeding area. These tracked females searched an average of 36 days and covered an average of {{convert|1251|km|mi|abbr=on}}. It is thought that the male and female mutually find an attractive breeding spot independently and converge.<ref>{{cite journal|doi=10.1186/s40462-015-0028-7}}</ref> The breeding territory normally averages about {{convert|2.6|km2|sqmi|abbr=on}} as in both [[Baffin Island]] and [[Ellesmere Island]] but varies in accordance to abundance of food and density of owls.<ref name= Konig/><ref name= Watson/><ref name= MacDonald/> Nesting territories average at Baffin island in the range of {{convert|8|to|10|km2|sqmi|abbr=on}} during poor lemming years.<ref name= Watson/> Nesting territories may up to {{convert|22|km2|sqmi|abbr=on}} on [[Southampton Island]] and had a mean distance of {{convert|4.5|km|mi|abbr=on}} between active nests.<ref name= Sutton1/> In Utqiaġvik, nesting pairs can vary from none to at least 7 and the territories average {{convert|5|to|10|km2|sqmi|abbr=on}}, with mean nest distances of {{convert|1.5|to|6|km|mi|abbr=on}}.<ref name= Pitelka/> In the Norwegian highlands, nesting occurs only at times of plenty distances of {{convert|1.2|to|3.7|km|mi|abbr=on}} between nests, averaging {{convert|2.1|km|mi|abbr=on}}.<ref name= Hagen/> Males marks territory with singing and display flights and likely always initiates.<ref name= Watson/> During the display, he engages in exaggerated wing beats with a shallow undulating and bouncy courtship flight with wings held in a [[Dihedral (aeronautics)|dihedral]]. He often drops to the ground but then flies again to only glide gently back down. Overall, the flight is somewhat reminiscent of the flight of a [[moth]].<ref name= Watson/><ref name= Pitelka/><ref name= Tulloch/><ref name= Robinson/> Females will answer her mate with her song during courtship.<ref name= Konig/> While courting, the male often also carries a lemming in his bill, then bows with cocked tail, similarly as in related owls (seldom displaying some other prey like [[snow bunting]]s). He then flaps his wings open in an emphatic manner, with the ground display being relatively brief (about 5 minutes). The female may possibly refuse to breed if ritual not performed.<ref name= Watson/><ref name= Taylor/> A possible courtship was engaged in by a male in southern Saskatchewan when a female was sighted.<ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v094n01/p0079-p0081.pdf|author1=Boxall, P. C. |author2= Lein, M. R. |year=1982|title=Possible courtship behavior of Snowy Owls in winter|journal= Wilson Bulletin|volume= 94|pages=79–81}}</ref> On Southampton Island, at least 20 males observed in late May in a "lemming year".<ref name= Voous/><ref name= Sutton1/> Nesting territory defense displays, not highly different from courtship displays, includes undulating flight and stiffly raised wings with bouts of exaggerated, delayed wing beats, looking like enormous white moths exposing their white wings under the sun.<ref name= Taylor/> At times, competing males will interlock claws in mid-air.<ref name= Voous/> Territorial and nuptial displays are followed by a ground display by the male with the wings arched up in an "angel" posture, visible for well over a mile.<ref name= Voous/> ===Nest sites=== [[File:Tundra Polygons and Pingos (9514080830).jpg|thumb|left|Snowy owls often seek out polygons such as these in the [[tundra]].]] Most individuals arrive at the nest site by April or May with a few overwintering arctic exceptions.<ref name= Murie/><ref name= Marine/><ref name= Pitelka2/><ref name= Fuller/> Males advertises potential nest sites to his mate by scratching the ground and spreading his wings over it.<ref name= Konig/> The nest is usually a shallow depression on a windswept eminence in the open tundra. There seems to be a variety of qualifiers for appropriate nest sites. The nest site is typically snow-free and dry relative to the surrounding environment, usually with a good view of the surrounding landscape. The nest may be made of [[ridge]]s, [[Mound|elevated mound]]s, high [[polygon]]s, [[hummock]]s, hills, man-made mounds and occasionally [[Outcrop|rocky outcrops]]. If covered with vegetation, taller plants that may obstruct view are plucked away sometimes.<ref name= Konig/><ref name= Voous/><ref name= Watson/><ref name= Pitelka2/><ref name= Holt3>{{cite journal|doi=10.5253/078.097.0422}}</ref> The nest sites are often long-established and naturally created by the freeze-thaw process of the tundra.<ref name= Voous/><ref name= Holt/> [[Bar (river morphology)|Gravel bars]] may be used as well.<ref name= Potapov/> The female may take the most active role in the nest's condition of any owl species.<ref name= Holt/><ref name= Mikkola/> No owl build their own nests but female snowy owls take about three days constructing a scrape, digging with her claws and rotating until a fairly circular bowl is formed. She will still not construct or add foreign materials to the nest (despite some circumstantial evidence of moss and grass from outside the nest mound being found).<ref name= Holt/><ref name= Murie/><ref name= Tulloch/> In two separate cases in Utqiaġvik, two separate females dug out a second scrape to the side and below the main nests and appeared to have called all chicks to the more secluded nest to ride out severe weather until the skies cleared.<ref name= Holt/> The Utqiaġvik nest scrapes averaged {{convert|47.7|x|44|cm|in|abbr=on}} in 91 with a mean depth of {{convert|9.8|cm|in|abbr=on}} while the scrapes were smaller in [[Hooper Bay]], reportedly {{convert|25|to|33|cm|in|abbr=on}} diameter and {{convert|4|to|9|cm|in|abbr=on}} in depth.<ref name= Murie/><ref name= Holt3/> Occasionally, in the lower tundra, snowy owls may too use old nests of [[rough-legged buzzard]]s as well as abandoned [[eagle]] nests.<ref name= Voous/> Unlike other northerly breeding raptorial birds, the snowy owl is not known to nest on cliffs and the like, so do not enter into direct competition with eagles, falcons, ravens or other ''Bubo'' owls when nesting to the relative south.<ref name= Voous/> The area of nest mound often has a relatively rich plant life which attract the lemmings, which may tunnel right under and around the owl's nest.<ref name= Voous/> [[Goose|Geese]], ducks and [[shorebird]]s of several species known to gain incidental protection by nesting close to snowy owls. Conversely, the snowy owls will sometimes kill and eat both young and adults of these birds, which implies a trade-off in the benefits.<ref name= Parmelee/><ref name= Murie/><ref name= Robinson/><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v109n03/p0449-p0461.pdf|author=Tremblay, J. P., Gauthier, G., Lepage, D., & Desrochers, A. |year=1997|title=Factors affecting nesting success in greater snow geese: Effects of habitat and association with snowy owls|journal= The Wilson Bulletin|pages= 449–461|volume=109|issue=3|jstor=4163840}}</ref><ref>{{cite journal|doi=10.1139/z96-210}}</ref><ref>{{cite journal|doi=10.1007/BF02465456|title=How do Brent Geese (''Branta b. bernicla'') cope with evil}}</ref><ref>Smith, P. A. (2003). ''Factors affecting nest site selection and reproductive success of tundra nesting shorebirds'' (Doctoral dissertation, University of British Columbia).</ref> ===Eggs=== [[File:Eggs of British Birds Seebohm 1896 Plate6.jpg|thumb|An illustration of 8 European owl species' eggs, with the snowy owl in the middle of the right row. Note the much larger egg of the [[Eurasian eagle-owl]] at bottom.]] Egg-laying normally begins during early May to the first 10 days of June.<ref name= Konig/> Late thaws are harmful to them since they allow too little time for the full breeding process, with particularly importance given to good food supply in May for adults, even more so apparently than food supply in July when young are being fed.<ref name= Hume/> Late nests are possible cases of inexperienced pairs, low food supplies, bigamy or even replacement clutches.<ref name= Holt/><ref name= Watson/><ref name= Robinson/> The clutch is extremely variable in size averaging around 7–9, with up to 15 or 16 eggs recorded in extreme cases. The clutch size very large relative to related species.<ref name= Konig/><ref name= Voous/> Mean clutch sizes were 7.5 in a sample of 24 in Hooper Bay (range of 5–11); 6.7 in a sample of seven from Utqiaġvik (4–9); 9 in a sample of a sample of 5 in Baffin Island; 9.8 on Victoria Island; 8.4 (in a sample of 14) on Elsemere Island; 7.4 on Wrangel Island and 7.74 in Finnish Lapland.<ref name= Pitelka/><ref name= Watson/><ref name= Cramp/><ref name= Sutton/><ref name= Hart/> The average clutch size was 9.8 in a good year in [[Victoria Island (Canada)|Victoria Island]] while in a good year in Utqiaġvik the mean was 6.5.<ref name= Parmelee/><ref name= Pitelka/> The clutch is laid directly to the ground and are pure, glossy white.<ref name= Konig/><ref name= Holt/> An average egg is around {{convert|56.4|x|44.7|mm|in|abbr=on}} with a range of heights from {{convert|50|to|70.2|mm|in|abbr=on}} and diameter of {{convert|41|to|49.3|mm|in|abbr=on}}. Egg weights are around {{convert|47.5|to|68|g|oz|abbr=on}}, the median or average being {{convert|53|and|60.3|g|oz|abbr=on}} in different datasets.<ref name= Konig/><ref name= Watson/><ref name= Hagen/><ref>Baicich, P.J. & Harrison, C.J.O. (1997). ''A Guide to the Nests, Eggs, and Nestlings of North American Birds''. Academic Press, San Diego, California.</ref><ref>Schönwetter, M. (1960). ''Handbuch der Oologie'' (Ed. W. ME~SE). Vol. 1. Berlin.</ref> The average egg size is relatively small, about 20% smaller than Eurasian eagle-owl eggs and 8% smaller than great horned owl eggs.<ref name= Potapov/><ref name= Voous/><ref>Bendire, C. E. (1892). ''Life histories of North American birds with special reference to their breeding habits and eggs''. U.S. National Museum Special Bulletin 1.</ref> Laying intervals are normally 2 days (41–50 hours mostly).<ref name= Konig/><ref name= Schaanning>Schaanning, H. T. L. (1907). ''Østfinmarkens fuglefauna''. Bergens Mus. Arb. 8:1–98.</ref><ref>Pleske, T. (1928). ''Birds of the Eurasian tundra''. Mem. Boston Soc. Nat. Hist. 6:111–485.</ref> The laying intervals can range up to 3–5 days in inclement weather.<ref name= Voous/><ref>Parmelee, D. F., Stephens, H. A. & Schmidt, R. H. (1967). ''The birds of Southeastern Victoria Island and adjacent small islands''. National Museum of Canada Bulletin 222.</ref> The laying of a clutch of 11 eggs can take 20–30 days, while a more typical nest of around 8 takes about up to 16 days.<ref name= Voous/><ref name= Bent/> The interval between the 8th and 9th eggs can be up to about 4 days.<ref name= Robinson/> Incubation begins with the first egg and is by female alone, while she is fed by her mate.<ref name= Konig/> ===Parental behavior=== [[File:SnowyOwl2.jpg|thumb|left|A captive mother snowy owl with its chick.]] Food is brought to the nest by males and surplus food is stored nearby.<ref name= Konig/> Females in breeding season often develop a very extensive [[brood patch]] which in this species is a fairly enormous, high vascularized featherless area of pink belly skin.<ref name= Voous/><ref name= Parmelee/> Incubation lasts 31.8–33 days (unconfirmed and possibly dubious reports from as little as 27 to as much as 38-day incubations).<ref name= Konig/><ref name= Murie/><ref name= Robinson/><ref name= Schaanning/> The female alone broods the young, often while simultaneously incubating still unhatched eggs.<ref name= Konig/><ref name= Holt/> Sometimes older chicks incidentally brood their younger siblings and females may shelter the young under her wings during inclement weather.<ref name= Parmelee/><ref name= Watson/> When first feeding the young, the female may dismantle prey to feed the young only the softer body parts then gradually ramping up the size of proportions until they eat a whole prey item.<ref name= Watson/> Aggressive encounters with parent snowy owls are said to be "genuinely dangerous" and one resource claimed the snowy owl to be the bird species with the most formidable nest defense displays towards humans.<ref name= Voous/><ref name= Bent/><ref>Couzens, D. (2008). ''Extreme Birds: The World's Most Extraordinary and Bizarre Birds''. Firefly Books.</ref> The usual response to sighted humans near the nest is mild but continued approach begins to increasingly irritate the parents.<ref name= Holt/> At times, humans are forcefully dive-bombed upon, while other potential threats are dealt with in a “forward-threat” where the male walks towards the intruders, engaging in impressive feather-raising and fanning out of half-spread wings until they run forward and slash with both their feet and bill.<ref name= Voous/><ref name= Bent/><ref name= Watson/><ref name= Sutton1/><ref name= Parmelee/> Fairly serious injuries have been sustained in the worst of snowy owl defensive attacks, including cranial trauma, requiring researchers to make the long trek back to medical care, although human fatalities are not known.<ref name= Sutton/><ref>Barth, E. K. (1950). ''Efter fjallugglor pf Hardangervidda''. Fauna Flora, 45: 235–242.</ref> Snowy owl parents have been seen to aggressively attacked glaucous gulls, arctic fox and dogs in breeding ground in Utqiaġvik.<ref name= Holt/> Non-predatory animals like [[Reindeer|caribou]] in Utqiaġvik and sheep (''Ovis aries'') in Fetlar are attacked as well, possibly to avoid potential trampling of the eggs or the young.<ref name= Parmelee/><ref name= Tulloch/> Males are said to do the majority of nest defense but the female will also often become involved as well.<ref name= Holt/> Analysis showed in [[Lapland, Sweden]], that females in nest defense against people engaged in vocal displays (warning and mewing calls) and that males did not engage in mewing but did engage in most hooting calls, many warning calls and almost all physical attacks.<ref name= Wiklund>Wiklund, C. G., & Stigh, J. (1983). ''Nest defence and evolution of reversed sexual size dimorphism in Snowy Owls Nyctea scandiaca''. Ornis Scandinavica, 58–62.</ref> In other instances, [[distraction display]]s are engaged in against predators, with a "broken-wing act" including high, thin squeals interspersed with weird squeaks, often taking flight only to quickly fall from the sky and imitate a struggle.<ref name= Voous/><ref>[http://animaldiversity.ummz.umich.edu/site/accounts/information/Nyctea_scandiaca.html ADW: ''Nyctea scandiaca: Information'']. Animaldiversity.ummz.umich.edu. Retrieved on 19 October 2010.</ref> One author recorded a male to draw him about {{convert|2|km|mi|abbr=on}} from the nest before ceasing.<ref name= Parmelee/> 77% of 45 distraction displays in Lapland, Sweden were by females.<ref name= Wiklund/> ===Development of young=== [[File:Young snowy owls (69120).jpg|thumb|An old photo of snowy owl nestlings on [[Baffin Island]].]] Hatching intervals are generally from 1 to 3 days, quite often within 37–45 hours apart.<ref name= Watson/><ref name= Tulloch/> New chicks are [[Altriciality|semi-altricial]] (i.e. typically helpless and blind), initially being white and rather wet but dry by the end of the first day. The weight of 7 hatchlings was {{convert|35|to|55|g|oz|abbr=on}}, with an average of {{convert|46|g|oz|abbr=on}} while 3 were {{convert|44.7|g|oz|abbr=on}}.<ref name= Parmelee/><ref name= Watson/> Due to the pronounced asynchrony of the egg-laying and hatching, the size difference between siblings can be enormous and in some cases when the smallest chick weighs only {{convert|20|to|50|g|oz|abbr=on}}, the biggest chick already has attained a weight of around {{convert|350|to|380|g|oz|abbr=on}}.<ref name= Watson/><ref name= Barth/> When the oldest chick is about 3 weeks, the female will start to hunt as well as the male and both may directly feed the young although in some cases they may not need hunt very much if lemmings are particularly numerous.<ref name= Konig/><ref name= Voous/> [[Hoarding (animal behavior)|Caches]] of lemmings around a nest may include more than 80 lemmings that can support the family.<ref name= Voous/> Unlike many owls, the chicks of snowy owls are not known to behave aggressively toward one another or to engage in [[siblicide]], perhaps in part due to the need for energy conservance.<ref name= Holt/><ref name= Tulloch/> Some cases of [[cannibalism]] of chicks by the family group were thought to be cases where chicks die from other causes.<ref name= Sutton/> When they are about 2 weeks, the chicks may begin to walk around the nest site which they leave by 18–28 days, although they are still unable to fly and may find safety in nooks and crannies of vegetation and rocks usually only about {{convert|1|to|2|m|ft|abbr=on}} from the nest mound, as well as via their parents defense.<ref name= Konig/><ref name= Voous/><ref name= Romero>Romero, L. M., Holt, D. W. Maples M. & Wingfield, J. C.. (2006). ''Corticosterone is not correlated with nest departure in Snowy Owl chicks (Nyctea scandiaca)''. General and Comparative Endocrinology 149 (2): 119–123.</ref> Leaving the nest is thought to likely be an anti-predator strategy.<ref name= Holt/><ref>Holt, D. W. & Leasure, S. M. (1993). ''Short-eared Owl (Asio flammeus)''. In: ''The birds of North America, No. 62'', edited by A. Poole and F. Gill. Washington, DC: Acad. Nat. Sci., Philadelphia, PA; Am. Ornithol. Union.</ref> The male snowy owl may drop fresh prey deliveries directly on the ground near the wandering young.<ref name= Voous/> After about three weeks of age, the young may wander fairly widely, rarely to {{convert|1|km|mi|abbr=on}}, but usually stay within {{convert|500|m|ft|abbr=on}} of the nest mound.<ref name= Watson/><ref name= Tulloch/> Threat postures by young in reaction to researchers were first noticeable at about 20–25 days of age and common at about 28 days and the chicks can be impressively quick and agile-footed.<ref name= Holt/><ref name= Watson/> The first fledgling occurs at around 35–50 days, and by 50–60 days the young can fly well and hunt on their own.<ref name= Konig/><ref name= Voous/> The total care period is for 2–3.5 months, increasing in length with increased size of the brood.<ref name= Konig/><ref name= Parmelee/> Although independence was once thought to be sought by late August or early September but is more likely by late September to October when migration season for the species begins.<ref name= Holt/><ref name= Pitelka2/> The nesting cycle is similar in length to the Arctic short-eared owls and faster than Eurasian eagle-owls by up to 2 months.<ref name= Schrezinger>Schrezinger, W. (1974). ''Zur Ethologie und Jugendentwicklung der Schnee-Eule Nyctea scandiaca nach Beobachtungen in Gefangenschaft''. J. Orn, 115: 8–49.</ref> ===Maturity and nesting success=== [[File:SNOWY OWL, Canada.jpg|thumb|left|Snowy owl, juvenile, in Ontario, Canada.]] Sexual maturity reached the following year but the first breeding is normally at no sooner than the end of the second year of life.<ref name= Konig/> There is little strong evidence of typical age of first breeding but initial breeding by males could be inferred by the plumage of males in Utqiaġvik by plumage. At that stage, which the males were essentially all pure white, most were aged to about 3 to 4 years old.<ref name= Holt/> The snowy owl seems to markedly inconsistent in regard to breeding every year, often taking at least up to two years between attempts and sometimes as much as nearly a decade.<ref name= Potapov/><ref name= Fuller/> 7 satellite-marking females in Canada proved that they did breed in consecutive years, with 1 breeding over 3 consecutive years.<ref name= Therrien/> In 23 years at Utqiaġvik, snowys bred in 13 of them.<ref name= Holt/><ref name= Fuller/> Nesting success can reach 90–100% in even the largest clutches in high lemming years.<ref name= Voous/> While over the course of 21 years, 260 total nests were recorded in Utqiaġvik. There, from 4–54 nests were recorded annually. The Utqiaġvik nests bore 3 to 10 sized-clutches with a mean of 6 eggs per nest and an annual mean hatching success from 39 to 91%. 31–87% of chicks were able to depart on foot and 48–65% were annually estimated to survive to fledge; elsewhere, 40% survived to fledge.<ref name= Holt/><ref name= Parmelee/> In another set, 97% of observed eggs both hatched and fledged.<ref name= Watson/> In Norway, the fledging success from 10 nests was much lower at about 46%.<ref name= Hagen/> Norwegian data, which previously indicated it to be an almost accidental breeder in northern Norway, indicates that it is a more regular breeder than expected, though. 3 good years were found for snowy owls between 1968 and 2005: 1974 (when there were 12 pairs), 1978 (22 pairs) and 1985 (20 pairs), with 14 additional locations when potential (but not confirmed) breeding has occurred.<ref name= Jacobsen/> The main determinable causes of nest failure were deemed to be [[starvation]] and [[Hypothermia|exposure]].<ref name= Holt/> A number of Norwegian and Finnish nests were known to fail due to severe [[black fly]] parasitism.<ref>Solheim, R., Jacobsen, K. O., Øien, I. J., Aarvak, T., & Polojärvi, P. (2013). ''Snowy Owl nest failures caused by blackfly attacks on incubating females''. Ornis Norvegica, 36, 1–5.</ref> ==Longevity== The snowy owl can live a long life for a bird.<ref name= Holt/> Records show that the oldest snowy owls in captivity can live to 25 to even 30 years of age.<ref name= Konig/><ref name= Holt/><ref>Schenker, A. (1978). Höchsalter europaischer Vögel im Zoologischen Garten Basel. Ornithol. Beob. 75: 96–97.</ref> Typical lifespans probably reach around 10 years in the wild.<ref name= Konig/><ref name= Mikkola/> The longest known lifespan in the wild was one that initially banded (possibly in its first winter) in [[Massachusetts]] and recovered dead in [[Montana]] 23 years and 10-month later.<ref name= Holt/> The annual survival rate for twelve females on [[Bylot Island]] was estimated at around 85–92.3%.<ref>{{cite journal|doi=10.1002/jwmg.414}}</ref> It is often reputed that snowy owls frequently died from starvation, with historical accounts frequently opined they "had to" leave their breeding grounds due to lemming "crashes" but would starve to the south.<ref name= Kerlinger/><ref name= Gross1/><ref name= Zettenberg>{{cite journal|doi=10.1898/NWN07-19.1}}</ref> However, it was proven fairly early on that snowy owls often do survive throughout the winter.<ref name= Bent/> This is reinforced somewhat by small radio-tracking and banding studies of the northern [[Great Plains]] and the intermountain [[valley]]s of the northwestern United States.<ref name= Zettenberg/><ref name= Kerlinger3>{{cite journal|doi=10.2307/1368844}}</ref> More circumstance evidence shows a lack of starvation in the eastern part of North America as well.<ref>{{cite journal|title=Winter irruptive Snowy Owls (''Bubo scandiacus'') in North America are not starving|doi=10.1139/cjz-2017-0278|url=https://www.researchgate.net/publication/322843463_Winter_irruptive_snowy_owls_in_North_America_are_not_starving}}</ref> There is evidence that some adults are known to return to the same wintering areas in ensuing years, areas which are far south of their breeding range.<ref>{{cite journal|doi=10.29173/bluejay1721}}</ref><ref>{{cite journal|author1=Follen, D. |author2= Luepke, K. |year=1980|title= Snowy Owl recaptures|journal= Inland Bird Banding |volume=52|pages= 60}}</ref> At Logan Airport, most snowy owls that are seen appear to be in good condition.<ref name= Holt/><ref name= Smith/> Of 71 dead snowy owls found in winter in the northern Great Plains, 86% died from assorted [[Major trauma|traumas]], including [[Roadkill|collisions]] with automobiles and other, usually manmade, objects as well as [[electrocution]]s and [[Culling|shootings]]. Only 14% of the 71 deaths were due to apparent starving. Data showed some owls appeared to incur injuries but healed and survived.<ref name= Kerlinger3/> More evidence was found in wintering snowy owls in New York of [[Bone healing|healed fractures]], though some may require surgery to recover.<ref>{{cite journal|pmid=30204018|title=Successful Management of Open, Contaminated Metacarpal Fractures in an Adult Snowy Owl (''Bubo scandiacus'') With a Minimal Type II External Skeletal Fixator}}</ref> 537 wintering birds in Saskatchewan were studied based on [[Fatty acid metabolism|fat reserves]], which were superior in females over males and adults over juveniles; while 31% of females lacked fat reserves, at least 45% of males found starving or in a state of infirmity were males and 63% turned into [[Wildlife rehabilitation]] centres were also males.<ref name= Chang/> In British Columbia, of 177 snowy owl deaths, of owls to die, only a small percentage were due to natural causes, such as assumed starvation at 13% and 12% were "found dead".<ref name= Campbell/> 1 fledgling on Fetlar dead due to [[pneumonia]] and ''[[Staphylococcus]]'' while a second died from ''[[Aspergillosis]]''.<ref name= Robinson/> Evidence shows that in Utqiaġvik during exceptionally prolonged rains (i.e. 2 to 3 days), nest-departed young in Utqiaġvik were vulnerable to starvation, leading to [[hypothermia]] and pneumonia.<ref name= Holt/> Due to their natural history, the snowy owl may be effected more severely by [[Parasitism|blood parasitism]] than other raptors, due to lowered [[Immunity (medical)|immunity]].<ref>{{cite journal|pmid=29517448|title=Clinical effect of hemoparasite infections in snowy owls (''Bubo scandiacus'')}}</ref> Conversely, they appear to have lower levels of ectoparasites like [[Mallophaga|chewing lice]] than in other large owls per large samples from [[Manitoba]]. The snowy owls averaged about 3.9 chewing lice per host against 7.5 for great grey owls and 10.5 for great horned owls.<ref>{{cite journal|doi=10.4039/tce.2019.42|title=Infestation parameters for chewing lice (Phthiraptera: Amblycera, Ischnocera) infesting owls (Aves: Strigidae, Tytonidae) in Manitoba, Canada}}</ref> ==Status== This species presence and numbers is dependent on amount of food available. In "lemming years", snowy owls can appear to be quite abundant in habitat.<ref name= Konig/> Numbers of snowy owls are difficult to estimate even within studies that take place over decades due to the nomadic nature of adults.<ref name= Holt/> The population of [[Scandinavia]] has long been perceived as very small and [[Ephemerality|ephemeral]] with Finland holding 0–100 pairs; Norway holding 1–20 pairs and Sweden holding 1–50 pairs.<ref name= Holt/><ref name= Jacobsen/><ref>Väisänen, R. A., Lammi, E., & Koskimies, P. (1998). ''Distribution, numbers and population changes of Finnish breeding birds''. Otava, Helsinki, Finland.</ref><ref name= Saurola>{{cite journal|doi=10.5253/078.097.0411}}</ref> A low breeding population within [[European Russia]] has been estimated to hold 1,300–4,500 pairs and Greenland to have 500–1,000 pairs.<ref>BirdLife International (2015). ''European Red List of Birds''. Office for Official Publications of the European Communities, Luxembourg</ref><ref>{{cite journal|doi=10.3312/jyio.44.1|title=Cross-species amplification of microsatellite markers in the Great Horned Owl ''Bubo virginianus'', Short-eared Owl ''Asio flammeus'' and Snowy Owl ''B. scandiacus'' for use in population genetics, individual identification and parentage studies}}</ref> Other than northern part of the American continent, a majority of the snowy owl's breeding range is in northern Russia, but overall estimates are not known.<ref name= Holt/><ref>Stepanyan, L.S. (1990). ''Konspekt ornitologicheskoi fauny SSSR. [Conspectus of the Ornithological Fauna of the USSR]''. Nauka, Moscow. (In Russian with English summary.).</ref> An exact count of 4,871 individuals were seen on surveys between the [[Indigirka River|Indigirka]] and [[Kolyma river]]s.<ref name= Potapov/> The numbers estimated by Partners in Flight and other authors by the 2000s was that North America held about 72,500 snowy owls, about 30% of which were juveniles.<ref>Rich, T. D., Beardmore, C. J. Berlanga, H., Blancher, P. J., Bradstreet, M. S. W., Butcher, G. S., Demarest, D. W., Dunn, E. H., Hunter, W. C., Iñigo-Elias, E. E., Kennedy, J. A., Martell, A. M.. Panjabi, A. O., Pashley, D. N., Rosenberg, K. V., Rustay, C. M., Wendt, J. S. & Will, T. C. (2004). ''Partners in Flight North American Landbird Conservation Plan''. Cornell Lab of Ornithology, Ithaca, NY, USA.</ref><ref>{{cite journal|doi=10.2193/0091-7648(2006)34[1392:EOFHOW]2.0.CO;2}}</ref> The Canadian population of snowy owls was estimated at 10,000–30,000 (in the 1990s) or even to 50,000–100,000 individuals, perhaps improbably.<ref>{{cite journal|author=Kirk, D. A., Hussell D. & Dunn, E. |year=1995|title=Raptor population status and trends in Canada|journal= Bird Trends|volume= 4|pages= 2–9}}</ref><ref>Reding-License, A. A. (2015). Harfang des neiges (''Bubo scandiacus''). Government of Canada.</ref><ref>American Ornithologists' Union (1998). ''Check-list of North American Birds, 7th edition''. American Ornithologists' Union, Washington, DC, USA.</ref> Within Canada, the population on [[Banks Island]] was once claimed at up to 15,000–25,000 in productive years and in [[Queen Elizabeth Islands]] at about 932 individuals.<ref name= Manning/><ref>Miller, F. L. (1987). ''Snowy Owl numbers on twelve Queen Elizabeth Islands, Canadian High Arctic''. Journal of Raptor Research 21 (4): 153–157.</ref> Alaska is the only state with breeding snowy owls but has probably quite a bit fewer breeding owls than does Canada.<ref>Alaska Department of Fish and Game. State of Alaska special status species 2011.</ref> Furthermore, the Partners in Flight and the [[IUCN]] estimated that the world population was roughly 200,000–290,000 individuals as recently as the 2000s.<ref>PIFSC. ''Partners in Flight Science Committee (2013)''. Population estimates database (Version 2.0) 2013. Available from http://rmbo.org/pifpopestimates.</ref><ref>BirdLife International. ''Nyctea Scandiaca''. 2006 IUCN Red List of Threatened Species (2004). Available from http://www.iucnredlist.org.</ref><ref>Burton, J. A. (1973). ''Owls of the world''. New York: E. P. Dutton.</ref> However, in the 2010s, it has been discovered that all prior estimates were extremely excessive and that more precise numbers could be estimated with better surveying, [[Phylogeography|phylogeographic data]] and more insights into the owl's free-wheeling wanderings.<ref name="iucn status 19 November 2021" /><ref name= Holt/> It is now believed that there are only 14,000–28,000 mature breeding pairs of snowy owls in the world.<ref name= Holt/><ref name= Marthinsen/> During lemming declines, the number of nesting females may drop down to as low as 1,700 worldwide, a dangerously low number, and the number of snowy owls worldwide is less than 10% of what it was once thought to be.<ref name= Holt/><ref name= Marthinsen/><ref>{{cite journal|doi=10.2307/1527}}</ref> Due to the small and rapidly declining population, the snowy was uplisted in 2017 to being a [[vulnerable species]] by the [[IUCN]].<ref name="iucn status 19 November 2021" /> A 52% decline has been inferred for the North American population since the 1960s with another even more drastic estimate placing the decline from 1970 to 2014 at 64%.<ref>Berlanga, H., Kennedy, J. A., Rich, T. D., Arizmendi, M. C., Beardmore, C. J., Blancher, P. J., Butcher, G. S., Couturier, A. R., Dayer, A. A., Demarest, D. W., Easton, W. E., Gustafson, M., Iñigo-Elias, E., Krebs, E. A., Panjabi, A. O., Rodriguez Contreras, V., Rosenberg, K. V., Ruth, J. M., Santana Castellón, E., Vidal, R. Ma. & Will, T. (2010). ''Saving our shared birds: Partners in Flight tri-national vision for landbird conservation''. Ithaca: Cornell Laboratory of Ornithology.</ref><ref>Rosenberg, K. V., Blancher, P. J., Stanton, J. C., & Panjabi, A. O. (2017). ''Use of North American Breeding Bird Survey data in avian conservation assessments''. The Condor: Ornithological Applications, 119(3), 594–606.</ref> Trends are harder to delineate in Scandinavia but a similar downward trend is thought to be occurring.<ref name= Holt/><ref name= Jacobsen/><ref name= Saurola/> ===Anthropogenic mortality and persecution=== [[File:Snowy Owl, Gerald R. Ford Int&#039;l Airport, Grand Rapids, MI, 5 December 2013 (11230541096).jpg|thumb|left|Snowy owls often favor airports, such as this one at [[Gerald R. Ford International Airport]], in winter but the risk of [[birdstrike]] is high in such areas.]] Of 438 band encounters in the USG banding laboratory, almost all causes of death that could be determined, whether intentional or not, were correlated with human interference.<ref name= Holt/> 34.2% or 150 were dead due to unknown causes, 11.9% were shot, 7.1% were hit by automobiles, 5.5% were found dead or injured on highways, 3.9% were collision from towers or wires, 2.7% were in animal traps, 2.1% in airplane [[birdstrike]]s, 0.6% were [[Wire obstacle|entangled]] while the remaining 33.3% recovered injured due to assorted or unknown causes.<ref name= Holt/> Snowy owls are endangered by heavy airport usage resulting in [[birdstrike]]s. Many such collisions are known in Canada and likely also in [[Siberia]] and Mongolia .<ref name= Catling>{{cite journal|author=Catling, P. M. |year=1973|title=Food of snowy owls wintering in southern Ontario, with particular reference to the snowy owl hazard to aircraft|journal=Ontario field biol|volume= 7|pages= 41–45}}</ref><ref>{{cite journal|doi=10.2307/1367598}}</ref> Despite their danger to planes, no human fatalities have been recorded in collisions with this species.<ref>Blokpoel, H. (1976). ''Bird hazards to aircraft: problems and prevention of bird/aircraft collisions''. Clarke Irwin;[Ottawa]: Canadian Wildlife Service, Environment Canada: Pub. Centre, Supply and Services Canada.</ref> Snowy owls are always far outnumbered in Canadian airports in winter by [[short-eared owl]]s.<ref name= Voous/> However, relative to its scarcity, the snowy accounts for a very large balance of the birdstrikes recorded at American airports due to the attractiveness of the habitat, accounting for 4.6% of 2456 recorded collisions (the barn owl is the most frequently involved in birdstrikes).<ref name= Linnell>{{cite journal|doi=10.3356/JRR-17-64.1}}</ref> The species is locally vulnerable to [[pesticide]]s.<ref name= Konig/> The placement of buildings in the Utqiaġvik is now thought to have displaced some snowy owls.<ref name= Holt3/> In Norway, potential sources of disturbance near the nests include tourism, [[recreation]], [[Reindeer herding|reindeer husbandry]], [[Traffic|motorized traffic]], dogs, photographers, ornithologists and scientists.<ref name= Heggoy/> Some biologist have expressed concern that [[Telemetry|radio-tagging]] of snowy owls may cause some unclear detrimental effect on snowy owls but little evidence is known if they actually make the owls more susceptible to death.<ref>{{cite journal|doi=10.15845/on.v40i0.1309|title=Effects of satellite transmitters on survival in Snowy Owls ''Bubo scandiacus''}}</ref> Snowy owls can be quite wary, as they are not infrequently hunted by [[Circumpolar peoples]].<ref name= Voous/> Historically, the snowy owl was one of the most persecuted owl species.<ref name= Holt/> In the irruption of 1876–77, an estimated 500 snowy owls were shot, with similar numbers in 1889–90 and an estimated 500–1,000 killed in [[Ontario]] alone during 1901–02 invasion and about 800 killed in the 1905–06 invasion.<ref name= Bent/> Indigenous people of the Arctic historically killed snowy owls as food but now many communities in northern Alaska are fairly modernized, therefore biologists feel that the permitted killing of snowy owls by the indigenous is outdated.<ref name= Holt/><ref>{{cite journal|url=https://brooklynworks.brooklaw.edu/bjil/vol30/iss2/6/|author=Bakalar, E. M. |year=2004|title=Subsistence Whaling in the Native Village of Barrow: Bringing Autonomy to Native Alaskans Outside the International Whaling Commission|journal= Brook. J. Int'l L.|volume= 30|pages= 601}}</ref> The consumption of snowy owls by humans has been proven as far back as ancient cave deposits in France and elsewhere, and they have even been considered as one of the most frequent food species for early humans.<ref>{{cite journal|url=https://www.researchgate.net/publication/285483173_La_chasse_aux_oiseaux_pendant_la_Prehistoire|author=Mourer-Chauviré, C. |year=1979|title=La chasse aux oiseaux pendant la Préhistoire|journal= La Recherche|volume= 106|issue=10|pages= 1202–1210}}</ref><ref>{{cite journal|doi=10.1016/J.QUAINT.2015.11.146|title=Hunting fast-moving, low-turnover small game: The status of the snowy owl (''Bubo scandiacus'') in the Magdalenian}}</ref> They do not shun developed areas especially with old field that hold rodents and, due to lack of human experience, can be extremely tame and unable to escape armed humans.<ref name= Voous/> In British Columbia, of 177 snowy owl deaths, the most often diagnosed cause of death was shootings at 25%, often well after legal protection of the species.<ref name= Campbell/> The number [[Poaching|poached]] snowy owls in Ontario is opined to be unusually high considering their scarcity.<ref name= Desmarchelier>Desmarchelier, M., Santamaria-Bouvier, A., Fitzgérald, G., & Lair, S. (2010). ''Mortality and morbidity associated with gunshot in raptorial birds from the province of Quebec: 1986 to 2007''. The Canadian Veterinary Journal, 51(1), 70.</ref> While the species was once otherwise killed as food and then later shot out of resentment for perceived threats against domestic and favored game stock, the reasoning behind ongoing shooting of snowy owls into the 21st century is not well-understood.<ref name= Holt/><ref name= Dufresne/><ref name= Desmarchelier/> Siberian snowy owls are frequently victim to [[Bait (luring substance)|baited]] [[Trapping|fox traps]], with possibly up to around 300 killed in a year based upon very rough estimates.<ref>{{cite journal|author=Ellis, D. H. & D. G. Smith|year=1993|title=Preliminary report of extensive Gyrfalcon and Snowy Owl mortality in northern Siberia|journal= Raptor-Link |volume=1 |issue=2|pages=3–4}}</ref> [[Warfarin]] poisoning in use as [[rodenticide]]s are known to kill some wintering snowy owls, including up to six at Logan Airport alone.<ref name= Campbell/><ref name= Smith/><ref>{{cite journal|author=Stone, W. B., Okoniewski, J. C. & Stedelin, J. R. |year=1999|pmid=10231745|title=Poisoning of wildlife with anticoagulant rodenticides in New York|journal= Journal of Wildlife Diseases |volume=35|pages=187–193}}</ref> [[Mercury (element)|Mercury]] concentrations, most likely through [[bioaccumulation]], have been detected in snowy owls in the [[Aleutian Islands]] but it is not known whether fatal [[mercury poisoning]] has occurred.<ref>{{cite journal|doi=10.1016/j.marpolbul.2014.02.034}}</ref> [[Polychlorinated biphenyl|PCB]]s may have killed some snowy owls in concentration.<ref name= Heggoy/> Some airports have advocated and instituted the practice of shooting owls to avoid birdstrikes but successful [[Wildlife translocation|translocation]] is possible and preferred given the species protected status.<ref name= Holt/><ref name= Smith/><ref name= Linnell/> [[File:Stare Down Snowy (94026869).jpeg|thumb|right|A potential high risk of electrocution exists for snowy owls in winter.]] [[Global warming|Climate change]] is now widely perceived to perhaps the primary driver of the snowy owl's decline. As temperatures continue to rise, abiotic factors such as increased rain and reduced snow are likely to effect lemming populations and, in turn, snowy owls. These and potentially many other issues (possibly including modifying migrating behavior, vegetation composition, increased insect, disease and parasite activities, risk of [[hyperthermia]]) are a matter of concern.<ref name="iucn status 19 November 2021" /><ref name= Holt/><ref name= Heggoy/><ref name= ACIA>ACIA. (2004). ''Impacts of a warming climate: Arctic climate impact assessment''. Cambridge: Cambridge University Press.</ref><ref>Inouye, D. W. (2019). "Climate change in other taxa". ''Effects of Climate Change on Birds'', p. 257. {{ISBN|9780198824268}}</ref> Additionally, reduction of sea ice, which snowy owls are now known to rely extensively on, as a result of warming climates, impacts could be significant.<ref name="iucn status 19 November 2021" /><ref name= Holt/><ref name= Marine/> The effect of [[climate change]] was essentially confirmed in northern Greenland where a perhaps irrevocable collapse of the lemming population was observed. From 1998 to 2000, the lemming numbers appeared to have quickly declined. The number of lemmings per hectare (ha) is less than one-fifth of what it once was in Greenland (i.e. from 12 lemmings per ha to less than 2 per ha at peak). This is almost certainly correlated with a 98% decline in owl productivity as well as that of the local [[Stoat|stoats]] (the [[long-tailed jaeger]] and [[Arctic fox]]es, though previously thought to be almost as reliant on lemmings, seem to be more loosely coupled and more generalized and did not decline as much).<ref name= Schmidt>{{cite journal|pmid=22977153}}</ref><ref>{{cite journal|doi=10.4080/gpcw.2011.0113}}</ref> The amount of lemming mounds is much less than it once in northern Greenland and any variety of [[population cycle]] has been apparently abandoned by what remains of the lemmings.<ref name= Schmidt/> ==In popular culture== * The ''[[Harry Potter]]'' books by [[J. K. Rowling]], and subsequent [[Harry Potter (film series)|films]] of the same name, feature a female snowy owl named [[Magical creatures in Harry Potter#Hedwig|Hedwig]].<ref>{{cite web |url=https://www.pottermore.com/features/4-reasons-hedwig-was-better-than-everyone-else-at-hogwarts |title=4 reasons Hedwig was better than everyone else at Hogwarts |publisher=Pottermore |access-date=13 February 2018}}</ref> Concern was expressed by some in the media that the popularity of the Harry Potter films would cause an increase in the [[Black market|illicit]] [[Wildlife trade|owl trade]] of snowy owls. However, there was no strong evidence of an increase in snowy owls confiscated from the black market, despite a larger than typical number of snowy owls being reported at [[Wildlife rehabilitation|wildlife centres]].<ref>{{cite journal|doi=10.1371/journal.pone.0182368}}</ref> * The [[EADS Harfang]], [[drone aircraft]] developed by the [[French Air Force]], is named in French for the snowy owl (''Harfang des neiges''). * The snowy owl ({{lang|fr|[[wikt:harfang des neiges|harfang des neiges]]}} in French) is the avian symbol of [[Quebec]].<ref>{{cite web|url=https://en.refugepageau.ca/snowy-owl|title=The avian emblem of Quebec|work=Refuge Pageau}}</ref> == References == {{Reflist|30em}} == External links == {{Commons|Bubo scandiacus}} {{Wikispecies|Bubo scandiacus}} * [https://web.archive.org/web/20080724094156/http://www.explorebiodiversity.com/BIRDS/BirdsofWorld/video/SnowyOwl/video.html Free Video About Snowy Owls] * [https://www.theguardian.com/environment/2015/jan/08/snowy-owl-increasingly-casting-spell-north-american-skies Snowy owl increasingly casting its spell over North American skies] (Jan. 2015), ''[[The Guardian (UK)|The Guardian]]'' * [http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/Snowy_Owl.html Snowy Owl Species Account]—Cornell Lab of Ornithology * [https://web.archive.org/web/20150225091841/http://www.mbr-pwrc.usgs.gov/id/framlst/i3760id.html Snowy Owl – ''Nyctea scandiaca'']—USGS Patuxent Bird Identification InfoCenter * {{Avibase|name=Bubo scandiacus}} * {{InternetBirdCollection|snowy-owl-nyctea-scandiaca|Snowy Owl}} * {{VIREO|Snowy+Owl|Snowy Owl}} {{Taxonbar |from=Q170177}} {{DEFAULTSORT:owl, snowy}} [[Category:Bubo (genus)|snowy owl]] [[Category:Birds of the Arctic]] [[Category:Birds of Scandinavia]] [[Category:Holarctic birds]] [[Category:Birds of Manchuria]] [[Category:Birds described in 1758|snowy owl]] [[Category:Provincial symbols of Quebec]] [[Category:Taxa named by Carl Linnaeus|snowy owl]]'
New page wikitext, after the edit (new_wikitext)
'{{Short description|Species of owl}} {{Redirect|Arctic owl|the racehorse|Arctic Owl (horse)}} {{pp-protected|small=yes}} {{Speciesbox | name = Snowy owl | fossil_range= {{Fossil range|Pleistocene|Present}}<ref>{{cite web |title=Bubo scandiacus Linnaeus 1758 (snowy owl) |url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=368622&is_real_user=1 |website=PBDB}}</ref> | status = VU | status_system = IUCN3.1 | status_ref =<ref name="iucn status 19 November 2021">{{cite iucn |author=BirdLife International |date=2020 |title=''Bubo scandiacus'' |volume=2020 |page=e.T22689055A181375387 |doi=10.2305/IUCN.UK.2020-3.RLTS.T22689055A181375387.en |access-date=19 November 2021}}</ref> | image = Snowy Owl (240866707).jpeg | range_map = Cypron-Range Bubo scandiacus.svg | range_map_caption = <br />{{legend0|#0C5F8E|Breeding|border=solid 1px cecece}} {{legend0|#59B1D8|Non Breeding|border=solid 1px cecece}} | genus = Bubo | species = scandiacus | authority = ([[Carl Linnaeus|Linnaeus]], [[10th edition of Systema Naturae|1758]]) | synonyms = *''Strix scandiaca'' {{small|Linnaeus,&nbsp;1758}} *''Strix nyctea'' {{small|Linnaeus,&nbsp;1758}} *''Nyctea scandiaca'' <small>(Linnaeus,&nbsp;1758)</small> }} {{Use dmy dates|date=June 2020}} The '''snowy owl''' (''Bubo scandiacus''), also known as the '''polar owl''', the '''white owl''' and the '''Arctic owl''',<ref name= Potapov>{{cite book|title=The Snowy Owl|author1=Potapov, Eugene |author2=Sale, Richard |name-list-style=amp |publisher = T&APoyser|year = 2013| isbn = 978-0713688177}}</ref> is a large, white [[owl]] of the [[true owl]] family.<ref name= Konig>{{cite book |last=König |first=Claus |title=Owls of the World |year=2008 |publisher=Christopher Helm |location=London |isbn=9781408108840 |edition=2nd |author2=Weick, Friedhelm }}</ref> Snowy owls are native to the [[Arctic]] regions of both North America and the [[Palearctic]], breeding mostly on the [[tundra]].<ref name="iucn status 19 November 2021" /> It has a number of unique adaptations to its habitat and lifestyle, which are quite distinct from other extant owls.<ref name= Voous>{{cite book | last =Voous | first = Karel H. | author-link = Karel H. Voous |author2 = Cameron, Ad (illustrator) |title = Owls of the Northern Hemisphere| year = 1988 | publisher = London, Collins | isbn =978-0-00-219493-8|pages =209–219}}</ref> One of the largest species of owl, it is the only owl with largely white plumage.<ref name= Konig/> Males tend to be a purer white overall while females tend to more have more extensive flecks of dark brown.<ref name= Holt>Holt, D. W., M. D. Larson, N. Smith, D. L. Evans, and D. F. Parmelee (2020). [https://birdsoftheworld.org/bow/species/snoowl1/cur/introduction Snowy Owl (''Bubo scandiacus'')], version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.</ref> Juvenile male snowy owls have dark markings that may appear similar to females until maturity, at which point they typically turn whiter. The composition of brown markings about the wing, although not foolproof, is the most reliable technique to age and sex individual snowy owls.<ref name= Solheim>{{cite journal|author=Solheim, R.|title=Wing feather moult and age determination of Snowy Owls ''Bubo scandiacus''|doi=10.15845/on.v35i0.289|url=https://boap.uib.no/index.php/ornis/article/view/289}}</ref> Most owls sleep during the day and [[Nocturnality|hunt at night]], but the snowy owl is often active during the day, especially in the summertime.<ref name= Voous/> The snowy owl is both a specialized and generalist hunter. Its breeding efforts and entirely global population are closely tied to the availability of tundra-dwelling [[lemming]]s but in the non-breeding season and occasionally during breeding the snowy owl can adapt to almost any available prey, most often other small [[mammal]]s and northerly [[water bird]]s (as well as, opportunistically, [[carrion]]).<ref name= Potapov/><ref name= Holt/> Snowy owls typically nest on a small rise on the ground of the tundra.<ref name= Hume>Hume, R. (1991). ''Owls of the world''. Running Press, Philadelphia.</ref> The snowy owl lays a very large clutch of [[egg]]s, often from about 5 to 11, with the laying and hatching of eggs considerably staggered.<ref name= Holt/> Despite the short [[Climate of the Arctic|Arctic summer]], the development of the young takes a relatively long time and independence is sought in autumn.<ref name= Voous/> The snowy owl is a nomadic bird, rarely breeding at the same locations or with the same mates on an annual basis and often not breeding at all if prey is unavailable.<ref name= Holt/> A largely [[Bird migration|migratory bird]], snowy owls can wander almost anywhere close to the Arctic, sometimes unpredictably [[Animal migration|irrupting]] to the south in large numbers.<ref name= Holt/><ref name= Sindelar>{{cite journal|author=Sindelar Jr., C. |url=https://search.library.wisc.edu/digital/AXWMS2WTWUPCLO8G/pages/AX2FPHBQQK72DD8I|year=1966|title=A comparison of five consecutive Snowy Owl invasions in Wisconsin|journal= Passenger Pigeon|volume= 28|issue=10|pages= 108}}</ref> Given the difficulty of surveying such an unpredictable bird, there was little in depth knowledge historically about the snowy owl's status. However, recent data suggests the species is declining precipitously.<ref name="iucn status 19 November 2021" /><ref name= Bent>Bent, A. C. (1938). ''Life Histories of North American Birds of Prey (part 2), Orders Falconiformes and Stringiformes (Vol. 170)''. US Government Printing Office.</ref> Whereas the global population was once estimated at over 200,000 individuals, recent data suggests that there are probably fewer than 100,000 individuals globally and that the number of successful breeding pairs is 28,000 or even considerably less.<ref name="iucn status 19 November 2021" /><ref name= Marthinsen>{{cite journal|doi=10.1007/s10592-008-9581-6|title=No phylogeographic structure in the circumpolar snowy owl (''Bubo scandiacus'')|url=https://www.researchgate.net/publication/226518592_No_phylogeographic_structure_in_the_circumpolar_Snowy_Owl_Bubo_scandiacus}}</ref> While the causes are not well-understood, numerous, complex environment factors often correlated with [[global warming]] are probably at the forefront of the fragility of the snowy owl's existence.<ref name="iucn status 19 November 2021" /><ref name= Holt/> == Taxonomy == The snowy owl was one of the many [[Aves in the 10th edition of Systema Naturae|bird species originally described]] by [[Carl Linnaeus]] in his landmark 1758 [[10th edition of Systema Naturae|10th edition of ''Systema Naturae'']], where it was given the binomial name ''Strix scandiaca''.<ref>{{cite book | last= Linnaeus | first =Carl | author-link=Carl Linnaeus | title=Systema Naturae per Regna Tria Naturae, Secundum Classes, Ordines, Genera, Species, cum Characteribus, Differentiis, Synonymis, Locis. Tomus I. Editio decima, reformata | publisher= (Laurentii Salvii)|location=[[Stockholm|Holmiae]] | language = la | year=1758| page= 92 | url=https://archive.org/stream/carolilinnaeisy00gesegoog#page/n102/mode/1up}}</ref> The genus name ''Bubo'' is [[Latin]] for an [[horned owl]] and ''scandiacus'' is [[New Latin]] for of [[Scandinavia]].<ref name=job>{{cite book | last= Jobling | first= James A | year= 2010| title= The Helm Dictionary of Scientific Bird Names| url= https://archive.org/details/Helm_Dictionary_of_Scientific_Bird_Names_by_James_A._Jobling/page/n179 | publisher= Christopher Helm | location = London | isbn = 978-1-4081-2501-4 | pages = 179, 349}}</ref> The former genera name ''Nyctea'' is derivation of Greek meaning "night".<ref name= Potapov/> Linnaeus originally described the different plumages of this owl as separate species, with the male specimens of snowy owls being considered ''Strix scandiaca'' and the likely females considered as ''Strix nyctea''.<ref name= Potapov/><ref>{{cite journal|author=Lönnberg, E. |title=Olof Rudbeck, Jr., the first Swedish Ornithologist|journal=Ibis|year=2008|volume=73|issue=2|pages=302–307|doi=10.1111/j.1474-919X.1931.tb01519.x}}</ref> Until recently, the snowy owl was regarded as the sole member of a distinct [[genus]], as ''Nyctea scandiaca'', but [[Mitochondrial DNA|mtDNA]] [[cytochrome b|cytochrome ''b'']] [[Nucleic acid sequence|sequence]] data shows that it is very closely related to the [[horned owl]]s in the genus ''Bubo'' and the species is now thusly often considered inclusive with that genus.<ref name= Wink>Wink, M. & Heidrich, P. (2000). "Molecular systematics of owls (Strigiformes) based on DNA-sequences of the mitochondrial cytochrome b gene", pp. 819–828 in: Chancellor, R.D. & Meyburg, B.U. eds. (2000). ''Raptors at Risk. Proceedings of the V World Conference on Birds of Prey and Owls''. Midrand, Johannesburg, 4–11 August 1998. WWGBP & Hancock House, Berlin & Blaine, Washington.</ref><ref>Penhallurick, J. M. (2002). "The taxonomy and conservation status of the owls of the world: a review". ''Ecology and conservation of owls''. CSIRO, Collingwood, pp. 343–354.</ref> However, some authorities debate this classification, still preferring ''Nyctea''. Often authorities are motivated to retain the separate genus on the grounds of [[Osteology|osteological distinctions]].<ref name= Potapov/><ref name= Ford>Ford, N. L. (1967). ''A systematic study of the owls based on comparative osteology''. PhD diss, Univ. of Michigan, Ann Arbor.</ref> [[File:121 Snowy Owl.jpg|thumb|left|The engraving ''[[Snowy Owl (Audubon)|Snowy Owl]]'', Plate 121 of ''[[The Birds of America]]'' by [[John James Audubon]]. Male (top) and female (bottom).]] Genetic testing revealed a reasonably distinct genetic makeup for snowy owls, being about 8% genetically distinct from other ''Bubo'' owls, perhaps giving credence to those who count the species as separate under ''Nyctea''.<ref name= Potapov/><ref>{{cite journal|pmid=14997323|year=2004|last1=Yamada|first1=K.|last2=Nishida-Umehara|first2=C.|last3=Matsuda|first3=Y.|title=A new family of satellite DNA sequences as a major component of centromeric heterochromatin in owls (Strigiformes)|journal=Chromosoma|volume=112|issue=6|pages=277–287|doi=10.1007/s00412-003-0267-z|s2cid=7848355}}</ref> However, a fairly recent shared origin in evolutionary history has been illustrated through a combination of genetic study and fossil review and there is little, other than osteology of the [[tarsometatarsus]], to outright distinguish the snowy owl from other modern species like the [[Eurasian eagle-owl]] (''Bubo bubo'').<ref name= Potapov/><ref name= Voous/> Genetic testing has indicated that the snowy owl may have diverged from related species at around 4 million years ago.<ref name= Potapov/> Furthermore, it has determined that the living species genetically most closely related to the snowy owl is the [[great horned owl]] (''Bubo virginianus'').<ref name= Potapov/><ref name= Wink2>{{cite journal|doi=10.5253/078.097.0425|title=Molecular Phylogeny of Owls (Strigiformes) Inferred from DNA Sequences of the Mitochondrial Cytochromeband the Nuclear ''RAG-1'' gene|year=2009|last1=Wink|first1=Michael|last2=El-Sayed|first2=Abdel-Aziz|last3=Sauer-Gürth|first3=Hedi|last4=Gonzalez|first4=Javier|journal=Ardea|volume=97|issue=4|pages=581–591|s2cid=55406064}}</ref> On a broader scale, owls in general have, through genetic materials, been determined to be a highly distinct group, with outwardly similar groups such as [[Caprimulgiformes]] revealed to not be at all closely related.<ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/auk/v098n04/p0681-p0714.pdf|author=Cracraft, J.|title=Toward a Phylogenetic Classification of the Recent Birds of the World (Class Aves) |doi=10.1093/auk/98.4.681|doi-broken-date=2021-11-30|journal=The Auk|volume= 98|issue= 4|year= 1981|pages =681–714 }}</ref><ref>{{cite book|doi=10.1016/B978-012498315-1/50014-5|author=Mindell, D. P. |year=1997|chapter=Phylogentic relationships among and within select avian orders based on mitochondrial DNA|title=Avian molecular evolution and systematics|pages= 211–247|publisher= Academic Press|isbn=9780124983151 }}</ref> Within the owl order, [[True owl|typical owls]] are highly divergent from [[barn-owl]]s.<ref name= Konig/><ref name= Wink2/> Furthermore, the ''Bubo'' genus likely clustered at some point during the evolutionary process with other largish owls, such as ''[[Strix (genus)|Strix]]'', ''[[Pulsatrix]]'' and ''[[Ciccaba]]'', based on broad similarities in their voice, reproductive behaviors (i.e. hooting postures) and a similar number and structure of [[chromosome]]s and [[autosome]]s.<ref name= Konig/><ref>{{cite journal|doi=10.1007/BF00056765|title=A karyological study of 55 species of birds, including karyotypes of 39 species new to cytology|year=1984|last1=Belterman|first1=R. H. R.|last2=De Boer|first2=L. E. M.|journal=Genetica|volume=65|pages=39–82|s2cid=37933718}}</ref> A number, but not all, of extant typical owls seem to have evolved from an ancient shared [[common ancestor]] with the ''Bubo'' owls.<ref name= Schmutz>{{cite journal|doi=10.1139/g91-110|title=A cytogenetic comparison of some North American owl species|year=1991|last1=Schmutz|first1=Sheila M.|last2=Moker|first2=Jane S.|journal=Genome|volume=34|issue=5|pages=714–717}}</ref> In addition to the question of relationship of the traditional ''Bubo'' owls to the snowy owls, ongoing ambiguity of the relationship of other similarly large-sized owls has been persistent. These have sometimes either been included in the genus or within separate genera, i.e. the ''[[Fish owl|Ketupu]]'' or fish owls and the ''[[Fishing owl|Scotopelia]]'' or fishing owls. Despite the adaptive distinctions, the grouping of these large owls (i.e. ''Bubo'', snowy, fish and perhaps fishing owls) appears to be borne out via research of [[karyotype]]s.<ref name= Konig/><ref name= Schmutz/><ref name= Wink2/><ref name= Mikkola>''Owls of the World: A Photographic Guide'' by Mikkola, H. Firefly Books (2012), {{ISBN|9781770851368}}</ref><ref>{{cite journal|doi=10.1071/MU02006|url=https://www.researchgate.net/publication/248900150|title=A new Ninox owl from Sumba, Indonesia|year=2002|last1=Olsen|first1=Jerry|last2=Wink|first2=Michael|last3=Sauer-Gürth|first3=Hedi|last4=Trost|first4=Susan|journal=Emu - Austral Ornithology|volume=102|issue=3|pages=223–231|s2cid=86526031}}</ref> The [[fossil]] history of snowy owls is fairly well documented despite some early confusion on how to distinguish the skeletal structure of the snowy owls from eagle-owls.<ref name= Brodkorb>{{cite journal|url=https://ufdc.ufl.edu/UF00001516/00001|author=Brodkorb, P. |year=1971|title=Catalogue of fossil birds, Part 4 (Columbiformes through Piciformes)|journal= Bulletin of the Florida State Museum, Biological Sciences |volume=15|issue=4|page=163}}</ref><ref>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V100/V100_N08/V100_N8_28_33.pdf|author=Stewart, J. R. |year=2007|title=The fossil and archaeological record of the Eagle Owl in Britain|journal= British Birds|volume= 100|issue=8|pages= 481}}</ref> It was determined that the snowy owl once was distributed much more widely and far farther to the south during the [[Quaternary glaciation]] when much of the [[Northern Hemisphere]] was in the midst of an [[ice age]].<ref name= Potapov/> Fossil records shows that snowy owls once could be found in Austria, Azerbaijan, [[Czechoslovakia]], England, France, Germany, Hungary, Italy, Poland, Sardinia and Spain as well as in the Americas in [[Cape Prince of Wales]], [[Little Kiska Island]], [[St. Lawrence Island]], and in [[Illinois]].<ref name= Holt/><ref name= Brodkorb/> In the [[Late Pleistocene]] the range expanded southward even more so to Bulgaria (80,000–16,000 years, [[Kozarnika]] Cave, W Bulgaria).<ref>{{cite journal|author=Boev, Z.|year= 1998|title= First fossil record of the Snowy Owl ''Nyctea scandiaca'' (Linnaeus, 1758) (Aves: Strigidae) from Bulgaria|url=https://www.researchgate.net/publication/301215428|journal=Historia Naturalis Bulgarica|volume= 9|pages= 79–86}}</ref> and much of the Italian Peninsula.<ref>{{Cite book|author1=Bedetti, C. |author2=Palombo, M.R. |author3=Sardella, R. |date= October 2001|title=1st International Congress "The World of Elephants"|chapter=Last occurrences of large mammals and birds in the Late Quaternary of the Italian peninsula|chapter-url=https://iris.uniroma1.it/handle/11573/253607|pages=701–703|isbn=978-88-8080-025-5}}</ref> [[Pleistocene]] era fossil from France, i.e. ''B. s. gallica'', showed that the snowy owls of the time were somewhat bulkier (though still notably smaller than [[Eurasian eagle-owl|contemporary eagle-owls]] of the times, which were larger than the eagle-owls of today) and ostelogically more sexually dimorphic in size than the modern form (9.9% dimorphism in favor of females in the fossils against 4.8% in the same features today).<ref>Andrews, P. (1990). ''Owls, caves and fossils''. Chicago: University of Chicago Press.</ref> There are no subspecific or other geographical variations reported in the modern snowy owls, with individuals of vastly different origins breeding together readily due to their nomadic habits.<ref name= Holt/> Despite apparent variations in body size, environment conditions are the likely variant rather than genetics.<ref name= Potapov/> No evidence could be found of [[Phylogeography|phylogeographic variation]] could be found in snowy owls upon testing. Furthermore, the snowy owl appears to have a similar level of [[genetic diversity]] as other European owls.<ref name= Marthinsen/><ref>Marthinsen, G., Wennerberg, L., Solheim, R., & Lifjeld, J. T. (2009). Snowy owls (''Bubo scandiacus'') constitute one panmictic population. University of Oslo.</ref> ===Hybrids=== Snowy owls are not known to interbreed with other owl species in the wild, and accordingly, no hybrids of snowy owls and other owl species have yet been sighted in the wild. However, a hobby falconer in [[Kollnburg]], Germany, bred [[Hybrid (biology)|hybrids]] from a male snowy owl and a female Eurasian eagle-owl (''Bubo bubo'') in 2013.<ref>[http://www.tz.de/bayern/ueberraschende-kreuzung-tierreich-schnuhu-mischung-schneeeule-eule-3069906.html "Schnuhu": Überraschende Kreuzung – Ich bin Bayerns süßester Fratz!]. tz.de Retrieved on 7 October 2016</ref> The two resulting male hybrid owls possessed the prominent ear tufts (generally absent in snowy owls), general size, orange eyes, and the same pattern of black markings on their plumage from their Eurasian eagle-owl mother, while retaining the generally black-and-white plumage colours from their snowy owl father. The hybrids were dubbed "''Schnuhus''" from the German words for snowy owl and Eurasian eagle-owl (''Schnee-Eule'' and ''Uhu'', respectively). As of 2014, the hybrids had grown to maturity and were healthy.{{cn|date=March 2021}} == Description == [[File:Bubo scandiacus (Linnaeus, 1758) Male.jpg|thumb|left|A captive adult male.]] The snowy owl is mostly white. They are purer white than predatory mammals like [[polar bear]]s (''Ursus maritimus'') and [[Arctic fox]] (''Vulpes lagopus'').<ref name= Hume/> Often when seen in the field, these owls can resemble a pale rock or a lump of snow on the ground.<ref name= Hume/> It usually appears to lack ear tufts but very short (and probably vestigial) [[Ear tuft|tufts]] can be erected in some situations, perhaps most frequently by the female when she is sitting on the nest.<ref name= Konig/> The ear tufts measure about {{convert|20|to|25|mm|in|abbr=on}} and consist of about 10 small feathers.<ref name= Voous/> The snowy owl has bright yellow eyes.<ref name= Holt/> The head is relatively small and, even for the relatively simply adapted hearing mechanism of a ''Bubo'' owl, the [[facial disc]] is shallow and the ear is uncomplicated.<ref name= Konig/><ref name= Voous/> 1 male had ear slits of merely {{convert|21|x|14|mm|in|abbr=on}} on left and {{convert|21|x|14.5|mm|in|abbr=on}} on the right.<ref name= Voous/> Females are almost invariably more duskily patterned than like-age males.<ref name= Konig/><ref name= Holt/> In mature males, the upper parts are plain white with usually a few dark spots on the miniature ear-tufts, about the head and the tips of some [[Flight feather|primaries and secondaries]] whilst the underside is often pure white.<ref name= Konig/> Despite their reputation for being purely white, only 3 out of 129 Russian museum specimens of adult males showed an almost complete absence of darker spots. The adult female is usually considerably more spotted and often slightly barred with dark brown on the crown and the underparts. Her flight and tail feathers are faintly barred brown while the underparts are white in base color with brown spotting and barring on the flanks and upper breast.<ref name= Konig/> In confusingly plumaged snowy owls, the sex can be determined by the shape of wing markings, which manifest as bars more so in females and spots in males.<ref name= Potapov/><ref name= Lind>{{cite journal|url=https://journals.lub.lu.se/os/article/view/23039|volume=3|year=1993|author=Lind, H. |title=Different ecology in male and female wintering Snowy Owls ''Nyctea scandiaca'' L. in Sweden due to colour and size dimorphism}}</ref> However, the very darkest males and the lightest females are nearly indistinguishable by plumage.<ref name= Potapov/> On rare occasion, a female can appear almost pure white, as has been recorded in both the field and in captivity.<ref name= McMorris>McMorris, A. (2011). ''Snowy Owls: Age, Sex and Plumage''. Presentation Delaware Valley Ornithological Club.</ref> There is some evidence that some of the species grow paler with age after maturity.<ref name= Holt/><ref name= Dementiev>Dementiev, G. P., Gladkov, N. A., Ptushenko, E. S., Spangenberg, E. P., & Sudilovskaya, A. M. (1966). ''Birds of the Soviet Union, vol. 1''. Israel Program for Scientific Translations, Jerusalem.</ref> One study's conclusions were that males were usually but not always lighter and that correctly aging is extremely difficult, sometimes individuals either get lighter, darker or do not change their appearance with age.<ref name= McMorris/> On the other hand, with close study, it is possible to visually identify even individual snowy owls using the pattern of markings on the wing, which can be somewhat unique in each individual.<ref>{{cite journal|title=Identifying Individual Great Gray Owls (''Strix nebulosa'') and Snowy Owls (''Bubo scandiacus'') Using Wing Feather Bar Patterns|url=https://www.researchgate.net/publication/311484678_Identifying_Individual_Great_Gray_Owls_Strix_nebulosa_and_Snowy_Owls_Bubo_scandiacus_Using_Wing_Feather_Bar_Patterns|doi=10.3356/JRR-15-64.1| last=Solheim | first=Roar| volume=50 | issue=4 | year=2016| pages=370–378}}</ref> After a [[Moulting|fresh moult]], some adult females that previously appeared relatively pale newly evidenced dark, heavy markings. On the contrary, some banded individuals over at least four years were observed to have been almost entirely unchanged in the extent of their markings.<ref name= Potapov/><ref name= Holt/> In another very pale owl, the [[barn owl]] (''Tyto alba''), the sexual dimorphism of spotting appears to be driven by genetics while, in snowy owls, environment may be the dictating factor instead.<ref name= Potapov/><ref>{{cite journal|title=Genetic, environmental, and condition‐dependent effects on female and male ornamentation in the barn owl ''Tyto alba''|pmid=28565392| last=Roulin | first=Alexandre | last2=Richner | first2=Heinz | last3=Ducrest | first3=Anne-Lyse| journal=Evolution| volume=52 | issue=5 | year=1998| pages=1451–1460}}</ref> [[File:Snowy Owl - Schnee-Eule.jpg|thumb|right|A captive adult female.]] The chicks are initially grayish white but quickly transition to dark gray-brown in the mesoptile plumage. This type of plumage [[camouflage]]s effectively against the variously colored [[lichen]]s that dot the tundra ground.<ref name= Konig/><ref name= Holt/> This is gradually replaced by plumage showing dark barring on white. At the point of fledging, the plumage often becomes irregularly mottled or blotched with dark and is mostly solidly dark gray-brown above with white eyebrows and other areas of the face white.<ref name= Konig/> Recently fledged young can already be sexed to a semi-reliable degree by the dark marking patterns about their wings.<ref name= Seidensticker>{{cite journal|doi=10.3356/JRR-11-02.1| last=Seidensticker | first=Mathew T. | last2=Holt | first2=Denver W. | last3=Detienne | first3=Jennifer | last4=Talbot | first4=Sandra | last5=Gray | first5=Kathy | title=Sexing Young Snowy Owls | journal=Journal of Raptor Research| volume=45 | issue=4 | year=2011| pages=281–289}}</ref> The juvenile plumage resembles that of adult females but averages slightly darker on average.<ref name= Holt/> By their second [[Moulting|moult]] fewer or more broken bars are usually evidenced on the wing. The extent of white and composition of wing patterns become more dimorphic by sex with each juvenile moult, culminating in the 4th or 5th pre-basic moult, wherein the owls are hard to distinguish from mature adults.<ref name= Potapov/><ref name= Holt/><ref name= Solheim/><ref name= Seidensticker/><ref>{{cite journal|author=Pyle, P.|title=Flight-feather molt patterns and age in North American owls|doi=10.2307/4089230|url=https://www.birdpop.org/docs/pubs/Pyle_1997_Flight_Feather_Molt_Patterns_and_Age_in_NA_Owls.pdf| pages=553| volume=115 | issue=2 | year=1998}}</ref> Moults usually occur from July and September, non-breeding birds moulting later and more extensively, and are never extensive enough to render the owls flightless.<ref name= Potapov/> Evidence indicates that snowy owls may attain adult plumage at 3 to 4 years of age, but fragmentary information suggests that some males are not fully mature and/or as fully white in plumage that they can attain until the 9th or 10th year.<ref name= Holt/><ref name= Seidensticker/><ref name= Cramp>{{cite book |last1=Cramp |first1=S. |last2=Simmons |first2=K.E.L. |year=1985 |title=Birds of the Western Palearctic |volume=Vol. 2 |publisher=Oxford University Press |location=Oxford}}</ref> Generally speaking, moults of snowy owls occur more quickly than do those of Eurasian eagle-owls.<ref name= Solheim/> The toes of the snowy owl are extremely thickly feathered white, while the claws are black.<ref name= Konig/> The toe feathers are the longest known of any owl, averaging at {{convert|33.3|mm|in|abbr=on}}, against the great horned owl which has the 2nd longest toe feathers at a mean of {{convert|13|mm|in|abbr=on}}<ref name= Voous/><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/condor/v083n04/p0302-p0309.pdf|author=Barrows, C. W. |year=1981|title=Roost selection by spotted owls: an adaptation to heat stress|journal= Condor|volume= 83|issue=4|pages= 302–309}}</ref> Occasionally, snowy owls may show a faint blackish edge to the eyes and have a dark gray cere, though this is often not visible from the feather coverage, and a black bill.<ref name= Konig/> Unlike many other whitish birds, the snowy owl does not possess black wingtips, which is theorized to minimize wear-and-tear on the wing feathers in the other whitish bird types.<ref>{{cite journal|doi=10.2307/1362901| last=Averill | first=Charles K. | title=Black Wing Tips | journal=The Condor| volume=25 | issue=2 | year=1923| pages=57–59|jstor=1362901|url=https://sora.unm.edu/sites/default/files/journals/condor/v025n02/p0057-p0059.pdf}}</ref> The conspicuously notched primaries of the snowy owl appear to give an advantage over similar owls in long-distance flight and more extensive flapping flight.<ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/condor/v029n01/p0017-p0018.pdf|title=Emargination of the Long Primaries in Relation to Power of Flight and Migration with One Illustration| volume=29 | issue=1 | year=1927| pages=17–18| last=Averill | first=C. K.| journal=The Condor|doi=10.2307/1363004}}</ref> The snowy owl does have some of the noise-canceling serrations and comb-like wing feathers that render the flight of most owls functionally silent, but they have fewer than most related ''Bubo'' owls. Therefore, in combination with its less soft feathers, the flight of a snowy owl can be somewhat audible at close range.<ref name= Potapov/><ref>{{cite journal|pmid=28163870| last=Wagner | first=Hermann | last2=Weger | first2=Matthias | last3=Klaas | first3=Michael | last4=Schröder | first4=Wolfgang | title=Features of owl wings that promote silent flight | journal=Interface Focus | volume=7 | issue=1 | date=2017| doi=10.1098/rsfs.2016.0078 | page=20160078}}</ref> The flight of snowy owls tends to be steady and direct and is reminiscent to some of the flight of a large, slow-flying falcon.<ref name= Potapov/> Though capable of occasional [[Flying and gliding animals|gliding flight]], there is no evidence that snowy owls will [[Bird flight|soar]]. It is said that the species seldom exceeds a flying height of around {{convert|150|m|ft|abbr=on}} even during passage.<ref name= Potapov/> While the feet are sometimes described as "enormous", the [[Tibiotarsus|tarsus]] is in osteological terms relatively short at 68% the length of those of a Eurasian eagle-owl but the claws are nearly as large, at 89% of the size of those of the eagle-owl.<ref name= Voous/><ref name= Hume/><ref name= Ford/> Despite its relatively short length, the tarsus is of similar circumference as in other ''Bubo'' owls.<ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/jfo/v013n01/p0009-p0012.pdf|author1=Stabler, R. M.|author2 =Hoy, N. D. |year=1942|title=Measurements of Tarsal Circumferences from Living Raptorial Birds|journal= Bird-Banding|pages= 9–12|volume=13|issue=1}}</ref> Also compared to an eagle-owl, the snowy owl has a relatively short decurved [[Rostrum (anatomy)|rostrum]], a proportionately greater length to the [[Interorbital region|interorbital roof]] and a much longer [[sclerotic ring]] surrounding the eyes while the anterior opening are the greatest known in any owl.<ref name= Voous/><ref name= Ford/><ref>{{cite journal|pmid=16717442| last=Iwaniuk | first=Andrew N. | last2=Hurd | first2=Peter L. | last3=Wylie | first3=Douglas R.W. | title=Comparative Morphology of the Avian Cerebellum: I. Degree of Foliation | journal=Brain, Behavior and Evolution| volume=68 | issue=1 | year=2006 | doi=10.1159/000093530 | pages=45–62}}</ref> Owls have extremely large eyes which are nearly the same size in large species such as the snowy owl as those of humans.<ref>Gill, F. (2007). ''Ornithology''. 3rd Edn. (W. H. Freeman Co: New York.</ref> The snowy owl's eye, at about {{convert|23.4|mm|in|abbr=on}} in diameter, is slightly smaller than those of great horned and Eurasian eagle-owls but is slightly larger than those of some other [[Great grey owl|large owls]].<ref name= Voous/><ref>{{cite journal| last=Wills | first=Sarah | last2=Pinard | first2=Chantale | last3=Nykamp | first3=Stephanie | last4=Beaufrère | first4=Hugues| journal=Journal of Zoo and Wildlife Medicine | volume=47 | issue=1 | year=2016 | doi=10.1638/2015-0009.1 | pages=244–255|title=Ophthalmic reference values and lesions in two captive populations of northern owls: great grey owls (''Strix nebulosa'') and snowy owls (''Bubo scandiacus'')}}</ref> Snowy owls must be able to see from great distances and in highly variable conditions but probably possess less acute night vision than many other owls.<ref name= Potapov/> Based on the study of [[dioptre]]s in different owl species, the snowy owl was determined to have eyesight better suited to long-range perception than to close discrimination, while some related species such as great horned owls could probably more successful perceive closer objects.<ref>{{cite journal|doi=10.1007/BF00623904| last=Murphy | first=C. J. | last2=Howland | first2=H. C. | title=Owl eyes: Accommodation, corneal curvature and refractive state | journal=Journal of Comparative Physiology A| volume=151 | issue=3 | year=1983| pages=277–284 }}</ref> Despite their visual limits, snowy owls may have up to 1.5 times more visual acuity than humans.<ref name= Potapov/> Like other owls, snowy owls can probably perceive all colors but cannot perceive [[ultraviolet]] visual pigments.<ref>{{cite journal|pmid=716232| last=Bowmaker | first=J.K. | last2=Martin | first2=G.R. | journal=Vision Research| volume=18 | issue=9 | year=1978 | doi=10.1016/0042-6989(78)90095-0 | pages=1125–1130|title=Visual pigments and colour vision in a nocturnal bird, ''Strix aluco'' (tawny owl)}}</ref><ref>{{cite journal|pmid=4446369|title=Visual acuity in the tawny owl (''Strix aluco'')| doi=10.1016/0042-6989(74)90014-5 | pages=1393–1397| last=Martin | first=Graham R. | last2=Gordon | first2=Ian E. | journal=Vision Research}}</ref><ref>{{cite journal|pmid=24258716| last=Lind | first=Olle | last2=Mitkus | first2=Mindaugas | last3=Olsson | first3=Peter | last4=Kelber | first4=Almut | title=Ultraviolet vision in birds: the importance of transparent eye media | journal=Proceedings of the Royal Society B: Biological Sciences | volume=281 | issue=1774 | date=2014| doi=10.1098/rspb.2013.2209 | page=20132209}}</ref><ref>{{cite journal|doi=10.1007/BF00616750| last=Burkhardt | first=Dietrich | title=UV vision: a bird's eye view of feathers | journal=Journal of Comparative Physiology A| volume=164 | issue=6 | year=1989| pages=787–796}}</ref> Owls have the largest brains of any bird (increasing in sync with the size of the owl species), with the size of the brain and eye related less to [[intelligence]] than perhaps to increased nocturnality and predatory behavior.<ref>{{cite journal|pmid=12028780| last=Garamszegi | first=L. Z. | last2=Møller | first2=A. P. | last3=Erritzøe | first3=J. | title=Coevolving avian eye size and brain size in relation to prey capture and nocturnality | journal=Proceedings of the Royal Society of London. Series B: Biological Sciences | volume=269 | issue=1494 | date=2002| doi=10.1098/rspb.2002.1967 | pages=961–967}}</ref> ===Size=== [[File:Snowy Owl Barrow Alaska.jpg|thumb|left|Young owl on the tundra at [[Utqiaġvik]], Alaska. Snowy owls lose their black feathers with age, although individual females may retain some]] The snowy owl is a very large owl.<ref name= Konig/> They are the largest avian predator of the [[Arctic|High Arctic]] and one of the largest owls in the world.<ref name= Voous/> Snowy owls are about the sixth or seventh heaviest living owl on average, around the fifth longest and perhaps the third longest winged.<ref name= Konig/><ref name= Mikkola/><ref name= Weidensaul>Weidensaul, S. (2015). ''Owls of North America and the Caribbean''. Houghton Mifflin Harcourt.</ref><ref name= CRC>{{cite book |title=CRC Handbook of Avian Body Masses |edition=2nd |editor-first=John B. Jr. |editor-last=Dunning |publisher=CRC Press |year=2008 |isbn=978-1-4200-6444-5}}</ref> This species is the heaviest and longest winged owl (as well as the second longest) in North America, the second heaviest and longest winged owl in Europe (and third longest) but is outsized in bulk by about 3 to 4 other species in Asia.<ref name= Potapov/><ref name= Cramp/><ref name= Weidensaul/><ref>{{cite journal|doi=10.2307/4078421| last=Poole | first=Earl L. | title=Weights and Wing Areas in North American Birds | journal=The Auk| volume=55 | issue=3 | year=1938| pages=511–517}}</ref> Despite being sometimes described as of similar size, the snowy owl is somewhat larger in all aspects of average size than the [[great horned owl]] while the similarly specialized [[taiga]]-dwelling [[great grey owl]] (''Strix nebulosa''), is longer in total length and of similar dimensions in standard measurements, but is shorter winged and much less heavy than the snowy owl.<ref name= Potapov/><ref name= Weidensaul/><ref name= CRC/> In Eurasia, the [[Eurasian eagle-owl]] is larger in all standards of measurements than the snowy owl not to mention two additional species each from Africa and Asia that are slightly to considerably heavier on average than the snowy owl.<ref name= CRC/> Like most [[birds of prey]], the snowy owl shows [[Sexual dimorphism|reverse sexual dimorphism]] relative to most non-raptorial birds in that females are larger than males.<ref name= Potapov/> Sexual dimorphism that favors the female may have some correlation with being able to more effectively withstand food shortages such as during brooding as well as the rigors associated with incubating and brooding.<ref>{{cite journal|doi=10.2307/3676862| last=Lundberg | first=Arne | title=Adaptive Advantages of Reversed Sexual Size Dimorphism in European Owls | journal=Ornis Scandinavica| volume=17 | issue=2 | year=1986 | page=133}}</ref> Females are sometimes described as “giant” whereas males appear relatively “neat and compact”.<ref name= Hume/> However, the sexual dimorphism is relatively less pronounced compared to some other ''Bubo'' species.<ref name= Potapov/><ref name= Weick>{{cite book |title=Owls (Strigiformes): Annotated and Illustrated Checklist |last=Weick |first=Friedhelm |year=2007 |publisher=Springer |isbn=978-3-540-39567-6}}</ref><ref>{{cite journal| last=Korpimaki | first=Erkki | title=Reversed Size Dimorphism in Birds of Prey, Especially in Tengmalm's Owl ''Aegolius funereus'': A Test of the "Starvation Hypothesis" | journal=Ornis Scandinavica | volume=17 | issue=4 | year=1986 | doi=10.2307/3676820 | page=326}}</ref> Male snowy owls have been known to measure from {{convert|52.5|to|64|cm|in|abbr=on}} in total length, with an average from four large samples of {{convert|58.7|cm|in|abbr=on}} and a maximum length, perhaps in need of verification, of reportedly {{convert|70.7|cm|in|abbr=on}}.<ref name= Eckert>Eckert, A. W. (1987). ''The Owls of North America, North of Mexico: All the Species and Subspecies Illustrated in Color and Fully Described''. Gramercy.</ref><ref name= Parmelee>Parmelee, D. F. (1972). ''Canada's incredible arctic owls''. Beaver no. summer:30–41.</ref><ref name= Priklonskiy>Priklonskiy, S.G. (1993). ''Snowy Owl — Nyctea scandiaca (Linnaeus, 1758)''. In: ''Birds of Russia and adjoining regions: Pterocliformes, Columbiformes, Cuculiformes, Strigiformes''. Moscow, p. 258–270. (in Russian).</ref><ref name= Keith>{{cite journal|author=Keith, L.B. |year=1960|title=Observations of Snowy Owls at Delta, Manitoba|journal= Canadian Field-Naturalist|volume= 74|pages=106–112}}</ref> In wingspan, males may range from {{convert|116|to|165.6|cm|ftin|0|abbr=on}}, with a mean of {{convert|146.6|cm|ftin|0|abbr=on}}.<ref name= Dementiev/><ref name= Eckert/><ref name= Priklonskiy/><ref name= Keith/> In females, total length has been known to range from {{convert|54|to|71|cm|in|abbr=on}}, with a mean of {{convert|63.7|cm|in|abbr=on}} and an unverified maximum length of perhaps {{convert|76.7|cm|in|abbr=on}} (if so they would have the second longest maximum length of any living owl, after only the great grey owl).<ref name= Eckert/><ref name= Parmelee/><ref name= Priklonskiy/><ref name= Keith/> Female wingspans have reportedly measured from {{convert|146|to|183|cm|ftin|0|abbr=on}}, with a mean of {{convert|159|cm|ftin|0|abbr=on}}.<ref name= Eckert/><ref name= Priklonskiy/><ref name= Keith/> Despite one study claiming that snowy owl had the highest [[wing loading]] (i.e. grams per square cm of wing area) of any of 15 well-known owl species, more extensive sampling demonstratively illustrated that the wing loading of snowy owls is notably lower than Eurasian eagle- and great horned owls.<ref name= Mikkola/> The conspicuously long-winged profile of a flying snowy owl compared to these related species may cause some to compare their flight profile to a bulkier version of an enormous ''[[Buteo]]'' or a large [[falcon]].<ref name= Potapov/> Body mass in males can average from {{convert|1465|to|1808.3|g|lb|abbr=on}}, with a median of {{convert|1658.2|g|lb|abbr=on}} and a full weight range of {{convert|1300|to|2500|g|lb|abbr=on}} from six sources.<ref name= Konig/><ref name= Dementiev/><ref name= Eckert/><ref name= Priklonskiy/><ref name= Keith/><ref name= Earhart>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/condor/v072n03/p0251-p0264.pdf| last=Earhart | first=Caroline M. | last2=Johnson | first2=Ned K. | title=Size Dimorphism and Food Habits of North American Owls | journal=The Condor| volume=72 | issue=3 | year=1970| pages=251–264|doi=10.2307/1366002}}</ref><ref name= Kerlinger>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/jfo/v059n01/p0007-p0012.pdf|author1=Kerlinger, P.|author2=Lein, M. R. |year=1988|title=Causes of Mortality, Fat Condition, and Weights of Wintering Snowy Owls|journal= Journal of Field Ornithology|volume=59|issue=1|pages= 7–12}}</ref> Body mass in females can average from {{convert|1706.7|to|2426|g|lb|abbr=on}}, with a median of {{convert|2101.8|g|lb|abbr=on}} and a full weight range of {{convert|1330|to|2951|g|lb|abbr=on}}.<ref name= Dementiev/><ref name= Eckert/><ref name= Priklonskiy/><ref name= Keith/><ref name= Earhart/><ref name= Kerlinger/><ref>National Geographic Society. [http://animals.nationalgeographic.com/animals/birds/snowy-owl.html "Snowy Owl"].</ref> Larger than the aforementioned body mass studies, a massive pooled dataset at six wintering sites in North America showed that 995 males averaged at {{convert|1636|g|lb|abbr=on}} while 1,189 females were found to average {{convert|2109|g|lb|abbr=on}}.<ref name= Holt/><ref>{{cite journal|title=Mass growth rates, plumage development, and related behaviors of Snowy Owl (''Bubo scandiacus'') nestlings|doi=10.3356/rapt-50-02-131-143.1| last=Holt | first=Denver W. | last2=Gray | first2=Kathy | last3=Maples | first3=Michael T. | last4=Korte | first4=Mark A. | journal=Journal of Raptor Research| volume=50 | issue=2 | year=2016| pages=131–143}}</ref><ref name= Chang>{{cite journal| last=Chang | first=Alexander M. | last2=Wiebe | first2=Karen L. | journal=The Auk| volume=133 | issue=4 | year=2016| pages=738–746|title=Body condition in Snowy Owls wintering on the prairies is greater in females and older individuals and may contribute to sex-biased mortality|doi=10.1642/AUK-16-60.1|url=https://www.researchgate.net/publication/307548228_Body_condition_in_Snowy_Owls_wintering_on_the_prairies_is_greater_in_females_and_older_individuals_and_may_contribute_to_sex-biased_mortality}}</ref> Reported weights of down to {{convert|710|g|lb|abbr=on}} for males and of {{convert|780|to|1185|g|lb|abbr=on}} for females are probably in reference to owls in a state of [[starvation]].<ref name= Konig/><ref name= Potapov/><ref name= Pitelka>{{cite journal|doi=10.2307/1364693| last=Pitelka | first=Frank A. | last2=Tomich | first2=P. Quentin | last3=Treichel | first3=George W. | title=Breeding Behavior of Jaegers and Owls near Barrow, Alaska | journal=The Condor| volume=57 | issue=1 | year=1955| pages=3–18|url=https://sora.unm.edu/sites/default/files/journals/condor/v057n01/p0003-p0018.pdf}}</ref> Such emaciated individuals are known to highly impaired and starvation deaths are probably not infrequent in winters with poor food accesses.<ref name= Potapov/><ref name= Pitelka/> [[File:The bird, its form and function (1906) (14755679525).jpg|thumb|left|Snowy owls have powerful feet that are heavily covered with feathering.]] Standard measurements have been even more widely reported than length and wingspan.<ref name= Potapov/> The [[Wing chord (biology)|wing chord]] of males can vary from {{convert|351|to|439|mm|in|abbr=on}}, averaging from {{convert|380.1|to|412|mm|in|abbr=on}} with a median of {{convert|402.8|mm|in|abbr=on}}.<ref name= Dementiev/><ref name= Eckert/><ref name= Parmelee/><ref name= Priklonskiy/><ref name= Earhart/><ref name= Josephson>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/jfo/v051n02/p0149-p0160.pdf|author=Josephson, B. |year=1980|title=Aging and sexing snowy owls|journal= Journal of Field Ornithology |volume=51|pages= 149–160}}</ref> The wing chord of females can vary from {{convert|380|to|477.3|mm|in|abbr=on}}, averaging from {{convert|416.2|to|445|mm|in|abbr=on}} with a median of {{convert|435.5|mm|in|abbr=on}}.<ref name= Dementiev/><ref name= Eckert/><ref name= Parmelee/><ref name= Priklonskiy/><ref name= Earhart/><ref name= Josephson/> The [[tail]] length of males can vary on average from {{convert|209.6|to|235.4|mm|in|abbr=on}}, with a full range of {{convert|188|to|261|mm|in|abbr=on}} and a median of {{convert|227|mm|in|abbr=on}}.<ref name= Eckert/><ref name= Parmelee/><ref name= Priklonskiy/><ref name= Keith/><ref name= Josephson/> The tail length of females can average from {{convert|228.5|to|254.4|mm|in|abbr=on}}, with a full range of {{convert|205|to|288|mm|in|abbr=on}} and a median of {{convert|244.4|mm|in|abbr=on}}.<ref name= Eckert/><ref name= Parmelee/><ref name= Priklonskiy/><ref name= Keith/><ref name= Josephson/> Data indicates that slightly longer wing chord and tail lengths were reported on average in Russian data than in American research, however the weights were not significantly different in the two regions.<ref name= Kerlinger/> Less widely taken measurements include the [[Culmen (bird)|culmen]], which can measure from {{convert|24.6|to|29|mm|in|abbr=on}} with a median average of {{convert|26.3|mm|in|abbr=on}} in males and {{convert|27.9|mm|in|abbr=on}} in females, and the [[Beak|total bill]] length which is from {{convert|25|to|42|mm|in|abbr=on}}, with an average in both sexes of {{convert|35.6|mm|in|abbr=on}}.<ref name= Eckert/><ref name= Parmelee/><ref name= Priklonskiy/> [[Tibiotarsus|Tarsal length]] in males averages about {{convert|63.6|mm|in|abbr=on}}, with a range of {{convert|53|to|72|mm|in|abbr=on}}, and averages about {{convert|66|mm|in|abbr=on}}, with a range of {{convert|54|to|75|mm|in|abbr=on}}, in females.<ref name= Parmelee/><ref name= Priklonskiy/> ===Identification=== [[File:Bubo scandiacus male Muskegon.jpg|thumb|right|Male snowy owls such as this are particularly distinctive due to the extensive whiteness.]] The snowy owl is certainly one of the most unmistakable owls (or perhaps even animals) in the world.<ref name= Voous/><ref name= Hume/> No other species attains the signature white stippled sparsely with black-brown color of these birds, a coloring which renders their bright yellow eyes all the more detectable, nor possesses their obvious extremely long feathering.<ref name= Konig/> The only other owl to breed in the [[Arctic|High Arctic]] is the [[short-eared owl]] (''Asio flammeus''). Both species inhabit open country, overlap in range and are often seen by day, but the short-eared is much smaller and more tan or straw-colored in coloration, with streaked brown on chest. Even the palest short-eared owls conspicuously differ and are darker than the snowy owl; additionally the short-eared most often hunts in extended flights.<ref name= Holt/><ref name="Pyle">Pyle, P. (1997). ''Identification Guide to North American Birds, Part I: Columbidae to Ploceidae''. Slate Creek Press, Bolinas, CA, USA.</ref> More similar owls such as the [[Eurasian eagle-owl]] and the [[great horned owl]] attain a fairly pale, sometimes white-washed look in their northernmost races. These species do not normally breed nearly as far north as snowy owls but overlaps certainly do occur when snowy owls when the latter owl sometimes comes south in winter. However, even the most pale great horned and Eurasian eagle-owls are still considerably more heavily marked with darker base colors than snowy owls (the whitest eagle-owls are paler than the whitest great horned owls), possess much larger and more conspicuous [[ear tuft]]s and lack the bicolored appearance of the darkest snowy owls. While the great horned owl has yellow eyes like the snowy owl, the Eurasian eagle-owl tends to have bright orange eyes. The [[open terrain]] habitats normally used by wintering snowy owls are also distinct from the typical [[Woodland edge|edge]] and [[Rock (geology)|rock]]y habitats usually favored by the great horned and Eurasian eagle-owls, respectively.<ref name= Konig/><ref>{{cite book|last=Smith|first=Dwight G.|title=Great Horned Owl|year=2002|publisher=Stackpole Books|location=Mechanicsburg, PA |url=https://books.google.com/books?id=f1PVJVWbQKwC |isbn=978-0811726894 |pages=33; 80–81 |edition=1st }}</ref><ref name="Pyle" /> ===Vocalizations=== The snowy owl differ in their calls from other ''Bubo'' owls, with a much more barking quality to their version of a hooting song.<ref name= Hume/> Perhaps as many as 15 different calls by mature snowy owls have been documented.<ref name= Evans>{{cite journal|url=https://sora.unm.edu/node/112819|author=Evans, D. L. |year=1980|title=Vocalizations and territorial behavior of wintering Snowy Owls|journal=Am. Birds|volume= 34|pages= 748–749}}</ref><ref name= Sutton1>Sutton, G. M. (1932). ''The exploration of Southampton Island. Part II, Zoölogy. Section 2.-The birds of Southampton Island''. Memoirs of the Carnegie Museum 12 (2):1–275.</ref> The main vocalization is a monotonous sequence that normally contains 2–6 (but occasionally more), rough notes similar to the rhythm of a barking dog: ''krooh krooh krooh krooh''...<ref name= Konig/> The call may end with an emphatic ''aaoow'', which is somewhat reminiscent of the deep alarm call of a [[great black-backed gull]] (''Larus marinus'').<ref name= Voous/> They will call mainly from a perch but also sometimes do so in flight.<ref name= Konig/> The ''krooh'' call of the male snowy owl may perform multiple functions such as competitive exclusion of other males and advertising to females.<ref name= Holt/><ref name= Taylor>Taylor, P.S. (1973). ''Breeding behaviour of the Snowy Owl''. Living Bird. 12: 137–154.</ref> The calls of this species may carry exceptionally far in the thin air of Arctic, certainly over more than {{convert|3|km|mi|abbr=on}}, and maybe even to as much {{convert|10|to|11|km|mi|abbr=on}} away.<ref name= Voous/><ref name= Bent/> The female has a similar call to male but can be higher-pitched and/or more guttural as well as single notes which are often disyllabic, ''khuso''.<ref name= Konig/> Female snowy owls have also been known to utter chirps and high screaming notes, similar to those of the nestlings.<ref name= Konig/> Both sexes may at times give a series of clucking, squeals, grunts, hisses and cackles, perhaps such as in circumstances when they are excited.<ref name= Konig/><ref name= Voous/><ref name= Holt/><ref name= Watson>{{cite journal|title=The behaviour, breeding and food-ecology of the Snowy Owl ''Nycea scandiaca''| author=Watson, Adam| year=1957| doi=10.1111/j.1474-919X.1957.tb01959.x| journal=Ibis| volume=99| issue=3| pages =419–462}}</ref> The alarm call is a loud, grating, hoarse ''keeea''.<ref name= Voous/> Another raspier bark is recorded, sometimes called a "watchman's rattle" call, and may be transcribed as ''rick, rick, rick'', ''ha, how, quack, quock'' or ''kre, kre, kre, kre, kre''.<ref name= Sutton/> A female attacking to protect her nest was recorded to let out a crowed ''ca-ca-oh'' call, whilst other owls attacking to protect the nest did a loud version of the typical call while circling before dropping down.<ref name= Taylor/><ref name= Sutton>{{cite journal|doi=10.2307/1364705| last=Sutton | first=George M. | last2=Parmelee | first2=David F. | title=Breeding of the Snowy Owl in Southeastern Baffin Island | journal=The Condor| volume=58 | issue=4 | year=1956 | pages=273–282}}</ref> They may also clap their beak in response to threats or annoyances. While called clapping, it is believed this sound may actually be a clicking of the tongue, not the beak. Though largely only vocal in the breeding season, leading to some erroneous older accounts describing the snowy owl as completely silent, some vocalizations have been recorded in winter in the northern United States.<ref name= Evans/> Initially, the young of the snowy owl have a high pitched and soft begging call which develops into a strong, wheezy scream at around 2 weeks. At the point when the young owls leave the nest around 3 weeks, the shrill squeals they emit may allow the mothers to locate them.<ref name= Parmelee/><ref name= Watson/><ref name= Parmelee2>Parmelee, D. (1992). "Snowy Owl (''Nyctea scandiaca'')". No. 10 in: Poole et al. (1992–1993).</ref> [[File:Juvenile male calling for its mother.jpg|thumb|Juvenile snowy owl, about 12 weeks old]] == Distribution and habitat== ===Breeding range=== The snowy owl is typically found in the northern circumpolar region, where it makes its summer home north of [[60th parallel north|latitude 60° north]] though sometimes down to 55 degrees north.<ref name= Voous/> However, it is a particularly [[nomad]]ic bird, and because population fluctuations in its [[Predation|prey]] species can force it to relocate, it has been known to breed at more southerly latitudes. Although the total breeding range includes a little over {{convert|12000000|km2|sqmi|abbr=on}}, only about {{convert|1300000|km2|sqmi|abbr=on}} have a high probability of breeding, i.e. breeding at no more than 3–9-year intervals.<ref name= Potapov/><ref>{{cite journal|doi=10.1016/j.ecoinf.2014.08.008|title=Discovering and developing primary biodiversity data from social networking sites: A novel approach|year=2014|last1=Barve|first1=Vijay|journal=Ecological Informatics|volume=24|pages=194–199}}</ref> Snowy owls nest in the Arctic [[tundra]] of the northernmost stretches of [[Alaska]], Northern Canada, and [[Palearctic|Eurosiberia]].<ref name= Konig/> [[File:Bobby Tulloch and snowy owl nest site, Fetlar, Shetland, 1967.jpg|thumb|left|[[Bobby Tulloch]], the Shetland [[RSPB]] warden, at the site of the snowy owl nest on the island of [[Fetlar]], Shetland, in August 1967]] Between 1967<ref>{{cite news| title=Snowy Owl with young—an historic photograph | first=Eric | last=Hosking | author-link=Eric Hosking | newspaper=[[The Times]] | location=UK | date=2 August 1967 }}</ref> and 1975, snowy owls bred on the remote island of [[Fetlar]] in the [[Shetland]] Isles north of mainland [[Scotland]], discovered by the Shetland [[RSPB]] warden, [[Bobby Tulloch]].<ref>{{cite news| url=https://www.shetnews.co.uk/2016/11/28/fond-memories-of-the-bobby-the-birdman/ | title=Reviews / Fond memories of the Bobby the birdman | first=Hans J. | last=Marter | newspaper=[[The Shetland News]] | location=UK | date=28 November 2016 | access-date=23 October 2020 }}</ref> Females summered as recently as 1993, but their status in the [[British Isles]] is now that of a rare winter visitor to Shetland, the [[Outer Hebrides]] and the [[Cairngorms]].<ref>[http://news.bbc.co.uk/2/hi/uk_news/scotland/highlands_and_islands/7397993.stm "Hope of first owl chicks in years"], [[BBC News]]. 13 May 2008.</ref><ref>{{cite journal|url=https://www.the-soc.org.uk/files/docs/about-us/publications/scottish-birds/sb-vol15-contents.pdf|author=Marquiss, M., Smith, R. & Galbraith, H. |year=1989|title=Diet of Snowy Owls on Cairn Gorm Plateau in 1980 and 1987|journal= Scottish Birds|volume= 15|issue=4|pages= 180–181}}</ref> Older records show that the snowy owls may have once semi-regularly bred elsewhere in the [[Shetland]]s.<ref>{{cite journal|author=Saxby, H. L. |year=1863|title=Notes on the Snowy Owl|journal= Zoologist |volume=21|pages=8633–8639}}</ref> They range in northern Greenland (mostly [[Peary Land]]) and, rarely in "isolated parts of the highlands", Iceland.<ref name= Konig/><ref name= Voous/><ref name= Potapov/> Thence, they are found breeding at times across northern [[Eurasia]] such as in [[Spitsbergen]] and western and northern [[Scandinavia]]. In Norway, they normally breed in [[Troms og Finnmark]] and seldom down as far south as [[Hardangervidda]] and in Sweden perhaps down to the [[Scandinavian Mountains]] while breeding is very inconsistent in Finland.<ref name= Voous/><ref>Saurola, P. L. (1997). [https://www.fs.usda.gov/treesearch/pubs/15532 ''Monitoring Finnish owls 1982–1996: methods and results'']. United States Department of Agriculture Forest Service General Technical Report NC, pp. 363–380.</ref> They also range in much of northern Russia, including northern [[Siberia]], [[Anadyr Highlands|Anadyr]], [[Koryak Okrug|Koryakland]], [[Taymyr Peninsula]], [[Yugorsky Peninsula]], [[Sakha]] (especially the [[Chukochya River]]) and [[Sakhalin]].<ref name="iucn status 19 November 2021" /><ref name= Konig/><ref name= Voous/> Breeding have also been reported sporadically to the south in the [[Komi Republic]] and even the [[Kama River]] in southern [[Perm Krai]].<ref name= Potapov/> Although considered part of the regular range, the last breeding by snowy owls in the [[Kola Peninsula]] was not since the early 1980s; similarly, breeding maps show the species in [[Arkhangelsk Oblast]] and the [[Pay-Khoy Ridge]] but no breeding records known in at least 30 years in either.<ref>Mineev, O. Y. & Minnev, Y. N. (2005). ''Distribution of owls in North-East European tundra''. In: ''Owls of the Northern Eurasia'' (eds. Volkov S.V., Morozov V.V. & Sharikov A.V.).</ref> They range throughout most of the Arctic [[Island|isles]] of Russia such as [[Novaya Zemlya]], [[Severnaya Zemlya]], [[New Siberian Islands]], [[Wrangel Island]], [[Commander Islands|Commander]] and [[Hall Islands]].<ref name="iucn status 19 November 2021" /><ref name= Konig/><ref name= Voous/> In North America, the breeding range has been known in modern times to include the [[Aleutian islands|Aleutians]] (i.e. [[Buldir Island|Buldir]] and [[Attu Island|Attu]]) and much of northern [[Alaska]], most frequently from the [[Arctic National Wildlife Refuge]] to [[Utqiaġvik, Alaska|Utqiaġvik]], and more sporadically down along the coastal-western parts such as through [[Nome, Alaska|Nome]], [[Hooper Bay, Alaska|Hooper Bay]], the [[Yukon Delta National Wildlife Refuge]], and rarely even south to the [[Shumagin Islands]].<ref name="iucn status 19 November 2021" /><ref name= Voous/> The snowy owl may breed extensively in northern Canada, largely making its home in the [[Arctic Archipelago]].<ref name="iucn status 19 November 2021" /> Their Canadian breeding range can include broadly [[Ellesmere Island]] up to [[Cape Sheridan]], north coastal [[Labrador]], the northern [[Hudson Bay]], perhaps all of [[Nunavut]] (especially the [[Kivalliq Region]]), northeastern [[Manitoba]], both most of northern mainland and insular [[Northwest Territories]] (including the [[River delta|delta]] of the [[Mackenzie River]]) and northern [[Yukon Territory]] (where breeding is mostly confined to [[Herschel Island]]).<ref name="iucn status 19 November 2021" /><ref name= Konig/><ref name= Voous/><ref name= Holt/><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/jrr/v009n03-04/p00060-p00064.pdf|author=Miller, F.L., Russell, R.H. & Gunn, A. |year=1975|title=Distribution and numbers of Snowy Owls on Melville, Eglinton, and Byam Martin Islands, Northwest Territories, Canada|journal=Raptor Research|volume= 9|issue=3–4|pages= 60–64}}</ref> Since breeding and distribution is very small, local and inconsistent in northern Europe, northern Canada and northern Alaska represent the core part of the breeding range for snowy owls along with several parts of northern and northeastern/coastal Russia.<ref name= Potapov/><ref name= Holt/><ref name= Cramp/> ===Regular wintering range=== [[File:Snowy owl Wings 212.jpg|thumb|Wing structure]] During the wintering, many snowy owls leave the dark Arctic to migrate to regions further south. Southern limits of the regular winter range are difficult to delineate given the inconsistency of appearances south of the Arctic.<ref name= Konig/><ref name= Voous/> Furthermore, not infrequently, many snowy owls will overwinter somewhere in the Arctic through the winter, though seldom appear to do so in the same sites where they have bred.<ref name= Potapov/><ref name= Holt/> Due in no small part to the difficulty and hazardousness of observation for biologists during these harsh times, there is very limited data on overwintering snowy owls in the tundra, including how many occur, where they winter and what their ecology is at this season.<ref name= Potapov/><ref name= Holt/> The regular wintering range has at times been thought to include Iceland, Ireland and Scotland and across northern Eurasia such as southern Scandinavia, the [[Baltic islands|Baltics]], central Russia, southwestern [[Siberia]], [[Sakhalin]] southern [[Kamchatka]] and, rarely, north China and sometimes the [[Altai Republic]].<ref name="iucn status 19 November 2021" /><ref name= Konig/><ref name= Holt/><ref name= Cramp/> In North America, they occasionally regularly winter in the Aleutian island chain and do so broadly and with a fair amount of consistency in much of southern Canada, from [[British Columbia]] to [[Labrador]].<ref name= Konig/><ref name= Holt/> Recent research has indicated that snowy owls regularly winter in several of the northern [[Ocean|seas]] during wintertime, following the leads of [[sea ice]] as perching sites and presumably hunting mostly [[seabird]]s in [[polynya]]s.<ref>{{cite journal|doi=10.2307/1366490|jstor=1366490|last1=Irving|first1=Laurence|last2=McRoy|first2=C. Peter|last3=Burns|first3=John J.|title=Birds Observed during a Cruise in the Ice-Covered Bering Sea in March 1968|journal=The Condor|year=1970|volume=72|issue=1|pages=110–112}}</ref><ref>{{cite journal|doi=10.14430/arctic3114|title=Winter Observations of Mammals and Birds, St. Matthew Island|year=1971|last1=McRoy|first1=C. Peter|last2=Stoker|first2=Sam W.|last3=Hall|first3=George E.|last4=Muktoyuk|first4=Edward|journal=Arctic|volume=24}}</ref><ref name= Marine>{{cite journal|doi=10.1111/j.1600-048X.2011.05330.x|title=An avian terrestrial predator of the Arctic relies on the marine ecosystem during winter|year=2011|last1=Therrien|first1=Jean-François|last2=Gauthier|first2=Gilles|last3=Bêty|first3=Joël|journal=Journal of Avian Biology|volume=42|issue=4|pages=363–369}}</ref> In February 1886, a snowy owl landed on the rigging of the [[Nova Scotia]] steamship ''Ulunda'' on the edge of the [[Grand Banks of Newfoundland]], over {{convert|800|km|in|abbr=on}} from the nearest land. It was captured and later preserved at the [[Nova Scotia Museum]].<ref>Conlin, Dan (2 October 2013). [http://marinecurator.blogspot.ca/2013/10/an-owl-oddity.html "An Owl Oddity"], Maritime Museum of the Atlantic.</ref><ref name= Gross1>{{cite journal|doi=10.2307/4080718|jstor=4080718|last1=Gross|first1=Alfred O.|title=Cyclic Invasions of the Snowy Owl and the Migration of 1945-1946|journal=The Auk|year=1947|volume=64|issue=4|pages=584–601}}</ref> Surprisingly, some studies have determined that after a high lemming year in North America, a higher percentage of snowy owls were using marine environments rather than inland ones.<ref>{{cite journal|doi=10.1111/jav.01707|title=Wintering space use and site fidelity in a nomadic species, the snowy owl|year=2018|last1=Robillard|first1=Audrey|last2=Gauthier|first2=Gilles|last3=Therrien|first3=Jean-François|last4=Bêty|first4=Joël|journal=Journal of Avian Biology|volume=49|issue=5}}</ref><ref name= Therrien>{{cite journal|last1=Therrien|first1=Jean-François|title=Winter Use of a Highly Diverse Suite of Habitats by Irruptive Snowy Owls|journal=Northeastern Naturalist|date=March 2017|volume=24|issue=Special Issue 7|pages=B81–B89|doi=10.1656/045.024.s712|s2cid=90013886}}</ref> ===Irruptive range=== Large winter irruptions at temperate latitudes are thought to be due to good breeding conditions resulting in more juvenile migrants.<ref name= Holt/> These result in [[irruptive growth|irruptions]] occurring further south than the typical snowy owl range in some years.<ref name= Santonja>{{cite journal | author1= Santonja, P. |author2= Mestre, I. | author3= Weidensaul, S. | author4= Brinker, D. | author5= Huy, S. |author6= Smith, N. | author7= Mcdonald, T. |author8= Blom, M. | author9= Zazelenchuck, D. |author10= Weber, D. | author11= Gauthier, G. | author12= Lecomte, N. | author13= Therrien, J. |year=2019| title= ''Age composition of winter irruptive Snowy Owls in North America'' | journal=Ibis| volume=161| pages = 211–215| doi= 10.1111/ibi.12647| issue=1| doi-access= free }}</ref> They have been reported, as well as in all northerly states in the contiguous states,<ref>Root, T. R. (1988). ''Atlas of Wintering North American Birds: An Analysis of Christmas Bird Count Data''. University of Chicago Press, Chicago, IL, USA.</ref> as far south as the [[Georgia (U.S. state)|Georgia]], [[Kentucky]], [[South Carolina]], nearly all the [[Gulf Coast of the United States]], [[Colorado]], [[Nevada]], [[Texas]], [[Utah]], California and even Hawaii.<ref name= Voous/><ref name= Bent/><ref>{{cite journal|url=https://www.ksbirds.org/kos/bulletin/Vol64No4.pdf|author1=Robbins, M. B. |author2= Otte, C. |year=2013|title=The irruptive movement of Snowy Owls (''Bubo scandiacus'') into Kansas and Missouri during the winter of 2011–2012|journal= Kansas Ornithological Society Bulletin |volume=64 |issue=4|pages= 41–44}}</ref> In January 2009, a snowy owl appeared in [[Spring Hill, Tennessee|Spring Hill]], Tennessee, the first reported sighting in the state since 1987.<ref>[https://stylingowlish.com/blogs/news/snowy-owl-appears-in-middle-tennessee "Snowy Owl Appears in Middle Tennessee."] ''The Styling Owlish.'' 24 January 2009.{{dead link|date=October 2017}}</ref> Also notable is the mass southern migration in the winter of 2011/2012, when thousands of snowy owls were spotted in various locations across the United States.<ref>Zuckerman, Laura (28 January 2012). [https://www.reuters.com/article/us-owls-migration-idUSTRE80R0MP20120128 ''Snowy owls soar south from Arctic in rare mass migration'']. Reuters</ref> This was then followed by an even larger mass southern migration in 2013/2014 with the first snowy owls seen in Florida for decades.<ref>{{cite web|last=Leung|first=Marlene Leung|title=Snowy owl invasion: Birds spotted as far south as Florida|url=http://www.ctvnews.ca/sci-tech/snowy-owl-invasion-birds-spotted-as-far-south-as-florida-1.1618624|publisher=CTV News|date=5 January 2014}}</ref><ref>{{cite news|last=Schwartz|first=John|title=A Bird Flies South, and It's News|url=https://www.nytimes.com/2014/02/01/us/influx-of-snowy-owls-thrills-and-baffles-birders.html|newspaper=New York Times|access-date=31 January 2014|date=31 January 2014}}</ref> The nature of irruptions is less well-documented in Eurasia, in part due to the paucity of this owl in the European side, but accidental occurrence, presumably during irruptions, has been described in the [[Mediterranean]] area, France, [[Crimea]], the [[Caspian sea|Caspian]] part of Iran, Kazakhstan, northern Pakistan, [[northwestern India]], Korea and Japan.<ref name= Voous/><ref name= Holt/><ref>{{cite journal|doi=10.3838/jjo.36.101|title=Records of ''Nyctea scandiaca'' from Hokkaido, Japan|year=1987|last1=Fujimaki|first1=Yuzo|journal=Japanese Journal of Ornithology|volume=36|issue=2–3|pages=101–103}}</ref> Stragglers may too turn up as far south as the [[Azores]] and Bermuda.<ref name= Konig/> ===Habitat=== [[File:Bubo scandiacus Damon Point 8.jpg|thumb|left|Snowy owls often seek out grassy and open habitats year around.]] Snowy owls are one of the best known inhabitants of the open Arctic [[tundra]]. Frequently, the earth in snowy owl breeding grounds is covered with [[moss]]es, [[lichen]]s and some [[Rock (geology)|rock]]s. Often the species preferentially occurs in areas with some rising elevation such as [[hummock]]s, [[Hillock|knolls]], [[ridge]]s, [[Bank (geography)|bluffs]] and [[Outcrop|rocky outcrops]].<ref name= Konig/><ref name= Voous/> Some of these rises in the tundra are created by [[Till|glacial deposits]].<ref name= Voous/> The ground is usually rather dry in tundra but in some areas of the southern tundra can also be quite [[marsh]]y.<ref name= Voous/> Not infrequently, they will also use areas of varied [[coast]]al habitat, often [[Mudflat|tidal flats]], as a breeding site.<ref name= Konig/><ref name= Voous/><ref name= Murie>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/condor/v031n01/p0003-p0012.pdf|author=Murie, O. J. |title=Nesting of the Snowy Owl |journal=The Condor |year=1929 |volume=31 |issue=1 |pages=3–12 |doi=10.2307/1363262|jstor=1363262 }}</ref> Breeding sites are usually at low elevations, usually less than {{convert|300|m|ft|abbr=on}} above sea level, but when breeding to the south in inland mountains, such as in Norway, they may nest at as high as {{convert|1000|m|ft|abbr=on}}.<ref name= Holt/><ref name= Parmelee/><ref name= Cramp/> Outside the breeding season, snowy owls may habituate nearly any [[Open terrain|open landscape]].<ref name= Konig/> Typically wintering sites are rather windswept with meager cover.<ref name= Hume/> These open areas can include those such as [[Dune|coastal dune]]s, other [[coast]]al spots, [[Shore|lakeshores]], islands, [[moorland]]s, [[steppe]]s, [[meadow]]s, [[prairie]]s, other extensive [[grassland]]s and rather [[shrub]]by areas of the [[Subarctic]]. These may be favored due to their vague similarity to the flat openness of the tundra.<ref name= Voous/><ref name= Hume/> Manmade open sites are now perhaps even more used than natural ones, often agricultural [[Field (agriculture)|field]]s and [[rangeland]], as well as large areas of [[Clearcutting|cleared forests]].<ref name= Holt/><ref name= Kerlinger2>{{cite journal|doi=10.1139/z85-273|title=Distribution and population fluctuations of wintering Snowy Owls (''Nyctea scandiaca'') in North America|year=1985|last1=Kerlinger|first1=P.|last2=Lein|first2=M. Ross|last3=Sevick|first3=Brian J.|journal=Canadian Journal of Zoology|volume=63|issue=8|pages=1829–1834}}</ref><ref name= Doyle>{{cite journal|doi=10.3356/JRR-16-51.1|title=Seasonal Movements of Female Snowy Owls Breeding in the Western North American Arctic|year=2017|last1=Doyle|first1=Frank I.|last2=Therrien|first2=Jean-François|last3=Reid|first3=Donald G.|last4=Gauthier|first4=Gilles|last5=Krebs|first5=Charles J.|journal=Journal of Raptor Research|volume=51|issue=4|pages=428–438|s2cid=4675025}}</ref> During irruption years when they are found in the Northeastern United States, juveniles frequent developed areas including urban areas and [[golf course]]s, as well as the expected [[grassland]]s and [[Agriculture|agricultural areas]] that older birds primarily use.<ref name= Therrien/> On the plains of Alberta, observed snowy owls spent 30% of their time in [[Crop residue|stubble-fields]], 30% in [[summer fallow]], 14% in [[hay]]field and the remainder of the time in [[pasture]], [[Grassland|natural grasslands]] and [[Slough (hydrology)|slough]]s. The agricultural areas, large untouched by the farmers in winter, may have had more concentrated prey than the others in Alberta.<ref name= Lein>{{cite journal|author1=Lein, M.R. |author2 =Webber, G.A.|year=1979|title=Habitat selection by wintering Snowy Owls (''Nyctea scandiaca'')|journal= Canadian Field-Naturalist|volume= 93|issue=2|pages=176–178}}</ref> Perhaps the most consistently attractive habitat in North America to wintering snowy owls in modern times may be airports, which not only tend to have the flat, grassy characteristics of their preferred habitats but also by winter host a particular diversity of prey, both [[Pest (organism)|pests]] which rely on humans as well as wildlife attracted to the extensively grassy and marshy strips that dot the large airport vicinities. For example, [[Logan International Airport]] in [[Massachusetts]] has one relatively one of the most reliable annual populations known in the United States in winter.<ref name= Voous/><ref name= Holt/><ref>{{cite journal|doi=10.2307/3807920|jstor=3807920|title=Raptor and Vole Populations at an Airport|last1=Baker|first1=James A.|last2=Brooks|first2=Ronald J.|journal=The Journal of Wildlife Management|year=1981|volume=45|issue=2|pages=390–396}}</ref> All ages spend a fair amount of their time over water in the [[Bering Sea]], the Atlantic Ocean and even the [[Great Lakes]], mostly on ice floes.<ref name= Weidensaul/> These marine and ocean-like freshwater areas were observed to account for 22–31% of habitat used in 34 radio-tagged American snowy owls over two irruptive years, with the tagged owls occurring a mean of {{convert|3|km|mi|abbr=on}} from the nearest land (while 35–58% used the expected preferred habitats of grassland, pasture and other agriculture).<ref name= Doyle/> ==Behavior== [[File:Bubo scandiacus Delta 6.jpg|thumb|right|Juvenile owls do not mind associating with one another, especially during winter.]] Snowy owls may be active to some extent at both day, from dawn to dusk, and night.<ref name= Konig/> Snowy owls have been seen to be active even during the very brief winter daytime in the northern winter.<ref name= Voous/> During the Arctic summer, snowy owls may tend to peak in activity during the twilight that is the darkest time available given the lack of full nightfall.<ref name= Voous/><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/nab/v027n01/p00011-p00012.pdf|author=Young, C.M. |year=1973|title=The Snowy Owl migration of 1971–72 in the Sudbury region of Ontario|journal= American Birds |volume=27|issue=1|pages= 11–12}}</ref><ref name=shields>{{cite journal|doi=10.2307/3536292}}</ref> Reportedly, the peak time of activity during summer is between 9:00&nbsp;pm and 3:00&nbsp;am in Norway.<ref name= Hagen>Hagen, Y. (1960). ''The Snowy Owl on Hardangervidda in the Summer of 1959''. Papers of The Norwegian State Game Research. 2, No. 7.</ref> The peak time of activity for those owls that once nested on Fetlar was reported between 10:00 and 11:00&nbsp;pm.<ref name= Tulloch>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V61/V61_N03/V61_N03_P119_132_A019.pdf|author=Tulloch, R. J. |year=1968|title=Snowy Owls breeding in Shetland in 1967|journal= British Birds|volume= 61|pages=119–132}}</ref> According to one authority, the least active times are at noon and midnight.<ref name= Watson/> As days become longer near autumn in [[Utqiaġvik, Alaska|Utqiaġvik]], the snowy owls in the tundra become more active around nightfall and can often be seen resting during the day, especially if it is raining.<ref name=shields/> During winter in [[Alberta]], snowy owls were tracked in the daytime, despite being also active at night (as they were deemed too difficult to track). In the study, they were most active during 8:00–10:00&nbsp;am and 4:00–6:00&nbsp;pm and often rested mostly from 10:00&nbsp;am to 4:00&nbsp;pm. The owls were perched for 98% of observed daylight and seemed to time their activity to peak times for rodents.<ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/jfo/v060n01/p0020-p0029.pdf|author1=Boxall, P. C. |author2= Lein, M. R. |year=1989|title=Time budgets and activity of wintering Snowy Owls|journal= Journal of Field Ornithology |volume=60 |issue=1|pages= 20–29}}</ref> The variation of activity is probably in correspondence with their primary prey, the [[lemming]]s, and like them, the snowy owl may be considered [[Cathemerality|cathermal]].<ref name= Konig/><ref name= Voous/><ref name="National Geographic">{{cite web|title=Snowy Owl (Nyctea Scandia)|url=http://animals.nationalgeographic.com/animals/birds/snowy-owl/|website=animals.nationalgeographic.com|publisher=National Geographic|date=11 November 2010}}</ref> This species can withstand extremely cold temperatures, having been recorded in temperatures as low as minus 62.5 [[Celsius|degrees Celsius]] with no obvious discomfort and also withstood a 5-hour exposure to minus 93 degrees Celsius but may have struggled with oxygen consumption by the end of this period. The snowy owl has perhaps the second lowest [[thermal conduction]] to the plumage on average of any bird after only the [[Adelie penguin]] (''Pygoscelis adeliae'') and rivals the best insulated mammals, such as [[Dall sheep]] (''Ovis dalli'') and [[Arctic fox]], as the best insulated polar creature.<ref name= Voous/><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/condor/v057n06/p0362-p0365.pdf|author=Irving, L. |title=Nocturnal decline in the temperature of birds in cold weather|doi=10.2307/1364794}}</ref> Presumably as many as 7 rodents would need to be eaten daily to survive an extremely cold winter's day.<ref name= Voous/> Adults and young both have been seen to shelter behind rocks to shield themselves from particularly harsh winds or storms.<ref name= Holt/> Snowy owls often spending a majority of time on the ground, perched mostly on a slight rise of elevation.<ref name= Konig/> It has been interpreted from the morphology of their skeletal structure (i.e. their short, broad legs) that snowy owls are not well-suited to perching extensively in trees or rocks and prefer a flat surface to sit upon.<ref name= Potapov/> However, they may perch more so in winter though do so only mainly when hunting, at times on [[hummock]]s, [[Fence]]posts, [[telegraph pole]]s by roads, [[Radio tower|radio]] and [[transmission tower]]s, [[Hay]]stacks, [[chimney]]s and the roofs of houses and large buildings.<ref name= Voous/> Rocks may be used as perches at times in all seasons.<ref name= Voous/> Though often relatively sluggish owls, like most related species, they are capable of sudden dashing movements in various contexts.<ref name= Potapov/> Snowy owls can walk and run quite quickly, using outstretched wings for balance if necessary.<ref name= Konig/> This owl flies with fairly rowing wingbeats, occasionally interrupted by gliding on stretched wings. The flight is fairly buoyant for a ''Bubo'' owl.<ref name= Konig/><ref name= Holt/> When displaying, the male may engage in an undulating flight with interspersed wingbeats and gliding in a slight dihedral, finally dropping rather vertically to the ground.<ref name= Konig/> They are capable for swimming but do not usually do so. Some seen to be swimming were previously injured but young have been seen to swim into water to escape predators if they cannot fly yet. They will also drink when unfrozen water is available.<ref name= Holt/><ref name= Tulloch/><ref>Mebs, T. & Scherzinger, W. (2000). ''Snowy Owl''. In: ''Die eulen Europa: biolgie, kennzeichen, bestande'', edited by T. Mebs and W. Scherzinger, 167–183. Stuttgart: Franckh-Kosmos Verlags-Gmbh and Co.</ref> Snowy owl mothers have been observed to [[Preening (bird)|preen]] their young in the wild, while pairs in captivity have been observed to allopreen.<ref name= Watson/> In the period leading up to breeding, snowy owls switched regularly between searching (for nesting grounds) and loafing, often searching less when snow cover was less extensive.<ref>Therrien, J. F., Pinaud, D., Gauthier, G., Lecomte, N., Bildstein, K. L., & Bety, J. (2015). ''Pre-breeding prospecting behaviour of snowy owls'' (data from Therrien et al. 2015)-reference-data.</ref> [[File:A Snowy Owl in Flight David Hemmings.jpg|thumb|left|Snowy owls are often somewhat ponderous in movements but can be surprisingly and suddenly fast on the wing.]] Snowy owls will fight with conspecifics in all seasons occasionally but this is relatively infrequent during breeding and rarer still during winter. Dogfights and talon interlocking may ensue if the fight between two snowy owls continues to escalate.<ref name= Evans/><ref name= Watson/><ref name= Taylor/> A study determined that snowy owls are able to orient the whitest parts of their plumage towards the sun, spending about 44% of time oriented as such during sunny days and much less on cloudy days. Some authors interpret this as a presumed signal to conspecifics, but [[thermoregulation]] could also be a factor.<ref>Bortolotti, G. R., Stoffel, M. J., & Galvan, I. (2011). ''Wintering Snowy Owls Bubo scandiacus integrate plumage colour, behaviour and their environment to maximize efficacy of visual displays''. Ibis, 153(1), 134–142.</ref><ref>{{cite journal |author1= Wiebe, K. L. |author2= Chang, A. M. | year=2018| title= ''Seeing sunlit owls in a new light: orienting Snowy Owls may not be displaying.'' | journal=Ibis| volume=160| pages=62–70| doi=10.1111/ibi.12533| issue=1}}</ref> It is known that during winter in Alberta that female snowy owls are territorial towards one another and may not leave an area for up to 80 days but males are nomadic, usually only staying 1–2 days in an area (seldom to 3–17 days). The females spent on average seven times as long in a given area than did males.<ref name= Boxall>Boxall, P.C. & Lein, M.R. (1982). ''Are owls regular? An analysis of pellet regurgitation times of Snowy Owls in the wild''. Raptor Research. 16(3): 79–82.</ref> During threat displays, individuals will lower the front of the body, stretch the head low and forward, with partially extended wings and feathers on the head and raise their back.<ref name= Watson/> If continuously threatened or cornered, the posture in the threat display may become still more contoured and, if pressed, the owl will like back and attempt to slash with its large talons. The threat displays of males are generally more emphatic than those of females.<ref name= Holt/><ref>Kaufman, K. (1996). ''Lives of North American Birds''. Houghton Mifflin Company, Boston & New York.</ref> Although snowy owls have been considered as semi-colonial, they do not appear to fit this mold well. Nesting sites can be loosely clustered but this is a coincidental response to concentrated prey and each pair tends to be somewhat intolerant of each other.<ref name= Holt/><ref name= Hart>Hart, H. C. (1880). ''Notes on the ornithology of the British Polar Expedition, 1875-6''. Zoologist 4:121–129.</ref><ref>Brandt, H. (1942). ''Alaska Bird Trails: An Expedition by Dog Sled to the Delta of the Yukon River at Hooper Bay''. The Bird Research Foundation, Cleveland, OH, USA.</ref><ref>Dorogoi, I.V. (1990). ''[Factors of communal breeding of the Snowy Owls (Nyctea scandiaca) and Anseriformes birds at the Vrangel Island]''. Ornitologiya. 24: 26–33. In Russian with English summary.</ref> During winter, snowy owls are usually solitary but some [[Aggregation (ethology)|aggregation]]s have been recorded, especially nearer the Arctic when more narrow food selection can lead to up to 20–30 owls gathering in an area of about {{convert|20|to|30|ha|acre|abbr=on}}.<ref name= Holt/><ref name= Pitelka2>Pitelka, F. A., Tomich, P. Q. & Treichel, G.W. (1955). ''Ecological relations of jeagers and owls as Lemming predators near Barrow, Alaska''. Ecological Monographs 25: 85–117.</ref> Congregations were also recorded in the winter in Montana, where 31–35 owls wintered in a {{convert|2.6|km2|sqmi|abbr=on}} area, owls mostly grouped in loose aggregations of 5–10 owls each or occasionally side-by-side or about {{convert|20|m|ft|abbr=on}} apart.<ref name= Holt2>Holt, D. W. & Zetterberg, S. A. (2008). ''The 2005 to 2006 Snowy Owl irruption migration to western Montana''. Northwestern Naturalist 89 (3):145–151.</ref> In extreme cases in Utqiaġvik, the owls may have exceptionally close active nests that may be down to only {{convert|800|to|1600|m|ft|abbr=on}} apart.<ref name= Pitelka/> Juvenile males appear to be especially prone to loose associations with one another, appearing to be non-territorial and able to hunt freely in front of one another.<ref name= Holt/> In a {{convert|213|km2|sqmi|abbr=on}} area in and around Utqiaġvik, productive years may have about 54 nests while none may be found in poor years.<ref name= Holt/> Utqiaġvik may have about 5 owls in early summer every {{convert|1.6|km|mi|abbr=on}}, have a nest spacing of {{convert|1.6|to|3.2|km|mi|abbr=on}} and the owls territory size is about {{convert|5.2|to|10.2|km2|sqmi|abbr=on}}.<ref name= Holt/> In [[Churchill, Manitoba]], nest spacing averaged about {{convert|3.2|km|mi|abbr=on}}.<ref name= Shelford>Shelford, V. E. (1943). ''The abundance of the Collared Lemming (Dicrostonyx groenlandicus (TR) VAR. Richardsoni Mer.) in the Churchill area, 1929 to 1940''. Ecology 24 (4):472–484.</ref> In [[Southampton Island]] in a year when the owls nested there, nest spacing averaged {{convert|3.5|km|mi|abbr=on}}, with the closest two {{convert|1|km|mi|abbr=on}} apart and density per nest was {{convert|22|km2|sqmi|abbr=on}}.<ref>Parker, G. R. (1974). ''A population peak and crash of lemmings and Snowy Owls on Southampton Island, Northwest Territories''. Canadian Field-Naturalist. 88(2): 151–156.</ref> In Nunavut, densities could go from 1 owl per {{convert|2.6|km2|sqmi|abbr=on}} in a productive year to 1 owl per {{convert|26|km2|sqmi|abbr=on}} in a poor year and from 36 nests in a {{convert|100|km2|sqmi|abbr=on}} area to none at all.<ref name= Manning>Manning, T. H., Höhn, E. O. & MacPherson, A. H. (1956). ''The birds of Banks Island''. National Museum of Canada Bulletin 143, Biological Series 48.</ref><ref>Vaughn, R. (1992). ''In search of Arctic birds''. London: T & AD Poyser, Ltd.</ref> Owl density on Wrangel Island in Russia was observed be a single bird each {{convert|0.11|to|0.72|km2|sqmi|abbr=on}}.<ref name= Menyushina>Menyushina, I. E. (1997). ''Snowy Owl (Nyctea scandiaca) reproduction in relation to lemming population cycles on Wrangel Island''. In: ''Biology and conservation of owls of the Northern Hemisphere: 2nd International Symposium'', edited by J. R. Duncan, D. H. Johnson and T. H. Nicholls, 572–582. St. Paul: U.S. Dept. of Agriculture, Forest Service, North Central Forest Experiment Station.</ref> The first known study of winter territories took place in [[Horicon Marsh]] where owls ranged from {{convert|0.5|to|2.6|km2|sqmi|abbr=on}} each.<ref name= Keith/> In [[Calgary, Alberta]], mean territory size of juvenile females in winter was {{convert|407.5|ha|acre|abbr=on}} and adult females was {{convert|195.2|ha|acre|abbr=on}}.<ref name= Boxall/> Wintering owls in central Saskatchewan were radio-monitored, determining that 11 males had an average range of {{convert|54.4|km2|sqmi|abbr=on}}, while that of 12 females was {{convert|31.9|km2|sqmi|abbr=on}} with the combined average being {{convert|53.8|km2|sqmi|abbr=on}}.<ref>Chang, A. M., & Wiebe, K. L. (2018). ''Movement patterns and home ranges of male and female Snowy Owls (Bubo scandiacus) wintering on the Canadian prairies''. Canadian Journal of Zoology, 96(6), 545–552.</ref> [[File:Bubo scandiacus Delta 4.jpg|thumb|left|Snowy owls are usually awake, aware and not infrequently active during daytime.]] ===Migration=== It is fair to say that the snowy owl is a partial, if fairly irregular, [[Bird migration|migrant]], having a very broad but patchy wintering range.<ref name= Konig/> 1st year birds tend to disperse farther south in winter than older owls with males wintering usually somewhat more to the south than females of equivalent ages, adult females often wintering the farthest north.<ref name= Voous/><ref name= Scandinavica>Kerlinger, P. & Lein, M.R. (1986). ''Differences in winter range among age-sex classes of Snowy Owls Nyctea scandiaca in North America''. Ornis Scandinavica. 17(1): 1–17.</ref> The snowy owl likely covers more ground than almost any other owl in movements but many complex individual variations are known in movements, and they often do not take the traditional north–south direction that might be assumed.<ref name= Holt/> Migratory movements appear to be somewhat more common in America than in Asia.<ref name= Konig/> A study of wintering owls in the [[Kola Peninsula]] determined that the mean date of arrival of owls was 10 November with a departure date of 13 April, covering an average of {{convert|991|km|mi|abbr=on}} during the course of the wintering period and clustering where [[Ptarmigan|prey]] was more concentrated.<ref>Øien, I. J., Aarvak, T., Jacobsen, K. O., & Solheim, R. (2018). ''Satellite Telemetry Uncovers Important Wintering Areas for Snowy Owls On the Kola Peninsula, Northwestern Russia''. Орнитология, 42, 42–49.</ref> Some variety of movements recorded each autumn and snowy owls winter annually in plains of [[Siberia]] and Mongolia and [[prairie]]s and [[marsh]]lands of Canada.<ref name= Voous/> The [[Great Plains]] area of southern Canada host wintering snowy owls about 2 to 10 times more frequently than other areas of the continent.<ref name= Holt/> Some weak correlation has made with individuals having some level of fealty to certain wintering sites.<ref>Oeming, A. F. (1957). ''Notes on the Barred Owl and the Snowy Owl in Alberta''. Blue Jay 15:153–156.</ref><ref>Follen, D. & Luepke, K. (1980). ''Snowy Owl recaptures''. Inland Bird Banding 52: 60.</ref> Wintering snowy owls, a total of 419, recorded in [[Duluth, Minnesota]] from 1974 to 2012 would occur in larger numbers in years where [[Brown rat|rats]] were more plentiful. The amount of individual returns among 43 Duluth-wintering owls was fairly low in subsequent winters (8 for 1 year, a small handful in the next few years, and 9 in non-consecutive years).<ref name= Holt/> Sometimes surveys appeared to reveal hundreds of wintering snowy owls on coastal sea ice during an irruptive year.<ref name= Voous/><ref name= Marine/> Three siblings that hatched in same nest in [[Cambridge Bay]] were recovered in drastically different spots at least a year later: one in eastern [[Ontario]], one in [[Hudson Bay]] and one in [[Sakhalin Island]].<ref name= Parmelee/> A nestling banded in [[Sogn og Fjordane|Hordaland]] was recovered {{convert|1380|km|mi|abbr=on}} to the northeast in [[Finnmark]].<ref name= Voous/> In the [[Logan Airport]], 17 of 452 owls were recorded to return, eleven the following year, three 2 years later, and then singles variously 6, 10 and 16 years later.<ref name= Holt/> A banded female from Utqiaġvik was recorded to migrate over {{convert|1928|km|mi|abbr=on}} along seacoast down to Russia, returning over {{convert|1528|km|mi|abbr=on}} and covering at least {{convert|3476|km|mi|abbr=on}} in total. Another banded young female from Utqiaġvik went to the same Russian areas, returned to Utqiaġvik and then onto [[Victoria Island (Canada)|Victoria Island]], but did appear to breed, while another also covered a similar route but ended up nesting on [[Banks Island]]. Another female migrated to the [[Canada–United States border]], then moved back to the [[Gulf of Alaska]], then to winter in the same border areas and then finally to both Banks and Victoria Island.<ref name= Holt/> Snowy owls from the Canadian Arctic were monitored to have covered an average of {{convert|1100|km|mi|abbr=on}} in one autumn then covered an average of {{convert|2900|km|mi|abbr=on}} a year later.<ref name= Therrien2>Therrien, J.-F., Fitzgerald, G., Gauthier G. & Bêty, J. (2011). ''Diet-tissue discrimination factors of carbon and nitrogen stable isotopes in blood of Snowy Owl (Bubo scandiacus)''. Canadian Journal of Zoology 89 (4): 343–347.</ref> In late winter, owls from the same area were found to have covered a mean of {{convert|4093|km|mi|abbr=on}} of ground in the tundra and spent a mean of 108 days, apparently searching for a suitable nesting situation the entire time.<ref>Therrien, J.-F. , Gauthier, G., Pinaud, D. & Bêty, J. (2014). ''Irruptive movements and breeding dispersal of Snowy Owls: a specialized predator exploiting a pulsed resource''. Journal of Avian Biology. 45(6): 536–544.</ref> In no fewer than 24 winters between 1882 and 1988, large numbers have occurred in Canada and the United States. These were [[Irruptive growth|irruption]] years.<ref name= Voous/> Record breeding irruptive years were recorded in the winters of 2011–2012 and 2014–2015.<ref name= Holt/> In the 1940s, it was calculated that the mean gape in time between large irruptions was 3.9 years.<ref name= Gross1/> Southbound movements as such are much more conspicuous after peak vole years, once thought to be separated by periods of around 3–7 years.<ref name= Voous/><ref>{{cite journal|author=Snyder, L. L. |year=1943|title=The Snowy Owl migration of 1941–42|journal= Wilson Bulletin |volume=55 |issue=1|pages=8–10|jstor=4157203|url=https://sora.unm.edu/sites/default/files/journals/wilson/v055n01/p0008-p0010.pdf}}</ref><ref>{{cite journal|doi=10.2307/4079810}}</ref><ref name=chitty/> However, more extensive research has weakened the argument that irruptions are entirely food-based and the data indicates that irruptive movements are far from predictable. This is because a statewide survey in Alaska found no statewide synchrony in lemming numbers. Therefore, rather than decline of lemmings, it is the successful productivity of several pairs that plays the role, resulting in a large number of young owls that then irrupt. However, the snowy owls cannot breed in high numbers unless lemmings are widely available on the tundra.<ref name= Holt/><ref name= Kerlinger2/><ref name= Gross/><ref>Pitelka, F. A. & Batzli, G. O. (1993). ''Distribution, abundance, and habitat use by lemmings on the north slope of Alaska''. In: ''The biology of lemmings'', edited by N. C. Stenseth and R. A. Ims, 213–236. London: Academic Press.</ref><ref name="Krebs">Krebs, C. J. (1993). ''Are lemmings large Microtus or small reindeer? A review of lemming cycles after 25 years and future recommendations for future work''. In: ''The biology of lemmings'', edited by N. C. Stenseth and R. Ims, 247–260. London: Academic Press for the Linnean Society of London.</ref> This connection of irruptions to high years of productivity was confirmed in a study by Robillard et al. (2016).<ref>{{cite journal|pmid=26920901|doi=10.1007/s00442-016-3588-3}}</ref> About 90% of the snowy owls seen in irruptive years from 1991 to 2016 that were ageable were identified as juveniles.<ref name= Santonja/> ==Feeding== ===Hunting techniques=== [[File:Harfang en vol 1.jpg|thumb|right|A snowy owl engaging in the "sweep" hunting method.]] Snowy owls may hunt at nearly at any time of the day or night, but may not attempt to do so during particularly severe weather.<ref name= Holt/> During the [[summer solstice]], the owls appear to hunt during "theoretical nightfall".<ref name= Holt/> [[Night-vision device]]s have allowed biologists to observe that snowy owls hunt quite often during the extended nighttime during the northern winter.<ref name= Potapov/><ref name= Holt/> Prey are both taken and eaten on the ground.<ref name= Konig/> Snowy owls, like other carnivorous birds, often swallow their small prey whole.<ref name= Konig/> Strong stomach juices digest the flesh, while the indigestible bones, teeth, fur, and feathers are compacted into oval pellets that the bird regurgitates 18 to 24 hours after feeding. Regurgitation often takes place at regular perches, where dozens of pellets may be found. Biologists frequently examine these pellets to determine the quantity and types of prey the birds have eaten. When large prey are eaten in small pieces, pellets will not be produced.<ref>[http://www.owlpages.com/owls.php?genus=Bubo&species=scandiacus Snowy Owl — ''Bubo scandiacus'', formerly ''Nyctea scandiaca'']. owlpages.com</ref> Larger prey is often torn apart, sometimes include removal of the head, with the large muscles, such as the [[humerus]] or [[Thorax|breast]], typically eaten first.<ref name= Holt/> The scattering of remains that results from the increment feeding on larger prey is thought to result in under-identification of them compared to smaller prey items.<ref>{{cite journal|title=A taphonomic investigation of small vertebrate accumulations produced by the snowy owl (''Bubo scandiacus'') and its implications for fossil studies|doi=10.1016/j.palaeo.2018.10.018}}</ref> The aptitude for hunting by day, hunting from the ground and hunting in almost always completely open and treeless areas are the primary ways in which the snowy owl differs in hunting from other ''Bubo'' owls. Otherwise, the hunting habits are similar.<ref name= Holt/><ref name= Johnsgard>[[Paul Johnsgard|Johnsgard, P. A.]] (1988). [https://digitalcommons.unl.edu/johnsgard/46/ ''North American owls: biology and natural history'']. Smithsonian Institution.</ref> It is thought, due to their less refined hearing compared to other owls, prey is usually perceived via vision and movement.<ref name= Voous/><ref name= Holt/> Experiments indicate that snowy owls can detect prey from as far as {{convert|1.6|km|mi|abbr=on}} away. Snowy owls generally use a rise or, occasionally, a perch while hunting.<ref name= Konig/> 88% of observed 34 hunts in Utqiaġvik were undertaken from an elevated watch-site (56% mounds or rises, 37% [[telephone pole]]s).<ref name= Holt/> Their hunting style may recall that of [[Buteo|buzzard]]s, with the hunting owl sitting rather low and perching immobile for a long spell.<ref name= Hume/> Although their usual flight is a slow, deliberate downbeat on the broad, fingered wings, when prey is detected from their perch, flight may undertaken with a sudden, surprisingly quick accelerated style with interspersed wing beats.<ref name= Hume/><ref>{{cite journal|author=Hohn, E. O. |year=1973|title=Winter hunting of Snowy Owls in farmland|journal= Canadian Field-Naturalist|volume= 87 |issue=4|pages= 468–469}}</ref> In Utqiaġvik, snowy owls may most frequently engage in a brief pursuit hunting style.<ref name= Holt/> In high winds capable of keeping their bulk aloft, snowy owls may too engage in a brief [[Levitation|hovering]] flight before dropping onto prey.<ref name= Watson/> When hunting fish, apparently, some snowy owls will hover in a style reminiscent of the [[osprey]] (''Pandion haliaetus''), although in at least one other case a snowy owl was observed to capture fish by lying on its belly upon a rock by a fishing hole.<ref name= Audubon>Audubon, J. J. (1840). ''The Birds of America''. Dover Publications, Inc., New York, NY, USA.</ref> A dashing stoop or pounce down onto their prey, ending in a high-impact "wallop", is fairly commonly recorded.<ref name= Holt/><ref name= Hume/> Another common technique is the "sweep", wherein they fly by and grasp the prey while continuing to fly.<ref name= Holt/><ref>{{cite journal|author=Dancey, H.E. |year=1983|title=Winter foraging habits of a Snowy Owl|journal= Indiana Audubon Quarterly|volume= 61|issue=4|pages= 136–144}}</ref> In winter, snowy owls have been shown to be able to "snow plunge" to capture prey in the [[Subnivean climate|subnivean zone]], under at least {{convert|20|cm|in|abbr=on}} of snow. Perhaps least frequently, snowy owls may pursue their on foot, in doing so never taking wing.<ref name= Holt/> Snowy owls have been known to capture [[Bird migration|night-migrating]] [[passerine]]s and [[shorebird]]s, sometimes perhaps on the wing, as well as large and/or [[Bird of prey|potentially dangerous]] birds that were caught in air by snowy owls during daylight.<ref name= Holt/> On the wing pursuits against other various other carnivorous birds are sometimes undertaken as well to [[Kleptoparasitism|kleptoparasitize]] the prey caught by the other birds.<ref name= Holt/><ref>Duffy, D. C., Beehler B. & Haas, W. (1976). ''Snowy Owl steals prey from Marsh Hawk''. Auk 93 (4): 839–840.</ref> Few variations of hunting technique were observed in winter observations from [[Alberta]], almost all of the hunts being with the sit-and-wait method (also known as still-hunts). Adult females in Alberta had a considerably better hunting rate than juvenile females.<ref name= Boxall2>{{cite journal|doi=10.14430/arctic2326|title=Feeding ecology of Snowy Owls (''Nyctea scandiaca'') wintering in S. Alberta}}</ref> Much as in Alberta, in [[Syracuse, New York]], 90% of 51 hunts were still-hunting, with the sweep variant used after perch departure in 31% of hunts and the pounce method in 45% of hunts. The Syracuse-wintering owls used tall perches, a mixture of manmade objects and trees of around {{convert|6|m|ft|abbr=on}} high, in nearly 61% of hunts, while nearly 14% were from low perches (i.e. fence-posts, snow banks and scrap piles) about half as high as the tall perches and started from a ground position nearly 10% of the time.<ref name= Winter>Winter, R. E. (2016). ''Hunting Behaviors and Foraging Success of Winter Irruptive Snowy Owls in New York''. SUNY College of Environmental Science and Forestry, Thesis.</ref> In Sweden, males hunted from a perch more so than did females and adults both focused on significantly smaller prey (small [[mammal]]s) and may have had more success hunting than juvenile snowy owls.<ref name= Lind/> Some snowy owls can survive a fast for up to about 40 days off of [[Fatty acid metabolism|fat reserves]].<ref name= Hume/> These owls were found to have extremely thick [[Subcutaneous tissue|subcutaneous fat deposits]] of around {{convert|19|to|22|mm|in|abbr=on}} and it is likely owls that overwinter in the Arctic rely heavily on these to survive during this scarce time, in combination with lethargic, energy-conserving behavior. Snowy owls may not infrequently exploit prey inadvertently provided or compromised by human activities, including ducks injured by [[Hunting|duck hunters]], [[Red phalarope|birds]] maimed by [[Antenna (radio)|antenna]] wires, various animals caught in human [[Trapping|traps]] and [[trapline]]s as well as [[Domestication of animals|domestic]] or wild prey being bred or farmed by humans in enclosures.<ref name= Watson/><ref name=Wiggins/><ref>Brooks, W. S. (1915). ''Notes on birds from east Siberia and Arctic Alaska''. Bulletin of the Museum of Comparative Zoology 59:361–413.</ref><ref>Nagell, B. & Frycklund, I. (1965). ''The irruption of the Snowy Owl (Nyctea scandiaca) in Scandinavia in the winters of 1960–1963 and notes on its behavior''. Vår Fågelvärld 24 (1): 26–55.</ref><ref>King, B., Nayler, F. & Wardle, F. (1966). ''Feeding and resting behavior of a Snowy Owl in Scilly''. British Birds 59 (3): 108.</ref><ref name= Robertson>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/jrr/v037n02/p00164-p00166.pdf|author1=Robertson, G. J. |author2=Gilchrist, H. G. |year=2003|title=Wintering Snowy Owls feed on sea ducks in the Belcher Islands, Nunavut, Canada|journal= Journal of Raptor Research |volume=37 |issue=2|pages= 164–166}}</ref> A wide variety of accrued reports show that the snowy owl that [[Scavenger|scavenging]] on [[carrion]] is not uncommon (despite having once been thought to be very rare in all owls), including instances of [[reindeer]] (''Rangifer tarandus'') body parts brought to nests and owls following [[polar bear]]s to secondarily feed on their kills. Even huge [[marine mammal]]s such as [[walrus]] (''Odobenus rosmarus'') and whales can be fed upon by these owls when the opportunity occurs.<ref name= Holt/><ref>{{cite journal|doi=10.3356/0892-1016-53.4.410}}</ref> Snowy owls produce a [[Pellet (ornithology)|pellet]] that in different areas averages a median of about {{convert|80|x|30|mm|in|abbr=on}}, averaging up to {{convert|92|mm|in|abbr=on}} in length as in Europe.<ref name= Cramp/><ref name= Detienne/><ref name= Patterson/><ref name= Hagen/> ===Prey spectrum=== [[File:Snowy Owl (240865007).jpeg|thumb|left|A snowy owl flying with an unidentified prey item in winter.]] The snowy owl is primarily a hunter of [[mammal]]s.<ref name= Konig/> Most especially, they often live off of the northerly [[lemming]]s.<ref name= Konig/><ref name= Sutton/><ref name= Watson/> Sometimes other similar rodents like [[vole]]s can also be found frequently in the snowy owl's foods.<ref name= Konig/> It is [[r/K selection theory|R-selected]], meaning that it is an opportunistic breeder capable of taking advantage of increases in prey numbers and diversity, despite its apparent specialization.<ref name= Potapov/> Birds are commonly taken as well, and may regularly include [[passerine]]s, northern [[seabird]]s, [[ptarmigan]] and ducks, among others.<ref name= Konig/> Sometimes infrequent consumption of other prey such as [[beetle]]s, [[crustacean]]s and occasionally [[amphibian]]s and fish is reported (of these only fish are known to have been identified to prey species).<ref name= Konig/><ref name= Bent/><ref name= Detienne>{{cite journal|doi=10.3356/JRR-07-41.1}}</ref> All told, more than 200 prey species have been known to be taken by snowy owls around the world.<ref name= Voous/><ref name= Potapov/><ref name= Holt/> Generally, like other large owls (including even bigger owls like the [[Eurasian eagle-owl]]), prey selection tends toward quite small prey, usually small [[mammal]]s, but they can alternate freely with prey that is much larger than typical given the opportunity or even bigger than themselves, including relatively large mammals and several types of large bird of almost any age.<ref name= Voous/><ref name= Holt/><ref name= Marti>Marti, C. D., Korpimäki, E., & Jaksić, F. M. (1993). "Trophic structure of raptor communities: a three-continent comparison and synthesis". In ''Current ornithology'' (pp. 47–137). Springer, Boston, MA.</ref> One study estimated for the [[biome]]s of [[Alaska]] and Canada, mean prey sizes for snowy owls were {{convert|49.1|g|oz|abbr=on}}, in [[western United States|western North America]], the mean prey size was {{convert|506|g|lb|abbr=on}} and in [[eastern United States|eastern North America]] was {{convert|59.7|g|oz|abbr=on}}, while the mean prey size in northern [[Fennoscandia]] was similar (at {{convert|55.4|g|oz|abbr=on}}). The mean number of prey species for snowy owls per biome ranged from 12 to 28.<ref name= Marti/> The opportunistic nature of snowy owls has long been known during their primarily winter observed feeding habits (leading to their unpopular nature and frequent persecution well into the 20th century).<ref name= Holt/><ref name= Bent/><ref name= Detienne/><ref name= Robinson>Robinson, M. & Becker, C.D. (1986). ''Snowy Owls on Fetlar''. British Birds. 79(5): 228–242.</ref> ===Summer diet=== [[File:Lemmuslemmus.jpg|thumb|right|[[Lemming]]s such as [[Norway lemming]]s are the primary prey of breeding snowy owls.]] The snowy owl's biology is closely tied to the availability of [[lemming]]s. These herbivorous rodents are largish members of the vole clan that are the predominant mammal of the tundra ecosystem alongside the reindeer and probably make up the majority of the mammalian [[biomass]] of the ecosystem. Lemmings are key architects of the soil, [[Topography|microtopography]] and plant life of the entire tundra.<ref>McKendrigk, J. D., Batzli, G. O., Everett, K. R., & Swanson, J. C. (1980). ''Some effects of mammalian herbivores and fertilization on tundra soils and vegetation''. Arctic and Alpine Research, 12(4), 565–578.</ref><ref name="Shelford" /><ref name="Krebs" /><ref>Fitzgerald, B.M. (1981). Predatory birds and mammals. In Tundra ecosystems: a comparative analysis (Eds L.C. Bliss, 0.W. Heal & J.J. Moore), pp. 485–508. Cambridge University Press, Cambridge.</ref> In the American lower Arctic areas, [[True lemming|brown lemming]] of the ''Lemmus'' genus are predominant and tend to be found in lower, wetter habitats (feeding by preference on grasses [[sedge]]s and [[moss]]es) while [[collared lemming]]s of the ''Dicrostonyx'' genus were in more arid, often higher elevation habitats with [[heath]]land and ate by preference [[willow]] [[Leaf|leaves]] and [[forb]]s.<ref>{{cite journal|doi=10.2307/1550496}}</ref> The southerly brown lemmings behave differently than more northern collared lemming type, increasing almost limitlessly within preferred habitat whereas the collared type tends to spread to suboptimal habitats and therefore does not appear reach the high regional densities of the brown.<ref name= Voous/> Authorities now generally agree that there appears to be no synchrony between the brown and collared lemmings and the feeding access of snowy owls is irregular as a result, but snowy owls can likely alternate between the two lemming types as one or the other increases as they nomadically use different parts of the Arctic. It is possible that the rare coincidental mutual peak of both lemming types within a year results in the erratic high productivity that results in irruptions.<ref name= Voous/><ref name= Holt/> Within individual Arctic lemming species, historically, populations can vary in rough 4- to 5-year trends.<ref name= Hume/> As a result, in areas such as [[Banks Island]], the breeding rate of snowy owls can vary within a decade by about tenfold.<ref name= Voous/><ref name= Hume/> Weights of lemmings taken can range from {{convert|30|to|95|g|oz|abbr=on}} on [[Baffin Island]], while those taken in Utqiaġvik averaged {{convert|70.3|and|77.8|g|oz|abbr=on}} in female and male lemming, respectively.<ref name= Holt/><ref name= Watson/> It was estimated based on captive daily food intake that a snowy owl may consume about {{convert|326|g|oz|abbr=on}} of lemmings a day, though other estimates using voles show a daily need for about {{convert|145|to|150|g|oz|abbr=on}}.<ref name= Seidensticker/><ref name= Pitelka/><ref name= Detienne/> On [[Southampton Island]], 97% of the diet was lemmings.<ref name= Parker>{{cite journal|author=Parker, G.R. |year=1974|title=A population peak and crash of lemmings and Snowy Owls on Southampton Island, Northwest Territories|journal= Canadian Field-Naturalist|volume= 88|issue=2|pages=151–156}}</ref> A very similar number of lemmings (nearly 100%) were found over 25 years of study in Utqiaġvik, amongst 42,177 cumulative prey items.<ref name= Holt/> Of 76 lemmings that could be identified to sex at a [[Hoarding (animal behavior)|cache]], male lemmings were found in the cache twice as often as female lemmings.<ref name= Pitelka/> While initial findings indicated on [[Wrangel Island]] that female lemmings outnumbered males in prey remains, to the contrary osteology indicated that, like Utqiaġvik, males were more often taken. However, the slightly larger, slower-moving females may be preferred when available.<ref name= Krechmar>Krechmar, A.V. & Dorogoy, I.V . (1981). "Snowy Owl (''Nyctea scandiaca'')". In: ''Ecology of mammals and birds in Wrangel Island''. Vladivostok: DVNZ AN SSSR: pp. 56–81.</ref> In some areas, snowy owls can breed where lemmings are uncommon to essentially absent.<ref name= Holt/> Even in Utqiaġvik, where the diet is quite homogenously based in lemmings, the hatching of [[passerine]]s, [[shorebird]]s and [[waterfowl]] can provide a key resource when lemmings are not found regularly and may be the only means by which the young can survive at such lean times.<ref name= Holt/> In the [[Nome, Alaska]] area, the locally nesting snowy owls reportedly switched from lemmings to [[ptarmigan]]s when the latter's chicks hatched.<ref name= Dufresne>{{cite journal|author=Dufresne, F. |year=1922|title=The Snowy Owl-destroyer of game|journal= Bull. Amer. Game Prot. Assoc. |volume=11|pages= 11–12}}</ref> A somewhat varying diet was also reported in [[Prince of Wales Island (Nunavut)|Prince of Wales Island, Nunavut]] where 78.3% of the biomass was lemmings, with 17.8% from [[waterfowl]], 3.3% from [[Stoat|weasel]] and about 1% from other birds.<ref name= Voous/> In [[Fennoscandia]], among 2,700 prey items only a third were [[Norway lemming]]s (''Lemmus lemmus'') and a majority were [[vole]]s at 50.6%, probably largely the [[tundra vole]] (''Microtus oeconomus'').<ref name= Voous/><ref name= Cramp/> A more detailed glance at [[Lapland (Finland)|Finnish Lapland]] showed that amongst 2,062 prey items, 32.5% of the foods were Norway lemmings (though in some years the balance could range up to 58.1%), 28% were [[grey red-backed vole]]s (''Myodes rufocanus'') and 12.6% were tundra voles, with birds constituting a very small amount of the prey balance (1.1%).<ref name= Hakala>{{cite journal|author=Hakala, A., Huhtala, K., Kaikusalo, A., Pulliainen, E., & Sulkava, S. |year=2006|title=Diet of Finnish snowy owls ''Nyctea scandiaca''|journal= Ornis Fennica|volume= 83|issue=2|pages=59}}</ref> In northern Sweden, a more homogenous diet was found with the Norway lemming constituting about 90% of the foods.<ref name= Andersson>{{cite journal|author=Andersson, N. Å. & Persson, B. |year=1971|title=Något om fjällugglans Nyctea scandiaca näringsval i Lappland|journal= Vår Fågelvärld |volume=30|pages= 227–231}}</ref> In the [[Yamal Peninsula]], 40% of the diet was collared lemmings, 34% were [[Siberian brown lemming]] (''Lemmus sibiricus''), 13% were ''[[Microtus]]'' voles and [[Willow ptarmigan|ptarmigan]] and ducks both constituting 8% and with other birds making up much of the remaining balance.<ref>Osmolovskaya, V.N. 1948. ''[Ecology of raptors on the Yamal peninsula]''. – Proc. Inst. Geography, Academy of Sciences of the USSR 61: 4–77 (in Russian).</ref> In some parts of the tundra, snowy owls may opportunistically prey upon [[Arctic ground squirrel]]s (''Spermophilus parryii'').<ref>{{cite journal|doi=10.1644/10-MAMM-A-030.1|title=Habitat selection by arctic ground squirrels (''Spermophilus parryii'')}}</ref> In the [[Hooper Bay]] area (much farther south than they usually nest), various rodents, in highland areas, and [[waterfowl]], in marshland, were taken while breeding.<ref name= Murie/><ref>Brackney, A. W. & King, R. J. (1991). ''Population shifts by Snowy Owls on the Arctic coastal plain of Alaska. Abstract''. In Alaska Bird Conference and Workshop. Anchorage.</ref> When historically breeding on [[Fetlar]] in Shetland, the main prey for snowy owls was [[European rabbit]]s (''Oryctolagus cuniculus''), [[Eurasian oystercatcher]] (''Haematopus ostralegus''), [[parasitic jaeger]]s (''Stercorarius parasiticus'') and [[Eurasian whimbrel]] (''Numenius phaeopus''), in roughly that order, followed by other bird species with most (rabbits and secondary birds) prey taken as adults but for the oystercatchers and jaegers which were taken largely as fully grown but only recently fledged juveniles. 22–26% of oystercatcher and jaeger young in the island were estimated to be taken by snowy owls.<ref name= Tulloch/><ref name= Robinson/> Bird predation by nesting snowy owls is highly opportunistic.<ref name= Holt/> [[Willow ptarmigan|Willow]] (''Lagopus lagopus'') and [[rock ptarmigan]] (''Lagopus muta'') of any age are often fairly regular in the diet of breeding snowy owls but they cannot be said to particularly specialize on these.<ref name= Potapov/><ref>{{cite journal|jstor=40511025|doi=10.14430/arctic2091}}</ref><ref name= Potapova>{{cite journal|author=Potapova, O. |year=2001|title=Snowy owl ''Nyctea scandiaca'' (Aves: Strigiformes) in the Pleistocene of the Ural Mountains with notes on its ecology and distribution in the Northern Palearctic|journal= Deinsea|volume= 8|issue=1|pages= 103–126}}</ref> Evidence was found in the [[Yamal Peninsula]] that the snowy owls became the primary predator of willow ptarmigan and that the predation was so frequent, it may have been the cause of the change of their habitat usage to [[willow]] thickets by the local ptarmigan.<ref>Tarasov, V. V. (2011). ''Summer flocks of the Willow Ptarmigan in the north of the Yamal Peninsula''. In: R. T. Watson, T. J. Cade, M. Fuller, G. Hunt, and E. Potapov (Eds.). ''Gyrfalcons and Ptarmigan in a Changing World''. The Peregrine Fund, Boise, Idaho, USA.</ref> The reliance on ptarmigan has caused some conservation trickle-down concern for the owls because ptarmigan are hunted in large numbers, with the hunters of Norway permitted to cull up to 30% of the regional population.<ref name= Heggoy/> In North America, avian prey on the breeding ground regularly varies from small passerines like [[snow bunting]]s (''Plectrophenax nivalis'') and [[Lapland longspur]]s (''Calcarius lapponicus'') to large waterfowl like [[King eider|king]] (''Somateria spectabilis'') and [[common eider]] (''Somateria mollissima'') and usually the goslings but also occasionally adults of geese such as [[Brant (goose)|brant]]s (''Branta bernicla''), [[snow geese]] (''Anser caerulescens'') and [[cackling geese]] (''Branta hutchinsii'').<ref name= Potapov/><ref name= Holt/><ref name= Manning/><ref>{{cite journal|doi=10.1093/auk/90.2.433}}</ref> Drake eiders of often similar size to the owls themselves are not infrequently the largest prey amongst remains around the nest mound. One nest had the bodies of all eiders that attempting to nest in the vicinity around it.<ref name= Potapov/><ref name= Holt/><ref name= Dorogoy>Dorogoy, I.V . (1987). ''Ecology of small mammal predators in Wrangel Island and their role in the dynamics of lemming numbers''. Vladivostok: DVO AN SSSR. (In Russian).</ref><ref name= Wiggins>{{cite journal|doi=10.2307/4081330|title=Foraging activities of the Snowy Owl (''Nyctea scandiaca'') during a period of low lemming population}}</ref> The threatened and declining [[Steller's eider]] (''Polysticta stelleri'') when nesting in the Utqiaġvik area would appear to avoid the vicinity of snowy owl nests when selecting their own nesting sites due to the predation risk.<ref>{{cite journal|doi=10.14430/arctic493|title=Breeding biology of Steller's eiders (''Polysticta stelleri'') near Barrow, Alaska, 1991–99}}</ref> Intermediately sized [[seabird]]s are often focused on in lieu of available lemmings.<ref name= Holt/> Foods were studied intensively in Iceland. Among 257 prey items found with a total prey mass of {{convert|73.6|kg|lb|abbr=on}}, birds made up 95% of the diet. The leading prey were adult [[rock ptarmigan]], at 29.6% by number and 55.4% by biomass and adult [[European golden plover]] (''Pluvialis apricaria''), at 10.5% by number and 7.2% biomass. The rest of the balance was largely other [[shorebird]]s, which were taken slightly more often as chicks than adults. [[Pink-footed geese]] (''Anser fabalis'') were taken in equal number as goslings and adults, with respectively estimated average weights at these ages of {{convert|800|and|2470|g|lb|abbr=on}}.<ref name= Stenkewitz>Stenkewitz, U., & Nielsen, Ó. K. (2019). ''The Summer Diet of the Snowy Owl (Bubo scandiacus) in Iceland''. Journal of Raptor Research, 53(1), 98–101.</ref> On the isle of [[Agattu]], the diet consisted entirely of birds, as there are no mammals found there.<ref name= Williams>{{cite journal|doi=10.2307/1367296|url=https://sora.unm.edu/sites/default/files/journals/condor/v081n02/p0213-p0214.pdf}}</ref> The much favored food in Agattu was the [[ancient murrelet]] (''Synthliboramphus antiquus''), at 68.4% of the biomass and 46% by number, while the secondary prey were followed numerically by smaller [[Leach's storm-petrel]]s (''Oceanodroma leucorhoa'') (20.8%) and [[Lapland longspur]]s (10%) and in biomass by smallish ducks, the [[green-winged teal]] (''Anas carolinensis'') and [[harlequin duck]] (''Histrionicus histrionicus'') (13.4% biomass collectively).<ref name= Williams/> In the [[Murman Coast]] of Russia, also in the absence of lemmings, [[seabird]]s formed the largest part of the diet.<ref name= Krasnov>Krasnov, Y. (1985). ''To the biology of the Snowy Owl in the Eastern Murman. Birds of Prey and Owls in the Nature Reserves of the Russian Federation''. TSNIL GLAVOKHOTA, 110–116.</ref> ===Winter diet=== [[File:SnowyOwlAmericanBlackDuck.jpg|thumb|right|Snowy owl carries its kill, an [[American black duck]], [[Biddeford Pool, Maine]]]] On the wintering grounds, mammals often predominate in the snowy owl's food inland doing so less in coastal areas. Overall wintering snowy owls eat more diverse foods they do whilst breeding, furthermore coastal wintering snowy owls had more diverse diets than inland ones.<ref name= Holt/> As in summer, moderately sized [[water bird]]s such as [[Eurasian teal|teal]], [[northern pintail]] (''Anas acuta'') and numerous [[alcid]]s and the like are often focused on when hunting birds.<ref>{{cite journal|author1=Stronach, P. |author2= Cooper, J. |year=2010|title=Snowy Owl pellet containing Eurasian Teal|journal= British Birds|volume= 103|issue=6|pages= 360–361}}</ref><ref>{{cite journal|author=1Valenziano, R. L.|author2= Labedz, T. E. |year=2014|title=Stomach Content Analysis of Recent Snowy Owl (''Bubo scandiacus'') Specimens from Nebraska|url=https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=2354&context=nebbirdrev|journal= Neb. Bird Review|volume= 80 |issue=3|pages= 122–127}}</ref><ref>{{cite journal|title=Forensic techniques identify the first record of Snowy Owl (''Bubo scandiacus'') feeding on a Razorbill (''Alca torda'')|doi=10.1676/14-176.1}}</ref><ref>{{cite journal|doi=10.1111/jav.01257}}</ref> The diet in 62 pellets, amongst at least 75 prey items, from coastal [[Oregon]] showed the main foods as [[black rat]] (''Rattus rattus'') (at an estimated 40%), [[red phalarope]] (''Phalaropus fulicarius'') (31%) and [[bufflehead]] (''Bucephala albeola'') (19%). Witnessed attacks were mostly upon buffleheads in Oregon.<ref name= Patterson>Patterson, J. M. (2007). ''An analysis of Snowy Owl (Bubo scandiacus) diet during the 2005 to 2006 irruption along the Oregon and Washington coasts''. Northwestern Naturalist, 88(1), 12–15.</ref> In coastal southwestern [[British Columbia]], the diet among 139 prey items was 100% avian. The predominant prey were [[water bird]]s, mostly snatched directly from surface of the water and largely weighing {{convert|400|to|800|g|lb|abbr=on}}, i.e. buffleheads (at 24% by number and 17.4% by biomass of foods) and [[horned grebe]]s (''Podiceps auritus'') (at 34.9% by number and 24.6% by biomass), followed by variously other water birds, often the slightly larger species of [[glaucous-winged gull]] (''Larus glaucescens'') and the [[American wigeon]] (''Mareca americana'').<ref>{{cite journal|doi=10.2307/3800714}}</ref> A different study of this area also showed the predominance of ducks and other water birds to wintering snowy owls here, although [[Townsend's vole]] (''Microtus townsendii'' ) (10.65%) and [[snowshoe hare]] (''Lepus americanus'') (5.7%) were also notably in a sample of 122 prey items.<ref name= Campbell>{{cite journal|author1=Campbell, R. W. |author2= Preston, M. I. |year=2009|title=Featured Species - Snowy Owl (''Bubo scandiacus'')|journal=Widllife Afield|volume= 6 |issue=2|pages= 173–255}}</ref> During winter, snowy owls consume more strongly nocturnal prey than lemmings such as ''[[Peromyscus]]'' mice and [[northern pocket gopher]]s (''Thomomys talpoides'').<ref name= Holt/><ref>{{cite journal|doi=10.29173/bluejay5360}}</ref> In southern Alberta, 248 prey items were found with [[North American deermouse]] (''Peromyscus maniculatus''), at 54.8% by number, and [[meadow vole]]s (''Microtus pennsylvanica''), at 27% by number, as the main foods of snowy owls over two years. Other prey in Alberta were [[grey partridge]] (''Perdix perdix'') (at 5.79% of total), [[White-tailed jackrabbit|jackrabbit]]s, [[weasel]]s and [[Short-eared owl|owls]]. [[Richardson's ground squirrel]]s (''Urocitellus richardsonii'') were consumed heavily in the Alberta study in a brief converged times of hibernation emergence and overwintering snowy owls.<ref name= Boxall2/> The sexual dimorphism in prey selection was also studied here, with male owls mainly focusing exclusively on the small rodents, females also took the same rodents but supplemented the diet with all alternate and larger prey.<ref name= Boxall2/> Overall, the meadow and [[montane vole]]s (''Microtus montanus'') constituted 99% of over 4500 prey items in Montana.<ref name= Detienne/> In [[Horicon Marsh]] in winter, 78% of the diet was meadow vole, with 14% being [[muskrat]]s (''Ondatra zibethicus''), 6% ducks and smaller balances of rats and other birds.<ref>{{cite journal|author=Keith, L. B. |year=1963|title=A note on Snowy Owl food habits|journal=The Wilson Bulletin|volume= 75|issue=3|pages= 276–277}}</ref> Snowy owls found in Michigan took meadow voles for 86% of the diet, [[white-footed mouse]] (''Peromyscus leucopus'') for 10.3% and [[northern short-tailed shrew]] (''Blarina brevicauda'') for 3.2%.<ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v092n01/p0116-p0120.pdf|author=Chamberlin, M. L. |year=1980|title=Winter hunting behavior of a snowy owl in Michigan|journal= The Wilson Bulletin|pages= 116–120|volume=92|issue=1}}</ref> Of 127 stomachs in New England in four irruptive winters from 1927 to 1942, of 155 prey items, 24.5% were [[brown rat]]s, 11.6% were meadow voles and 10.3% were [[dovekie]] (''Alle alle''), with a smaller balance of [[snowshoe hare]] and birds from snow buntings to [[American black duck]]s (''Anas rubripes''). During the same years, stomach contents in Ontario included 40 identified prey items, led by brown rats (20%), white-footed mice (17.5%) and meadow voles (15%); of 81 prey items from [[Pennsylvania]] in 60 stomachs that were not empty, [[eastern cottontail]] (''Sylvilagus floridanus'') (32%), meadow vole (11.1%), [[Chicken|domestic chicken]] (''Gallus gallus domesticus'') (11.1%) and [[northern bobwhite]] (''Colinus virginianus'') (5%) were the most often identified prey species.<ref name= Gross>{{cite journal|doi=10.2307/4079593|url=https://sora.unm.edu/sites/default/files/journals/auk/v061n01/p0001-p0018.pdf}}</ref> Introduced [[common pheasant]]s were found to be somewhat more vulnerable than native American gamebirds like [[ruffed grouse]] due to their tendency to crouch rather than flush when approached by a flighted predator like the snowy owl in a [[Glade (ecology)|glade]] or field.<ref name= Gross/> Some snowy owls wintering on [[Cliffed coast|rocky coasts]] and [[Jetty|jetties]] were known in New England to live almost entirely off of [[purple sandpiper]]s (''Calidris maritima'').<ref name= Gross/> The availability of brown rats may draw snowy owls to seemingly unattractive settings such as [[Landfill|garbage dump]]s and under bridges. Meanwhile, snowy owls wintering in [[Lowell, Massachusetts]] were seen to live largely off of [[rock dove]]s (''Columba livia'') caught off of buildings.<ref name= Gross/> Of 87 prey from stomachs in Maine, 35% were [[Rattus|rats]] or mice, 20% were snowshoe hares and 10% were passerines.<ref>{{cite journal|doi=10.2307/3795698}}</ref> A small study of 20 prey items in an irruptive winter in Kansas found that 35% of the prey were [[red-winged blackbird]] (''Agelaius phoeniceus''), 15% [[prairie vole]]s (''Microtus ochrogaster'') and 10% each by [[American coot]] (''Fulica americana'') and [[hispid cotton rat]]s (''Sigmodon hispidus'').<ref name= Young>{{cite journal|author=Young, E.A., Blake, C., Graham, R., Otte, C., Beckman, M. & Klem, D. |year=2014|title=Prey items from Snowy Owl (''Bubo scandiacus'') Pellets during the 2011–2012 Irruption in Kansas|journal=Kansas Ornithological Society|volume= 65 |issue=4|pages=33–40}}</ref> On the isle of [[St. Kilda, Scotland|St. Kilda]], 24 pellets were found for non-breeding snowy owls that stayed through the early summer. Of 46 prey items, the [[St Kilda field mouse]] (''Apodemus sylvaticus hirtensis'') was predominant by number at 69.6% but constituted 16.8% of biomass while adult [[Atlantic puffin]] (''Fratercula arctica'') constituted 63.5% of the prey biomass and 26% by number (rest of the balance being juvenile puffins and [[great skua]]s (''Stercorarius skua'')).<ref name= Miles>Miles, W. T. S., & Money, S. (2008). ''Behaviour and diet of non-breeding Snowy Owls on St Kilda''. Scottish Birds, 28, 11.</ref> The main subspecies of [[wood mouse]] was similarly dominant in the diet within [[County Mayo]], Ireland and were presumably snatched at night due to their strict [[nocturnality]].<ref>{{cite journal|author1=Murrey, T. |author2= Sleeman, D. |year=2005|title=Dietary analysis from the Snowy Owls pellets ''Nyctea scandiaca'' Linnaeus 1958, from the Mullet Peninsula, Co, Mayo|journal= Irish Naturalists' Journal|volume= 283|pages= 136}}</ref> In [[Knockando, Moray|Knockando]], the winter diet was led by [[European rabbit]]s (40.1%), [[red grouse]] (''Lagopus lagopus scotica'') (26.4%) and adult [[mountain hare]] (''Lepus timidus'') (20.9%) (in 156 pellets); in [[Ben Macdui]], the diet was led by rock ptarmigan (72.3%), [[field vole]]s (''Microtus agrestis'') and juvenile mountain hare (8.5%) (33 pellets); in [[Cabrach]], the diet was led by red grouse (40%), mountain hare (20%) and European rabbit (15%) (16 pellets).<ref name= Savory>{{cite journal|url=https://www.researchgate.net/publication/336837560_Unpublished_information_in_the_SOC_Archive_on_Snowy_Owl_diet_at_three_locations_in_Moray_in_the_1960s_Unpublished_information_in_the_SOC_Archive_on_Snowy_Owl_diet_at_three_locations_in_Moray_in_the_19|author=Savory, J. |year=2019|title=Unpublished information in the SOC Archive on Snowy Owl diet at three locations in Moray in the 1960s|journal= Scottish Birds|volume= 202|issue=204|pages= 202}}</ref> Among 110 prey items found for snowy owls found wintering during irruption in southern Finland, all but 1 prey item were field voles (the only other prey being a single [[long-tailed duck]] (''Clangula hyemalis'')).<ref name= Hakala/> Far to the east, wintering owls in the [[Irkutsky District]] were found to subsist mostly on [[narrow-headed vole]]s (''Microtus gregalis'').<ref name= Maleev>Maleev, V.G. & Popov, V. V. (2007). ''Birds of forest-steppes of the Upper Angara river basin''. Irkutsk.</ref> In a wintering population in Kurgaldga Nature Reserve of Kazakhstan, the main foods were [[grey red-backed vole]]s at 47.4%, [[winter white dwarf hamster]] (''Phodopus sungorus'') at 18.4%, [[steppe pika]] (''Ochotona pusilla'') at 7.9%, muskrat at 7.9%, [[Eurasian skylark]] (''Alauda arvensis'') at 7.9%, [[grey partridge]] at 5.3%, and both [[steppe polecat]] (''Mustela eversmanii'') and [[yellowhammer]] (''Emberiza citrinella'') at 2.6%<ref>Mosalev, A. (1969). ''About wintering of Snowy Owl in the Kurgaldga Nature Reserve''.</ref> On the [[Kuril Islands]], wintering snowy owls main foods were reported as tundra voles, brown rats, ermines and whimbrel, in roughly that order.<ref name= Potapov/> Data from the [[Logan Airport]] in over 6,000 pellets shows that meadow vole and brown rat predominated the diet in the area, supplanted by assorted birds both small and large.<ref name= Holt/> [[American black duck]]s were primarily taken among bird species with other birds taken here including relatively large and diverse species [[Canada geese]] (''Branta canadensis''), brants, [[American herring gull]]s (''Larus argentatus''), [[double-crested cormorant]] (''Phalacrocorax auritus''), [[great blue heron]] (''Ardea herodias''), in addition to some formidable mammals such as [[Cat|house cat]], [[American mink]] (''Mustela vision''), and [[striped skunk]] (''Mephitis mephitis'').<ref name= Holt/> Given the large size of some of this prey, it can be projected that the snowy owl can kill adult prey of around twice their own weight (i.e. geese, cats, skunks, etc.).<ref name= Holt/> Other large prey is sometimes taken by snowy owls, all roughly within the {{convert|2|to|5|kg|lb|abbr=on}} weight range often include adults of large [[leporid]]s such as [[Arctic hare]] (''Lepus arcticus''),<ref name= Holt/> [[Alaskan hare]] (''Lepus othus''),<ref>Best, T. L., & Henry, T. H. (1994). ''Lepus othus''. Mammalian Species, (458), 1–5.</ref> [[mountain hare]]<ref>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V54/V54_N08/V54_N08_P307_320_A051.pdf|author=Bergman, G. |year=1961|title=The food of birds of prey and owls in Fenno-Scandia|journal= British Birds|volume= 54|issue=8|pages= 307–320}}</ref> and [[white-tailed jackrabbit]]s (''Lepus townsendii'').<ref name= Boxall2/> As well as several species of geese, probable cygnets of [[Tundra swan|Bewick's swan]]s (''Cygnus columbianus bewickii'')<ref>Nagy, S., Petkov, N., Rees, E., Solokha, A., Hilton, G., Beekman, J., & Nolet, B. (2012). [https://www.unep-aewa.org/en/publication/international-single-species-action-plan-conservation-northwest-european-population International single species action plan for the conservation of the northwest European population of Bewick's Swan (''Cygnus columbianus bewickii'')]. Wetlands International and The Wildfowl & Wetlands Trust (WWT), AEWA Technical Series, (44).</ref> as well as adults of the following: [[western capercaillie]] (''Tetrao urogallus'') (of both sexes),<ref>Gilyazov, A. V. (2005). ''Snowy Owl Nyctea scandiaca Linnaeus, 1758''. Red-data Book of the Murmansk Region. Murmansk: Murmansk book publishers: 316—318. [in Russian].</ref> [[greater sage-grouse]] (''Centrocercus urophasianus'')<ref>{{cite journal|doi=10.1002/jwmg.21168}}</ref> and [[yellow-billed loon]]s (''Gavia adamsii'').<ref>Uher-Koch, B. D., M. R. North, and J. A. Schmutz (2020). Yellow-billed Loon (''Gavia adamsii''), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.</ref> At the other end of the scale, the snowy owl has been known to take birds down to size of {{convert|19.5|g|oz|abbr=on}} [[dark-eyed junco]]s (''Junco hyemalis'') and mammals down the size of {{convert|8.1|g|oz|abbr=on}} [[common shrew]]s (''Sorex araneus'').<ref name= Hakala/><ref name= Young/><ref name= CRC1>Dunning, Jr., J. B. (1993). ''CRC handbook of avian body masses''. CRC Press, Boca Raton, FL.</ref> Fish are rarely taken anywhere but the snowy owl has been known to prey upon [[Arctic char]] (''Salvelinus alpinus'') and [[lake trout]] (''Salvelinus namaycush'').<ref name= Voous/><ref name= Gross/><ref name= Bailey>Bailey, A. M. (1948). ''Birds of Arctic Alaska''. Colorado Mus. Nat. Hist., Popular Ser., 8.</ref> ===Interspecific predatory relationships=== [[File:Snowy owl and peregrine falcon.webm|thumb|left|A waterlogged snowy owl in winter victim to the very swift [[Mobbing (animal behavior)|mobbing]] of a [[peregrine falcon]].]] The snowy owl is in many ways a very unique owl and differs from other species of owl in its [[ecological niche]].<ref name= Voous/><ref name= Johnsgard/> Only one other owl, the [[short-eared owl]], is known to breed in the High Arctic.<ref name= Voous/> However, the snowy owl shares its primary prey, the [[True lemming|brown]] and [[collared lemming]]s, with a number of other avian predators. In sometimes differing parts of the Arctic, competing predators for lemmings are, in addition to short-eared owls, [[pomarine jaeger]]s (''Stercorarius pomarinus''), [[long-tailed jaeger]]s (''Stercorarius longicaudus''), [[rough-legged buzzard]]s (''Buteo lagopus''), [[hen harrier]]s (''Circus cyaenus''), [[northern harrier]]s (''Circus hudsonius'') and generally less specialized [[gyrfalcon]]s (''Falco rusticollis''), [[peregrine falcon]]s (''Falco peregrinus''), [[glaucous gull]]s (''Larus hypoboreus'') and [[common raven]]s (''Corvus corax''). Certain carnivorous mammals, especially the [[Arctic fox]] and, in this region, the [[Stoat|ermine]], are also specialized to hunt lemmings.<ref name= Voous/><ref name= Pitelka/><ref>{{cite journal|doi=10.2307/3545963}}</ref><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v082n02/p0130-p0157.pdf|author=Maher, W. J. |year=1970|title=The Pomarine Jaeger as a Brown Lemming predator in northern Alaska|journal= Wilson Bulletin|volume= 82|pages= 130–157}}</ref> Most of the lemming predators are intolerant of the competition given the scattered nature of lemming populations and will displace and/or kill one another given the chance. However, given the need to conserve energy in the extreme environment, the predators may react passively to one another.<ref>{{cite journal|jstor=4314894|author=Wiklund, C. G., Angerbjörn, A., Isakson, E., Kjellén, N., & Tannerfeldt, M. |year=1999|title=Lemming predators on the Siberian tundra|journal=Ambio|volume= 281–286}}</ref><ref name="Gilg" /> When unusually breeding south in the Subarctic such as western Alaska, Scandinavia and central Russia, the number of predators with which the snowy owls are obligated to share prey and compete with may be too numerous to name.<ref name= Potapov/> The taking of the young and eggs of snowy owls has been committed by a large number of predators: [[Buteo|hawks]] and [[eagle]]s, the northern [[Skua|jaeger]]s, peregrine and gyrfalcons, glaucous gulls, common ravens, [[Arctic wolf|Arctic wolves]] (''Canis lupus arctos''), [[polar bear]]s, [[brown bear]]s (''Ursus arctos''), [[wolverine]]s (''Gulo gulo'') and perhaps especially the Arctic fox.<ref name= Holt/><ref name= Taylor/><ref>Ovsyanikov, N.G. & Menushina, I.E. (1986). ''[Competition for food between the Snowy Owl (Nyctea scandiaca) and the arctic fox (Alopex lagopus)]''. Zoologischeskii Zhurnal. 65(6): 901–910. In Russian with English summary.</ref> Adult snowy owls on the breeding grounds are far less vulnerable and can be justifiably qualified as an [[apex predator]].<ref name= Konig/><ref name= Voous/> Instances of killing of adult snowy owls on the breeding grounds have been witnessed to be committed by a pair of [[pomarine jaeger]]s on an incubating adult female snowy owl (possibly merely a competitive attack as she was left uneaten) and by an Arctic fox that killed an adult male snowy owl.<ref name= Bailey/><ref>Menyushina, I. E. (1994). "Interspecies relation of the polar fox (''Alopex lagopus'' L.) and the Snowy Owl (''Nyctea scandiaca'' L.) during the breeding season in the Wrangel Island. 1". Lutreola 3: 15–21.</ref> [[File:Die Raubvögel Deutschlands und des angrenzenden Mitteleuropas (Pl. L) (21138120888).jpg|thumb|An early illustration showing snowy owl predation upon a [[gyrfalcon]].]] When it goes south to winter outside of the Arctic, the snowy owl has a potential to interact with a number of additional predators.<ref name= Voous/> By necessity, it shares its wintertime diverse prey with a number of formidable predators.<ref name= Voous/><ref name= Holt/> These are known to include their cousins, the [[great horned owl]] and the [[Eurasian eagle-owl]]. They are relieved of heavy competition from the related species by differing temporal activity, i.e. being more likely to actively hunt in daytime, and by habitat, using rather more open (quite often nearly treeless) habitats than them.<ref name= Potapov/><ref name= Voous/> During a study of wintering snowy owls in [[Saskatchewan]], the authors indicated that the snowy owls may avoid areas inhabited and defended by great horned owls. Although they usually occurred here outside of a {{convert|800|m|ft|abbr=on}} radius of central great horned owl ranges, they did not avoid the {{convert|1600|m|ft|abbr=on}} radius and different habitat usage may be a dictating factor.<ref name= Chang2>Chang, A. M. (2017). ''Habitat use, movement patterns, and body condition of male and female Snowy Owls (Bubo scandiacus) in winter'' (Doctoral dissertation, University of Saskatchewan).</ref> Given their mildly slighter size, it is unlikely that great horned owls (unlike the larger eagle-owl) would regularly dominate snowy owls in interactions and either species may give way to other depending on the size and disposition of the owls involved.<ref name= Potapov/><ref name= Voous/> Little study has been undertaken into the [[Trophic level|trophic competition]] of snowy owls with other predators during winter and, due to their scarcity, few predators are likely to expel much energy on competitive interactions with them, although many other predators will engage in anti-predator [[Mobbing (animal behavior)|mobbing]] of snowy owls.<ref name= Voous/><ref name= Holt/> Largely in winter, snowy owls have been the victim of a number of larger avian predators, though attacks are likely to be singular and rare.<ref name= Voous/><ref name= Holt/> Instances of predation on snowy owls are known to have been committed several times in winter only by [[Eurasian eagle-owl]]s.<ref name= Mikkola3>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V69/V69_N04/V69_N04_P144_154_A030.pdf|author=Mikkola, H. |year=1976|title=Owls killing and killed by other owls and raptors in Europe|journal= British Birds|volume= 69|pages= 144–154}}</ref> Additionally, [[golden eagle]]s (''Aquila chrysaetos'') have been known to prey on snowy owls as well as all northern [[sea eagle]]s: the [[Bald eagle|bald]] (''Haliaeetus leucocephalus''), [[White-tailed eagle|white-tailed]] (''Haliaeetus albicilla'') and [[Steller's sea eagle]]s (''Haliaeetus pelagicus'').<ref name= Holt/><ref name= Campbell/><ref>{{cite journal|author=Johnson, M.J. |year=1995|title=Bald Eagle predation on Snowy Owl|journal= Loon|volume= 67|issue=2|pages=107}}</ref> Snowy owls are also sometimes killed by birds that are mobbing them. In one instance, a [[peregrine falcon]] killed a snowy owl in a stoop after the owl had itself killed a fledgling falcon.<ref name= Bent/><ref name= Bailey/><ref>Nelson, E. W. (1887). ''Birds of Alaska'', p. 35-222. In H. W. Henshaw [ed.], Report upon natural history collections made in Alaska between the years 1877 and 188 1. No. III Arctic Series, Signal Service, U.S. Army, Government Printing Office,-Washington, DC.</ref> Anecdotal report indicate predation by [[gyrfalcon]]s (on snowy owls of unknown age and condition) but it was possibly also an act of mobbing.<ref name= Heggoy>Heggøy, O., & Øien, I. J. (2014). [https://www.birdlife.no/innhold/bilder/2014/01/29/2586/nof_rapport_12014.pdf ''Conservation status of birds of prey and owls in Norway'']. NOF/BirdLife Norway-Report, 1, 1–129.</ref> In another, a huge [[Flock (birds)|throng]] of [[Arctic tern]]s (''Sterna paradisaea'') relentlessly swarmed and attacked a snowy owl until it meet its demise.<ref>Meinertzhagen, R. (1959). ''Pirates and Predators: The piratical and predatory habits of birds''. Oliver & Boyd.</ref> Almost certainly more often than being victim of other predators, snowy owls are known to dominate, kill and feed on a large diversity of other predators.<ref name= Voous/><ref name= Mikkola3/> Snowy owls, much like other ''Bubo'' owls, will opportunistically kill other birds of prey and predators. Although they will readily plunder the nests of other raptorial birds given the opportunity, most predations are on full-grown raptorial birds during winter due to the scarcity of raptor nests in the open tundra.<ref name= Voous/> In addition, most competing predators of the Arctic, excepting the very large mammals, are probably vulnerable to a hungry snowy owl.<ref name= Voous/><ref name= Holt/> In data from the [[Logan Airport]] alone over different winters, the snowy owls were observed to have preyed upon an impressive diversity of other raptorial birds: [[rough-legged buzzard]]s, [[American kestrel]]s (''Falco sparverius''), [[peregrine falcon]]s, [[barn owl]]s, other snowy owls, [[barred owl]]s (''Strix varia''), [[northern saw-whet owl]]s (''Aegolius acadicus'') and [[short-eared owl]]s. While owls are likely encountered during corresponding hunting times, it is likely that the swift falcons are usually ambushed at night (much as other ''Bubo'' owls will do).<ref name= Holt/> In both the tundra and the wintering ground, there are several accounts of predation by snowy owls on short-eared owls.<ref name= Potapov/><ref name= Mikkola3/><ref>{{cite journal|doi=10.2307/1368028}}</ref> In addition, snowy owls have been known to prey on [[northern harrier]]s,<ref name= Holt/> [[northern goshawk]]s (''Accipiter gentilis'')<ref name= Voous/> and [[gyrfalcon]]s.<ref name= Voous/><ref name= Mikkola3/> In a few cases, both juvenile and adult [[Arctic fox]]es have been known to fall prey to snowy owls.<ref name= Parker/><ref name= Stenkewitz/><ref name= Krechmar/><ref name="Gilg">{{cite journal|doi=10.1111/j.2006.0030-1299.14125.x}}</ref><ref>{{cite journal|title=''Alopex lagopus''|doi=10.1644/0.713.1}}</ref> A wintering snowy owl in [[Saskatchewan]] was observed to have preyed on an adult [[red fox]] (''Vulpes vulpes''). Predation by snowy owls on red foxes was also reported in the [[Irkutsky District]] of Russia. With an adult weight around {{convert|6|kg|lb|abbr=on}} (and far from defenseless), red fox may be the largest known prey known for snowy owls.<ref name= Maleev/><ref>{{cite journal|doi=10.29173/bluejay3979}}</ref> Besides aforementioned predation on domestic cats and skunks, several members of the [[weasel]] family, both small and relatively large, are known to be opportunistically hunted by snowy owls.<ref name= Potapov/><ref name= Voous/><ref name= Holt/><ref name= Hakala/><ref>{{cite journal|doi=10.2307/3565424}}</ref> As a result of its potential predator status, the snowy owl is frequently mobbed at all times of the year by other predatory birds, including fierce dive-bombing by several of the northern falcons on the wintering grounds, including even by the relatively tiny but fierce and very agile [[Merlin (bird)|merlin]] (''Falco columbarius''). The much bulkier snowy owls cannot match the speed and flight ability of a falcon, ai may be almost relentlessly tormented by some birds such as peregrines.<ref name= Voous/><ref name= Mikkola3/><ref>{{cite journal|doi=10.29173/bluejay208}}</ref> ==Breeding== ===Pair bond and breeding territory=== In Utqiaġvik, of 239 recorded breeding attempts, 232 were monogamous, the other 7 [[Bigamy|social bigamy]].<ref name= Holt/> On [[Baffin Island]], 1 male bred with 2 females and sired 11 total fledged young.<ref name= Watson/> Another case of bigamy was reported in Norway where the 2 females bred to one male were {{convert|1.3|km|mi|abbr=on}} apart in nest site location.<ref name= Hagen/> On Feltar from 1967 to 1975, a male breed with two females, 1 younger and was possibly his own [[Incest|daughter]]. In the Feltar males first time breeding with both females, he did not bring food to the younger female. However, when older female disappeared the following year, the male and younger female producing 4 young, but disappeared the subsequent year altogether in 1975.<ref name= Robinson/> There are also unconfirmed cases of [[polyandry]], with 1 female being fed by 2 males. Snowy owls can breed once per year but when food is scarce many do not even attempt to breed.<ref name= Konig/><ref name= Voous/> Despite frequent wandering in search of food, they generally adhere more so than to a strict breeding season than [[short-eared owl]]s nesting in the tundra.<ref name= Voous/> 9 radio-tagged female snowy owls about [[Bylot Island]] were tracked to study how pre-laying snow cover effects their searching behavior for breeding area. These tracked females searched an average of 36 days and covered an average of {{convert|1251|km|mi|abbr=on}}. It is thought that the male and female mutually find an attractive breeding spot independently and converge.<ref>{{cite journal|doi=10.1186/s40462-015-0028-7}}</ref> The breeding territory normally averages about {{convert|2.6|km2|sqmi|abbr=on}} as in both [[Baffin Island]] and [[Ellesmere Island]] but varies in accordance to abundance of food and density of owls.<ref name= Konig/><ref name= Watson/> Nesting territories average at Baffin island in the range of {{convert|8|to|10|km2|sqmi|abbr=on}} during poor lemming years.<ref name= Watson/> Nesting territories may up to {{convert|22|km2|sqmi|abbr=on}} on [[Southampton Island]] and had a mean distance of {{convert|4.5|km|mi|abbr=on}} between active nests.<ref name= Sutton1/> In Utqiaġvik, nesting pairs can vary from none to at least 7 and the territories average {{convert|5|to|10|km2|sqmi|abbr=on}}, with mean nest distances of {{convert|1.5|to|6|km|mi|abbr=on}}.<ref name= Pitelka/> In the Norwegian highlands, nesting occurs only at times of plenty distances of {{convert|1.2|to|3.7|km|mi|abbr=on}} between nests, averaging {{convert|2.1|km|mi|abbr=on}}.<ref name= Hagen/> Males marks territory with singing and display flights and likely always initiates.<ref name= Watson/> During the display, he engages in exaggerated wing beats with a shallow undulating and bouncy courtship flight with wings held in a [[Dihedral (aeronautics)|dihedral]]. He often drops to the ground but then flies again to only glide gently back down. Overall, the flight is somewhat reminiscent of the flight of a [[moth]].<ref name= Watson/><ref name= Pitelka/><ref name= Tulloch/><ref name= Robinson/> Females will answer her mate with her song during courtship.<ref name= Konig/> While courting, the male often also carries a lemming in his bill, then bows with cocked tail, similarly as in related owls (seldom displaying some other prey like [[snow bunting]]s). He then flaps his wings open in an emphatic manner, with the ground display being relatively brief (about 5 minutes). The female may possibly refuse to breed if ritual not performed.<ref name= Watson/><ref name= Taylor/> A possible courtship was engaged in by a male in southern Saskatchewan when a female was sighted.<ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v094n01/p0079-p0081.pdf|author1=Boxall, P. C. |author2= Lein, M. R. |year=1982|title=Possible courtship behavior of Snowy Owls in winter|journal= Wilson Bulletin|volume= 94|pages=79–81}}</ref> On Southampton Island, at least 20 males observed in late May in a "lemming year".<ref name= Voous/><ref name= Sutton1/> Nesting territory defense displays, not highly different from courtship displays, includes undulating flight and stiffly raised wings with bouts of exaggerated, delayed wing beats, looking like enormous white moths exposing their white wings under the sun.<ref name= Taylor/> At times, competing males will interlock claws in mid-air.<ref name= Voous/> Territorial and nuptial displays are followed by a ground display by the male with the wings arched up in an "angel" posture, visible for well over a mile.<ref name= Voous/> ===Nest sites=== [[File:Tundra Polygons and Pingos (9514080830).jpg|thumb|left|Snowy owls often seek out polygons such as these in the [[tundra]].]] Most individuals arrive at the nest site by April or May with a few overwintering arctic exceptions.<ref name= Murie/><ref name= Marine/><ref name= Pitelka2/> Males advertises potential nest sites to his mate by scratching the ground and spreading his wings over it.<ref name= Konig/> The nest is usually a shallow depression on a windswept eminence in the open tundra. There seems to be a variety of qualifiers for appropriate nest sites. The nest site is typically snow-free and dry relative to the surrounding environment, usually with a good view of the surrounding landscape. The nest may be made of [[ridge]]s, [[Mound|elevated mound]]s, high [[polygon]]s, [[hummock]]s, hills, man-made mounds and occasionally [[Outcrop|rocky outcrops]]. If covered with vegetation, taller plants that may obstruct view are plucked away sometimes.<ref name= Konig/><ref name= Voous/><ref name= Watson/><ref name= Pitelka2/><ref name= Holt3>{{cite journal|doi=10.5253/078.097.0422}}</ref> The nest sites are often long-established and naturally created by the freeze-thaw process of the tundra.<ref name= Voous/><ref name= Holt/> [[Bar (river morphology)|Gravel bars]] may be used as well.<ref name= Potapov/> The female may take the most active role in the nest's condition of any owl species.<ref name= Holt/><ref name= Mikkola/> No owl build their own nests but female snowy owls take about three days constructing a scrape, digging with her claws and rotating until a fairly circular bowl is formed. She will still not construct or add foreign materials to the nest (despite some circumstantial evidence of moss and grass from outside the nest mound being found).<ref name= Holt/><ref name= Murie/><ref name= Tulloch/> In two separate cases in Utqiaġvik, two separate females dug out a second scrape to the side and below the main nests and appeared to have called all chicks to the more secluded nest to ride out severe weather until the skies cleared.<ref name= Holt/> The Utqiaġvik nest scrapes averaged {{convert|47.7|x|44|cm|in|abbr=on}} in 91 with a mean depth of {{convert|9.8|cm|in|abbr=on}} while the scrapes were smaller in [[Hooper Bay]], reportedly {{convert|25|to|33|cm|in|abbr=on}} diameter and {{convert|4|to|9|cm|in|abbr=on}} in depth.<ref name= Murie/><ref name= Holt3/> Occasionally, in the lower tundra, snowy owls may too use old nests of [[rough-legged buzzard]]s as well as abandoned [[eagle]] nests.<ref name= Voous/> Unlike other northerly breeding raptorial birds, the snowy owl is not known to nest on cliffs and the like, so do not enter into direct competition with eagles, falcons, ravens or other ''Bubo'' owls when nesting to the relative south.<ref name= Voous/> The area of nest mound often has a relatively rich plant life which attract the lemmings, which may tunnel right under and around the owl's nest.<ref name= Voous/> [[Goose|Geese]], ducks and [[shorebird]]s of several species known to gain incidental protection by nesting close to snowy owls. Conversely, the snowy owls will sometimes kill and eat both young and adults of these birds, which implies a trade-off in the benefits.<ref name= Parmelee/><ref name= Murie/><ref name= Robinson/><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v109n03/p0449-p0461.pdf|author=Tremblay, J. P., Gauthier, G., Lepage, D., & Desrochers, A. |year=1997|title=Factors affecting nesting success in greater snow geese: Effects of habitat and association with snowy owls|journal= The Wilson Bulletin|pages= 449–461|volume=109|issue=3|jstor=4163840}}</ref><ref>{{cite journal|doi=10.1139/z96-210}}</ref><ref>{{cite journal|doi=10.1007/BF02465456|title=How do Brent Geese (''Branta b. bernicla'') cope with evil}}</ref><ref>Smith, P. A. (2003). ''Factors affecting nest site selection and reproductive success of tundra nesting shorebirds'' (Doctoral dissertation, University of British Columbia).</ref> ===Eggs=== [[File:Eggs of British Birds Seebohm 1896 Plate6.jpg|thumb|An illustration of 8 European owl species' eggs, with the snowy owl in the middle of the right row. Note the much larger egg of the [[Eurasian eagle-owl]] at bottom.]] Egg-laying normally begins during early May to the first 10 days of June.<ref name= Konig/> Late thaws are harmful to them since they allow too little time for the full breeding process, with particularly importance given to good food supply in May for adults, even more so apparently than food supply in July when young are being fed.<ref name= Hume/> Late nests are possible cases of inexperienced pairs, low food supplies, bigamy or even replacement clutches.<ref name= Holt/><ref name= Watson/><ref name= Robinson/> The clutch is extremely variable in size averaging around 7–9, with up to 15 or 16 eggs recorded in extreme cases. The clutch size very large relative to related species.<ref name= Konig/><ref name= Voous/> Mean clutch sizes were 7.5 in a sample of 24 in Hooper Bay (range of 5–11); 6.7 in a sample of seven from Utqiaġvik (4–9); 9 in a sample of a sample of 5 in Baffin Island; 9.8 on Victoria Island; 8.4 (in a sample of 14) on Elsemere Island; 7.4 on Wrangel Island and 7.74 in Finnish Lapland.<ref name= Pitelka/><ref name= Watson/><ref name= Cramp/><ref name= Sutton/><ref name= Hart/> The average clutch size was 9.8 in a good year in [[Victoria Island (Canada)|Victoria Island]] while in a good year in Utqiaġvik the mean was 6.5.<ref name= Parmelee/><ref name= Pitelka/> The clutch is laid directly to the ground and are pure, glossy white.<ref name= Konig/><ref name= Holt/> An average egg is around {{convert|56.4|x|44.7|mm|in|abbr=on}} with a range of heights from {{convert|50|to|70.2|mm|in|abbr=on}} and diameter of {{convert|41|to|49.3|mm|in|abbr=on}}. Egg weights are around {{convert|47.5|to|68|g|oz|abbr=on}}, the median or average being {{convert|53|and|60.3|g|oz|abbr=on}} in different datasets.<ref name= Konig/><ref name= Watson/><ref name= Hagen/><ref>Baicich, P.J. & Harrison, C.J.O. (1997). ''A Guide to the Nests, Eggs, and Nestlings of North American Birds''. Academic Press, San Diego, California.</ref><ref>Schönwetter, M. (1960). ''Handbuch der Oologie'' (Ed. W. ME~SE). Vol. 1. Berlin.</ref> The average egg size is relatively small, about 20% smaller than Eurasian eagle-owl eggs and 8% smaller than great horned owl eggs.<ref name= Potapov/><ref name= Voous/><ref>Bendire, C. E. (1892). ''Life histories of North American birds with special reference to their breeding habits and eggs''. U.S. National Museum Special Bulletin 1.</ref> Laying intervals are normally 2 days (41–50 hours mostly).<ref name= Konig/><ref name= Schaanning>Schaanning, H. T. L. (1907). ''Østfinmarkens fuglefauna''. Bergens Mus. Arb. 8:1–98.</ref><ref>Pleske, T. (1928). ''Birds of the Eurasian tundra''. Mem. Boston Soc. Nat. Hist. 6:111–485.</ref> The laying intervals can range up to 3–5 days in inclement weather.<ref name= Voous/><ref>Parmelee, D. F., Stephens, H. A. & Schmidt, R. H. (1967). ''The birds of Southeastern Victoria Island and adjacent small islands''. National Museum of Canada Bulletin 222.</ref> The laying of a clutch of 11 eggs can take 20–30 days, while a more typical nest of around 8 takes about up to 16 days.<ref name= Voous/><ref name= Bent/> The interval between the 8th and 9th eggs can be up to about 4 days.<ref name= Robinson/> Incubation begins with the first egg and is by female alone, while she is fed by her mate.<ref name= Konig/> ===Parental behavior=== [[File:SnowyOwl2.jpg|thumb|left|A captive mother snowy owl with its chick.]] Food is brought to the nest by males and surplus food is stored nearby.<ref name= Konig/> Females in breeding season often develop a very extensive [[brood patch]] which in this species is a fairly enormous, high vascularized featherless area of pink belly skin.<ref name= Voous/><ref name= Parmelee/> Incubation lasts 31.8–33 days (unconfirmed and possibly dubious reports from as little as 27 to as much as 38-day incubations).<ref name= Konig/><ref name= Murie/><ref name= Robinson/><ref name= Schaanning/> The female alone broods the young, often while simultaneously incubating still unhatched eggs.<ref name= Konig/><ref name= Holt/> Sometimes older chicks incidentally brood their younger siblings and females may shelter the young under her wings during inclement weather.<ref name= Parmelee/><ref name= Watson/> When first feeding the young, the female may dismantle prey to feed the young only the softer body parts then gradually ramping up the size of proportions until they eat a whole prey item.<ref name= Watson/> Aggressive encounters with parent snowy owls are said to be "genuinely dangerous" and one resource claimed the snowy owl to be the bird species with the most formidable nest defense displays towards humans.<ref name= Voous/><ref name= Bent/><ref>Couzens, D. (2008). ''Extreme Birds: The World's Most Extraordinary and Bizarre Birds''. Firefly Books.</ref> The usual response to sighted humans near the nest is mild but continued approach begins to increasingly irritate the parents.<ref name= Holt/> At times, humans are forcefully dive-bombed upon, while other potential threats are dealt with in a “forward-threat” where the male walks towards the intruders, engaging in impressive feather-raising and fanning out of half-spread wings until they run forward and slash with both their feet and bill.<ref name= Voous/><ref name= Bent/><ref name= Watson/><ref name= Sutton1/><ref name= Parmelee/> Fairly serious injuries have been sustained in the worst of snowy owl defensive attacks, including cranial trauma, requiring researchers to make the long trek back to medical care, although human fatalities are not known.<ref name= Sutton/> Snowy owl parents have been seen to aggressively attacked glaucous gulls, arctic fox and dogs in breeding ground in Utqiaġvik.<ref name= Holt/> Non-predatory animals like [[Reindeer|caribou]] in Utqiaġvik and sheep (''Ovis aries'') in Fetlar are attacked as well, possibly to avoid potential trampling of the eggs or the young.<ref name= Parmelee/><ref name= Tulloch/> Males are said to do the majority of nest defense but the female will also often become involved as well.<ref name= Holt/> Analysis showed in [[Lapland, Sweden]], that females in nest defense against people engaged in vocal displays (warning and mewing calls) and that males did not engage in mewing but did engage in most hooting calls, many warning calls and almost all physical attacks.<ref name= Wiklund>{{cite journal|title=Nest defence and evolution of reversed sexual size dimorphism in Snowy Owls ''Nyctea scandiaca''|doi=10.2307/3676252}}</ref> In other instances, [[distraction display]]s are engaged in against predators, with a "broken-wing act" including high, thin squeals interspersed with weird squeaks, often taking flight only to quickly fall from the sky and imitate a struggle.<ref name= Voous/><ref>[http://animaldiversity.ummz.umich.edu/site/accounts/information/Nyctea_scandiaca.html ADW: ''Nyctea scandiaca: Information'']. Animaldiversity.ummz.umich.edu. Retrieved on 19 October 2010.</ref> One author recorded a male to draw him about {{convert|2|km|mi|abbr=on}} from the nest before ceasing.<ref name= Parmelee/> 77% of 45 distraction displays in Lapland, Sweden were by females.<ref name= Wiklund/> ===Development of young=== [[File:Young snowy owls (69120).jpg|thumb|An old photo of snowy owl nestlings on [[Baffin Island]].]] Hatching intervals are generally from 1 to 3 days, quite often within 37–45 hours apart.<ref name= Watson/><ref name= Tulloch/> New chicks are [[Altriciality|semi-altricial]] (i.e. typically helpless and blind), initially being white and rather wet but dry by the end of the first day. The weight of 7 hatchlings was {{convert|35|to|55|g|oz|abbr=on}}, with an average of {{convert|46|g|oz|abbr=on}} while 3 were {{convert|44.7|g|oz|abbr=on}}.<ref name= Parmelee/><ref name= Watson/> Due to the pronounced asynchrony of the egg-laying and hatching, the size difference between siblings can be enormous and in some cases when the smallest chick weighs only {{convert|20|to|50|g|oz|abbr=on}}, the biggest chick already has attained a weight of around {{convert|350|to|380|g|oz|abbr=on}}.<ref name= Watson/> When the oldest chick is about 3 weeks, the female will start to hunt as well as the male and both may directly feed the young although in some cases they may not need hunt very much if lemmings are particularly numerous.<ref name= Konig/><ref name= Voous/> [[Hoarding (animal behavior)|Caches]] of lemmings around a nest may include more than 80 lemmings that can support the family.<ref name= Voous/> Unlike many owls, the chicks of snowy owls are not known to behave aggressively toward one another or to engage in [[siblicide]], perhaps in part due to the need for energy conservance.<ref name= Holt/><ref name= Tulloch/> Some cases of [[cannibalism]] of chicks by the family group were thought to be cases where chicks die from other causes.<ref name= Sutton/> When they are about 2 weeks, the chicks may begin to walk around the nest site which they leave by 18–28 days, although they are still unable to fly and may find safety in nooks and crannies of vegetation and rocks usually only about {{convert|1|to|2|m|ft|abbr=on}} from the nest mound, as well as via their parents defense.<ref name= Konig/><ref name= Voous/><ref name= Romero>Romero, L. M., Holt, D. W. Maples M. & Wingfield, J. C.. (2006). ''Corticosterone is not correlated with nest departure in Snowy Owl chicks (Nyctea scandiaca)''. General and Comparative Endocrinology 149 (2): 119–123.</ref> Leaving the nest is thought to likely be an anti-predator strategy.<ref name= Holt/><ref>Holt, D. W. & Leasure, S. M. (1993). ''Short-eared Owl (Asio flammeus)''. In: ''The birds of North America, No. 62'', edited by A. Poole and F. Gill. Washington, DC: Acad. Nat. Sci., Philadelphia, PA; Am. Ornithol. Union.</ref> The male snowy owl may drop fresh prey deliveries directly on the ground near the wandering young.<ref name= Voous/> After about three weeks of age, the young may wander fairly widely, rarely to {{convert|1|km|mi|abbr=on}}, but usually stay within {{convert|500|m|ft|abbr=on}} of the nest mound.<ref name= Watson/><ref name= Tulloch/> Threat postures by young in reaction to researchers were first noticeable at about 20–25 days of age and common at about 28 days and the chicks can be impressively quick and agile-footed.<ref name= Holt/><ref name= Watson/> The first fledgling occurs at around 35–50 days, and by 50–60 days the young can fly well and hunt on their own.<ref name= Konig/><ref name= Voous/> The total care period is for 2–3.5 months, increasing in length with increased size of the brood.<ref name= Konig/><ref name= Parmelee/> Although independence was once thought to be sought by late August or early September but is more likely by late September to October when migration season for the species begins.<ref name= Holt/><ref name= Pitelka2/> The nesting cycle is similar in length to the Arctic short-eared owls and faster than Eurasian eagle-owls by up to 2 months.<ref name= Schrezinger>Schrezinger, W. (1974). ''Zur Ethologie und Jugendentwicklung der Schnee-Eule Nyctea scandiaca nach Beobachtungen in Gefangenschaft''. J. Orn, 115: 8–49.</ref> ===Maturity and nesting success=== [[File:SNOWY OWL, Canada.jpg|thumb|left|Snowy owl, juvenile, in Ontario, Canada.]] Sexual maturity reached the following year but the first breeding is normally at no sooner than the end of the second year of life.<ref name= Konig/> There is little strong evidence of typical age of first breeding but initial breeding by males could be inferred by the plumage of males in Utqiaġvik by plumage. At that stage, which the males were essentially all pure white, most were aged to about 3 to 4 years old.<ref name= Holt/> The snowy owl seems to markedly inconsistent in regard to breeding every year, often taking at least up to two years between attempts and sometimes as much as nearly a decade.<ref name= Potapov/> 7 satellite-marking females in Canada proved that they did breed in consecutive years, with 1 breeding over 3 consecutive years.<ref name= Therrien/> In 23 years at Utqiaġvik, snowys bred in 13 of them.<ref name= Holt/> Nesting success can reach 90–100% in even the largest clutches in high lemming years.<ref name= Voous/> While over the course of 21 years, 260 total nests were recorded in Utqiaġvik. There, from 4–54 nests were recorded annually. The Utqiaġvik nests bore 3 to 10 sized-clutches with a mean of 6 eggs per nest and an annual mean hatching success from 39 to 91%. 31–87% of chicks were able to depart on foot and 48–65% were annually estimated to survive to fledge; elsewhere, 40% survived to fledge.<ref name= Holt/><ref name= Parmelee/> In another set, 97% of observed eggs both hatched and fledged.<ref name= Watson/> In Norway, the fledging success from 10 nests was much lower at about 46%.<ref name= Hagen/> Norwegian data, which previously indicated it to be an almost accidental breeder in northern Norway, indicates that it is a more regular breeder than expected, though. 3 good years were found for snowy owls between 1968 and 2005: 1974 (when there were 12 pairs), 1978 (22 pairs) and 1985 (20 pairs), with 14 additional locations when potential (but not confirmed) breeding has occurred. The main determinable causes of nest failure were deemed to be [[starvation]] and [[Hypothermia|exposure]].<ref name= Holt/> A number of Norwegian and Finnish nests were known to fail due to severe [[black fly]] parasitism.<ref>{{cite journal|doi=10.15845/on.v36i0.394}}</ref> ==Longevity== The snowy owl can live a long life for a bird.<ref name= Holt/> Records show that the oldest snowy owls in captivity can live to 25 to even 30 years of age.<ref name= Konig/><ref name= Holt/><ref>Schenker, A. (1978). Höchsalter europaischer Vögel im Zoologischen Garten Basel. Ornithol. Beob. 75: 96–97.</ref> Typical lifespans probably reach around 10 years in the wild.<ref name= Konig/><ref name= Mikkola/> The longest known lifespan in the wild was one that initially banded (possibly in its first winter) in [[Massachusetts]] and recovered dead in [[Montana]] 23 years and 10-month later.<ref name= Holt/> The annual survival rate for twelve females on [[Bylot Island]] was estimated at around 85–92.3%.<ref>{{cite journal|doi=10.1002/jwmg.414}}</ref> It is often reputed that snowy owls frequently died from starvation, with historical accounts frequently opined they "had to" leave their breeding grounds due to lemming "crashes" but would starve to the south.<ref name= Kerlinger/><ref name= Gross1/><ref name= Zettenberg>{{cite journal|doi=10.1898/NWN07-19.1}}</ref> However, it was proven fairly early on that snowy owls often do survive throughout the winter.<ref name= Bent/> This is reinforced somewhat by small radio-tracking and banding studies of the northern [[Great Plains]] and the intermountain [[valley]]s of the northwestern United States.<ref name= Zettenberg/><ref name= Kerlinger3>{{cite journal|doi=10.2307/1368844}}</ref> More circumstance evidence shows a lack of starvation in the eastern part of North America as well.<ref>{{cite journal|title=Winter irruptive Snowy Owls (''Bubo scandiacus'') in North America are not starving|doi=10.1139/cjz-2017-0278|url=https://www.researchgate.net/publication/322843463_Winter_irruptive_snowy_owls_in_North_America_are_not_starving}}</ref> There is evidence that some adults are known to return to the same wintering areas in ensuing years, areas which are far south of their breeding range.<ref>{{cite journal|doi=10.29173/bluejay1721}}</ref><ref>{{cite journal|author1=Follen, D. |author2= Luepke, K. |year=1980|title= Snowy Owl recaptures|journal= Inland Bird Banding |volume=52|pages= 60}}</ref> At Logan Airport, most snowy owls that are seen appear to be in good condition.<ref name= Holt/> Of 71 dead snowy owls found in winter in the northern Great Plains, 86% died from assorted [[Major trauma|traumas]], including [[Roadkill|collisions]] with automobiles and other, usually manmade, objects as well as [[electrocution]]s and [[Culling|shootings]]. Only 14% of the 71 deaths were due to apparent starving. Data showed some owls appeared to incur injuries but healed and survived.<ref name= Kerlinger3/> More evidence was found in wintering snowy owls in New York of [[Bone healing|healed fractures]], though some may require surgery to recover.<ref>{{cite journal|pmid=30204018|title=Successful Management of Open, Contaminated Metacarpal Fractures in an Adult Snowy Owl (''Bubo scandiacus'') With a Minimal Type II External Skeletal Fixator}}</ref> 537 wintering birds in Saskatchewan were studied based on [[Fatty acid metabolism|fat reserves]], which were superior in females over males and adults over juveniles; while 31% of females lacked fat reserves, at least 45% of males found starving or in a state of infirmity were males and 63% turned into [[Wildlife rehabilitation]] centres were also males.<ref name= Chang/> In British Columbia, of 177 snowy owl deaths, of owls to die, only a small percentage were due to natural causes, such as assumed starvation at 13% and 12% were "found dead".<ref name= Campbell/> 1 fledgling on Fetlar dead due to [[pneumonia]] and ''[[Staphylococcus]]'' while a second died from ''[[Aspergillosis]]''.<ref name= Robinson/> Evidence shows that in Utqiaġvik during exceptionally prolonged rains (i.e. 2 to 3 days), nest-departed young in Utqiaġvik were vulnerable to starvation, leading to [[hypothermia]] and pneumonia.<ref name= Holt/> Due to their natural history, the snowy owl may be effected more severely by [[Parasitism|blood parasitism]] than other raptors, due to lowered [[Immunity (medical)|immunity]].<ref>{{cite journal|pmid=29517448|title=Clinical effect of hemoparasite infections in snowy owls (''Bubo scandiacus'')}}</ref> Conversely, they appear to have lower levels of ectoparasites like [[Mallophaga|chewing lice]] than in other large owls per large samples from [[Manitoba]]. The snowy owls averaged about 3.9 chewing lice per host against 7.5 for great grey owls and 10.5 for great horned owls.<ref>{{cite journal|doi=10.4039/tce.2019.42|title=Infestation parameters for chewing lice (Phthiraptera: Amblycera, Ischnocera) infesting owls (Aves: Strigidae, Tytonidae) in Manitoba, Canada}}</ref> ==Status== This species presence and numbers is dependent on amount of food available. In "lemming years", snowy owls can appear to be quite abundant in habitat.<ref name= Konig/> Numbers of snowy owls are difficult to estimate even within studies that take place over decades due to the nomadic nature of adults.<ref name= Holt/> The population of [[Scandinavia]] has long been perceived as very small and [[Ephemerality|ephemeral]] with Finland holding 0–100 pairs; Norway holding 1–20 pairs and Sweden holding 1–50 pairs.<ref name= Holt/><ref name= Saurola>{{cite journal|doi=10.5253/078.097.0411}}</ref> A low breeding population within [[European Russia]] has been estimated to hold 1,300–4,500 pairs and Greenland to have 500–1,000 pairs.<ref>BirdLife International (2015). ''European Red List of Birds''. Office for Official Publications of the European Communities, Luxembourg</ref><ref>{{cite journal|doi=10.3312/jyio.44.1|title=Cross-species amplification of microsatellite markers in the Great Horned Owl ''Bubo virginianus'', Short-eared Owl ''Asio flammeus'' and Snowy Owl ''B. scandiacus'' for use in population genetics, individual identification and parentage studies}}</ref> Other than northern part of the American continent, a majority of the snowy owl's breeding range is in northern Russia, but overall estimates are not known.<ref name= Holt/><ref>Stepanyan, L.S. (1990). ''Konspekt ornitologicheskoi fauny SSSR. [Conspectus of the Ornithological Fauna of the USSR]''. Nauka, Moscow. (In Russian with English summary.).</ref> An exact count of 4,871 individuals were seen on surveys between the [[Indigirka River|Indigirka]] and [[Kolyma river]]s.<ref name= Potapov/> The numbers estimated by Partners in Flight and other authors by the 2000s was that North America held about 72,500 snowy owls, about 30% of which were juveniles.<ref>Rich, T. D., Beardmore, C. J. Berlanga, H., Blancher, P. J., Bradstreet, M. S. W., Butcher, G. S., Demarest, D. W., Dunn, E. H., Hunter, W. C., Iñigo-Elias, E. E., Kennedy, J. A., Martell, A. M.. Panjabi, A. O., Pashley, D. N., Rosenberg, K. V., Rustay, C. M., Wendt, J. S. & Will, T. C. (2004). ''Partners in Flight North American Landbird Conservation Plan''. Cornell Lab of Ornithology, Ithaca, NY, USA.</ref><ref>{{cite journal|doi=10.2193/0091-7648(2006)34[1392:EOFHOW]2.0.CO;2}}</ref> The Canadian population of snowy owls was estimated at 10,000–30,000 (in the 1990s) or even to 50,000–100,000 individuals, perhaps improbably.<ref>{{cite journal|author=Kirk, D. A., Hussell D. & Dunn, E. |year=1995|title=Raptor population status and trends in Canada|journal= Bird Trends|volume= 4|pages= 2–9}}</ref><ref>Reding-License, A. A. (2015). Harfang des neiges (''Bubo scandiacus''). Government of Canada.</ref><ref>American Ornithologists' Union (1998). ''Check-list of North American Birds, 7th edition''. American Ornithologists' Union, Washington, DC, USA.</ref> Within Canada, the population on [[Banks Island]] was once claimed at up to 15,000–25,000 in productive years and in [[Queen Elizabeth Islands]] at about 932 individuals.<ref name= Manning/><ref>Miller, F. L. (1987). ''Snowy Owl numbers on twelve Queen Elizabeth Islands, Canadian High Arctic''. Journal of Raptor Research 21 (4): 153–157.</ref> Alaska is the only state with breeding snowy owls but has probably quite a bit fewer breeding owls than does Canada.<ref>Alaska Department of Fish and Game. State of Alaska special status species 2011.</ref> Furthermore, the Partners in Flight and the [[IUCN]] estimated that the world population was roughly 200,000–290,000 individuals as recently as the 2000s.<ref>PIFSC. ''Partners in Flight Science Committee (2013)''. Population estimates database (Version 2.0) 2013. Available from http://rmbo.org/pifpopestimates.</ref><ref>BirdLife International. ''Nyctea Scandiaca''. 2006 IUCN Red List of Threatened Species (2004). Available from http://www.iucnredlist.org.</ref><ref>Burton, J. A. (1973). ''Owls of the world''. New York: E. P. Dutton.</ref> However, in the 2010s, it has been discovered that all prior estimates were extremely excessive and that more precise numbers could be estimated with better surveying, [[Phylogeography|phylogeographic data]] and more insights into the owl's free-wheeling wanderings.<ref name="iucn status 19 November 2021" /><ref name= Holt/> It is now believed that there are only 14,000–28,000 mature breeding pairs of snowy owls in the world.<ref name= Holt/><ref name= Marthinsen/> During lemming declines, the number of nesting females may drop down to as low as 1,700 worldwide, a dangerously low number, and the number of snowy owls worldwide is less than 10% of what it was once thought to be.<ref name= Holt/><ref name= Marthinsen/><ref name=chitty>{{cite journal|doi=10.2307/1527}}</ref> Due to the small and rapidly declining population, the snowy was uplisted in 2017 to being a [[vulnerable species]] by the [[IUCN]].<ref name="iucn status 19 November 2021" /> A 52% decline has been inferred for the North American population since the 1960s with another even more drastic estimate placing the decline from 1970 to 2014 at 64%.<ref>{{cite journal|doi=10.1650/CONDOR-17-57.1}}</ref> Trends are harder to delineate in Scandinavia but a similar downward trend is thought to be occurring.<ref name= Holt/><ref name= Saurola/> ===Anthropogenic mortality and persecution=== [[File:Snowy Owl, Gerald R. Ford Int&#039;l Airport, Grand Rapids, MI, 5 December 2013 (11230541096).jpg|thumb|left|Snowy owls often favor airports, such as this one at [[Gerald R. Ford International Airport]], in winter but the risk of [[birdstrike]] is high in such areas.]] Of 438 band encounters in the USG banding laboratory, almost all causes of death that could be determined, whether intentional or not, were correlated with human interference.<ref name= Holt/> 34.2% or 150 were dead due to unknown causes, 11.9% were shot, 7.1% were hit by automobiles, 5.5% were found dead or injured on highways, 3.9% were collision from towers or wires, 2.7% were in animal traps, 2.1% in airplane [[birdstrike]]s, 0.6% were [[Wire obstacle|entangled]] while the remaining 33.3% recovered injured due to assorted or unknown causes.<ref name= Holt/> Snowy owls are endangered by heavy airport usage resulting in [[birdstrike]]s. Many such collisions are known in Canada and likely also in [[Siberia]] and Mongolia .<ref name= Catling>{{cite journal|author=Catling, P. M. |year=1973|title=Food of snowy owls wintering in southern Ontario, with particular reference to the snowy owl hazard to aircraft|journal=Ontario field biol|volume= 7|pages= 41–45}}</ref><ref>{{cite journal|doi=10.2307/1367598}}</ref> Despite their danger to planes, no human fatalities have been recorded in collisions with this species.<ref>Blokpoel, H. (1976). ''Bird hazards to aircraft: problems and prevention of bird/aircraft collisions''. Clarke Irwin;[Ottawa]: Canadian Wildlife Service, Environment Canada: Pub. Centre, Supply and Services Canada.</ref> Snowy owls are always far outnumbered in Canadian airports in winter by [[short-eared owl]]s.<ref name= Voous/> However, relative to its scarcity, the snowy accounts for a very large balance of the birdstrikes recorded at American airports due to the attractiveness of the habitat, accounting for 4.6% of 2456 recorded collisions (the barn owl is the most frequently involved in birdstrikes).<ref name= Linnell>{{cite journal|doi=10.3356/JRR-17-64.1}}</ref> The species is locally vulnerable to [[pesticide]]s.<ref name= Konig/> The placement of buildings in the Utqiaġvik is now thought to have displaced some snowy owls.<ref name= Holt3/> In Norway, potential sources of disturbance near the nests include tourism, [[recreation]], [[Reindeer herding|reindeer husbandry]], [[Traffic|motorized traffic]], dogs, photographers, ornithologists and scientists.<ref name= Heggoy/> Some biologist have expressed concern that [[Telemetry|radio-tagging]] of snowy owls may cause some unclear detrimental effect on snowy owls but little evidence is known if they actually make the owls more susceptible to death.<ref>{{cite journal|doi=10.15845/on.v40i0.1309|title=Effects of satellite transmitters on survival in Snowy Owls ''Bubo scandiacus''}}</ref> Snowy owls can be quite wary, as they are not infrequently hunted by [[Circumpolar peoples]].<ref name= Voous/> Historically, the snowy owl was one of the most persecuted owl species.<ref name= Holt/> In the irruption of 1876–77, an estimated 500 snowy owls were shot, with similar numbers in 1889–90 and an estimated 500–1,000 killed in [[Ontario]] alone during 1901–02 invasion and about 800 killed in the 1905–06 invasion.<ref name= Bent/> Indigenous people of the Arctic historically killed snowy owls as food but now many communities in northern Alaska are fairly modernized, therefore biologists feel that the permitted killing of snowy owls by the indigenous is outdated.<ref name= Holt/><ref>{{cite journal|url=https://brooklynworks.brooklaw.edu/bjil/vol30/iss2/6/|author=Bakalar, E. M. |year=2004|title=Subsistence Whaling in the Native Village of Barrow: Bringing Autonomy to Native Alaskans Outside the International Whaling Commission|journal= Brook. J. Int'l L.|volume= 30|pages= 601}}</ref> The consumption of snowy owls by humans has been proven as far back as ancient cave deposits in France and elsewhere, and they have even been considered as one of the most frequent food species for early humans.<ref>{{cite journal|url=https://www.researchgate.net/publication/285483173_La_chasse_aux_oiseaux_pendant_la_Prehistoire|author=Mourer-Chauviré, C. |year=1979|title=La chasse aux oiseaux pendant la Préhistoire|journal= La Recherche|volume= 106|issue=10|pages= 1202–1210}}</ref><ref>{{cite journal|doi=10.1016/J.QUAINT.2015.11.146|title=Hunting fast-moving, low-turnover small game: The status of the snowy owl (''Bubo scandiacus'') in the Magdalenian}}</ref> They do not shun developed areas especially with old field that hold rodents and, due to lack of human experience, can be extremely tame and unable to escape armed humans.<ref name= Voous/> In British Columbia, of 177 snowy owl deaths, the most often diagnosed cause of death was shootings at 25%, often well after legal protection of the species.<ref name= Campbell/> The number [[Poaching|poached]] snowy owls in Ontario is opined to be unusually high considering their scarcity.<ref name= Desmarchelier>Desmarchelier, M., Santamaria-Bouvier, A., Fitzgérald, G., & Lair, S. (2010). ''Mortality and morbidity associated with gunshot in raptorial birds from the province of Quebec: 1986 to 2007''. The Canadian Veterinary Journal, 51(1), 70.</ref> While the species was once otherwise killed as food and then later shot out of resentment for perceived threats against domestic and favored game stock, the reasoning behind ongoing shooting of snowy owls into the 21st century is not well-understood.<ref name= Holt/><ref name= Dufresne/><ref name= Desmarchelier/> Siberian snowy owls are frequently victim to [[Bait (luring substance)|baited]] [[Trapping|fox traps]], with possibly up to around 300 killed in a year based upon very rough estimates.<ref>{{cite journal|author=Ellis, D. H. & D. G. Smith|year=1993|title=Preliminary report of extensive Gyrfalcon and Snowy Owl mortality in northern Siberia|journal= Raptor-Link |volume=1 |issue=2|pages=3–4}}</ref> [[Warfarin]] poisoning in use as [[rodenticide]]s are known to kill some wintering snowy owls, including up to six at Logan Airport alone.<ref name= Campbell/><ref>{{cite journal|author=Stone, W. B., Okoniewski, J. C. & Stedelin, J. R. |year=1999|pmid=10231745|title=Poisoning of wildlife with anticoagulant rodenticides in New York|journal= Journal of Wildlife Diseases |volume=35|pages=187–193}}</ref> [[Mercury (element)|Mercury]] concentrations, most likely through [[bioaccumulation]], have been detected in snowy owls in the [[Aleutian Islands]] but it is not known whether fatal [[mercury poisoning]] has occurred.<ref>{{cite journal|doi=10.1016/j.marpolbul.2014.02.034}}</ref> [[Polychlorinated biphenyl|PCB]]s may have killed some snowy owls in concentration.<ref name= Heggoy/> Some airports have advocated and instituted the practice of shooting owls to avoid birdstrikes but successful [[Wildlife translocation|translocation]] is possible and preferred given the species protected status.<ref name= Holt/><ref name= Linnell/> [[File:Stare Down Snowy (94026869).jpeg|thumb|right|A potential high risk of electrocution exists for snowy owls in winter.]] [[Global warming|Climate change]] is now widely perceived to perhaps the primary driver of the snowy owl's decline. As temperatures continue to rise, abiotic factors such as increased rain and reduced snow are likely to effect lemming populations and, in turn, snowy owls. These and potentially many other issues (possibly including modifying migrating behavior, vegetation composition, increased insect, disease and parasite activities, risk of [[hyperthermia]]) are a matter of concern.<ref name="iucn status 19 November 2021" /><ref name= Holt/><ref name= Heggoy/><ref>Inouye, D. W. (2019). "Climate change in other taxa". ''Effects of Climate Change on Birds'', p. 257. {{ISBN|9780198824268}}</ref> Additionally, reduction of sea ice, which snowy owls are now known to rely extensively on, as a result of warming climates, impacts could be significant.<ref name="iucn status 19 November 2021" /><ref name= Holt/><ref name= Marine/> The effect of [[climate change]] was essentially confirmed in northern Greenland where a perhaps irrevocable collapse of the lemming population was observed. From 1998 to 2000, the lemming numbers appeared to have quickly declined. The number of lemmings per hectare (ha) is less than one-fifth of what it once was in Greenland (i.e. from 12 lemmings per ha to less than 2 per ha at peak). This is almost certainly correlated with a 98% decline in owl productivity as well as that of the local [[Stoat|stoats]] (the [[long-tailed jaeger]] and [[Arctic fox]]es, though previously thought to be almost as reliant on lemmings, seem to be more loosely coupled and more generalized and did not decline as much).<ref name= Schmidt>{{cite journal|pmid=22977153}}</ref><ref>{{cite journal|doi=10.4080/gpcw.2011.0113}}</ref> The amount of lemming mounds is much less than it once in northern Greenland and any variety of [[population cycle]] has been apparently abandoned by what remains of the lemmings.<ref name= Schmidt/> ==In popular culture== * The ''[[Harry Potter]]'' books by [[J. K. Rowling]], and subsequent [[Harry Potter (film series)|films]] of the same name, feature a female snowy owl named [[Magical creatures in Harry Potter#Hedwig|Hedwig]].<ref>{{cite web |url=https://www.pottermore.com/features/4-reasons-hedwig-was-better-than-everyone-else-at-hogwarts |title=4 reasons Hedwig was better than everyone else at Hogwarts |publisher=Pottermore |access-date=13 February 2018}}</ref> Concern was expressed by some in the media that the popularity of the Harry Potter films would cause an increase in the [[Black market|illicit]] [[Wildlife trade|owl trade]] of snowy owls. However, there was no strong evidence of an increase in snowy owls confiscated from the black market, despite a larger than typical number of snowy owls being reported at [[Wildlife rehabilitation|wildlife centres]].<ref>{{cite journal|doi=10.1371/journal.pone.0182368}}</ref> * The [[EADS Harfang]], [[drone aircraft]] developed by the [[French Air Force]], is named in French for the snowy owl (''Harfang des neiges''). * The snowy owl ({{lang|fr|[[wikt:harfang des neiges|harfang des neiges]]}} in French) is the avian symbol of [[Quebec]].<ref>{{cite web|url=https://en.refugepageau.ca/snowy-owl|title=The avian emblem of Quebec|work=Refuge Pageau}}</ref> == References == {{Reflist|30em}} == External links == {{Commons|Bubo scandiacus}} {{Wikispecies|Bubo scandiacus}} * [https://web.archive.org/web/20080724094156/http://www.explorebiodiversity.com/BIRDS/BirdsofWorld/video/SnowyOwl/video.html Free Video About Snowy Owls] * [https://www.theguardian.com/environment/2015/jan/08/snowy-owl-increasingly-casting-spell-north-american-skies Snowy owl increasingly casting its spell over North American skies] (Jan. 2015), ''[[The Guardian (UK)|The Guardian]]'' * [http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/Snowy_Owl.html Snowy Owl Species Account]—Cornell Lab of Ornithology * [https://web.archive.org/web/20150225091841/http://www.mbr-pwrc.usgs.gov/id/framlst/i3760id.html Snowy Owl – ''Nyctea scandiaca'']—USGS Patuxent Bird Identification InfoCenter * {{Avibase|name=Bubo scandiacus}} * {{InternetBirdCollection|snowy-owl-nyctea-scandiaca|Snowy Owl}} * {{VIREO|Snowy+Owl|Snowy Owl}} {{Taxonbar |from=Q170177}} {{DEFAULTSORT:owl, snowy}} [[Category:Bubo (genus)|snowy owl]] [[Category:Birds of the Arctic]] [[Category:Birds of Scandinavia]] [[Category:Holarctic birds]] [[Category:Birds of Manchuria]] [[Category:Birds described in 1758|snowy owl]] [[Category:Provincial symbols of Quebec]] [[Category:Taxa named by Carl Linnaeus|snowy owl]]'
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'@@ -83,5 +83,5 @@ ==Behavior== [[File:Bubo scandiacus Delta 6.jpg|thumb|right|Juvenile owls do not mind associating with one another, especially during winter.]] -Snowy owls may be active to some extent at both day, from dawn to dusk, and night.<ref name= Konig/><ref name="Manniche" /> Snowy owls have been seen to be active even during the very brief winter daytime in the northern winter.<ref name= Voous/> During the Arctic summer, snowy owls may tend to peak in activity during the twilight that is the darkest time available given the lack of full nightfall.<ref name= Voous/><ref>Young, C.M. (1973). ''The Snowy Owl migration of 1971–72 in the Sudbury region of Ontario''. American Birds 27(1): 11–12.</ref><ref>Shields, M. (1969). ''Activity cycles of Snowy Owls at Barrow, Alaska''. Murrelet 50 (2): 14–16.</ref> Reportedly, the peak time of activity during summer is between 9:00&nbsp;pm and 3:00&nbsp;am in Norway.<ref name= Hagen>Hagen, Y. (1960). ''The Snowy Owl on Hardangervidda in the Summer of 1959''. Papers of The Norwegian State Game Research. 2, No. 7.</ref> The peak time of activity for those owls that once nested on Fetlar was reported between 10:00 and 11:00&nbsp;pm.<ref name= Tulloch>Tulloch, R. J. (1968). ''Snowy Owls breeding in Shetland in 1967''. British Birds 61:119–132.</ref> According to one authority, the least active times are at noon and midnight.<ref name= Watson/> As days become longer near autumn in [[Utqiaġvik, Alaska|Utqiaġvik]], the snowy owls in the tundra become more active around nightfall and can often be seen resting during the day, especially if it is raining.<ref>Shields, M. (1969). ''Activity cycles of Snowy Owls at Barrow, Alaska''. Murrelet 50 (2):14–16.</ref> During winter in [[Alberta]], snowy owls were tracked in the daytime, despite being also active at night (as they were deemed too difficult to track). In the study, they were most active from 8:00–10:00&nbsp;am and 4:00–6:00&nbsp;pm and often rested mostly from 10:00&nbsp;am to 4:00&nbsp;pm. The owls were perched for 98% of observed daylight and seemed to time their activity to peak times for rodents.<ref>Boxall, P. C. & Lein, M. R. (1989). ''Time budgets and activity of wintering Snowy Owls''. Journal of Field Ornithology 60 (1): 20–29.</ref> The variation of activity is probably in correspondence with their primary prey, the [[lemming]]s, and like them, the snowy owl may be considered [[Cathemerality|cathermal]].<ref name= Konig/><ref name= Voous/><ref name="National Geographic">{{cite web|title=Snowy Owl (Nyctea Scandia)|url=http://animals.nationalgeographic.com/animals/birds/snowy-owl/|website=animals.nationalgeographic.com|publisher=National Geographic|date=11 November 2010}}</ref> This species can withstand extremely cold temperatures, having been recorded in temperatures as low as minus 62.5 [[Celsius|degrees Celsius]] with no obvious discomfort and also withstood a 5-hour exposure to minus 93 degrees Celsius but may have struggled with oxygen consumption by the end of this period. The snowy owl has perhaps the second lowest [[thermal conduction]] to the plumage on average of any bird after only the [[Adelie penguin]] (''Pygoscelis adeliae'') and rivals the best insulated mammals, such as [[Dall sheep]] (''Ovis dalli'') and [[Arctic fox]], as the best insulated polar creature.<ref name= Voous/><ref name= Gessaman>Gessaman, J. A. (1972). ''Bioenergetics of the snowy owl (Nyctea scandiaca)''. Arctic and Alpine Research, 4(3), 223–238.</ref><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/condor/v057n06/p0362-p0365.pdf|author=Irving, L. |title=Nocturnal decline in the temperature of birds in cold weather|doi=10.2307/1364794}}</ref> Presumably as many as 7 rodents would need to be eaten daily to survive an extremely cold winter's day.<ref name= Voous/> Adults and young both have been seen to shelter behind rocks to shield themselves from particularly harsh winds or storms.<ref name= Holt/> Snowy owls often spending a majority of time on the ground, perched mostly on a slight rise of elevation.<ref name= Konig/> It has been interpreted from the morphology of their skeletal structure (i.e. their short, broad legs) that snowy owls are not well-suited to perching extensively in trees or rocks and prefer a flat surface to sit upon.<ref name= Potapov/> However, they may perch more so in winter though do so only mainly when hunting, at times on [[hummock]]s, [[Fence]]posts, [[telegraph pole]]s by roads, [[Radio tower|radio]] and [[transmission tower]]s, [[Hay]]stacks, [[chimney]]s and the roofs of houses and large buildings.<ref name= Voous/> Rocks may be used as perches at times in all seasons.<ref name= Voous/> Though often relatively sluggish owls, like most related species, they are capable of sudden dashing movements in various contexts.<ref name= Potapov/> Snowy owls can walk and run quite quickly, using outstretched wings for balance if necessary.<ref name= Konig/> This owl flies with fairly rowing wingbeats, occasionally interrupted by gliding on stretched wings. The flight is fairly buoyant for a ''Bubo'' owl.<ref name= Konig/><ref name= Holt/> When displaying, the male may engage in an undulating flight with interspersed wingbeats and gliding in a slight dihedral, finally dropping rather vertically to the ground.<ref name= Konig/> They are capable for swimming but do not usually do so. Some seen to be swimming were previously injured but young have been seen to swim into water to escape predators if they cannot fly yet. They will also drink when unfrozen water is available.<ref name= Holt/><ref name= Tulloch/><ref>Mebs, T. & Scherzinger, W. (2000). ''Snowy Owl''. In: ''Die eulen Europa: biolgie, kennzeichen, bestande'', edited by T. Mebs and W. Scherzinger, 167–183. Stuttgart: Franckh-Kosmos Verlags-Gmbh and Co.</ref> Snowy owl mothers have been observed to [[Preening (bird)|preen]] their young in the wild, while pairs in captivity have been observed to allopreen.<ref name= Watson/> In the period leading up to breeding, snowy owls switched regularly between searching (for nesting grounds) and loafing, often searching less when snow cover was less extensive.<ref>Therrien, J. F., Pinaud, D., Gauthier, G., Lecomte, N., Bildstein, K. L., & Bety, J. (2015). ''Pre-breeding prospecting behaviour of snowy owls'' (data from Therrien et al. 2015)-reference-data.</ref> +Snowy owls may be active to some extent at both day, from dawn to dusk, and night.<ref name= Konig/> Snowy owls have been seen to be active even during the very brief winter daytime in the northern winter.<ref name= Voous/> During the Arctic summer, snowy owls may tend to peak in activity during the twilight that is the darkest time available given the lack of full nightfall.<ref name= Voous/><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/nab/v027n01/p00011-p00012.pdf|author=Young, C.M. |year=1973|title=The Snowy Owl migration of 1971–72 in the Sudbury region of Ontario|journal= American Birds |volume=27|issue=1|pages= 11–12}}</ref><ref name=shields>{{cite journal|doi=10.2307/3536292}}</ref> Reportedly, the peak time of activity during summer is between 9:00&nbsp;pm and 3:00&nbsp;am in Norway.<ref name= Hagen>Hagen, Y. (1960). ''The Snowy Owl on Hardangervidda in the Summer of 1959''. Papers of The Norwegian State Game Research. 2, No. 7.</ref> The peak time of activity for those owls that once nested on Fetlar was reported between 10:00 and 11:00&nbsp;pm.<ref name= Tulloch>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V61/V61_N03/V61_N03_P119_132_A019.pdf|author=Tulloch, R. J. |year=1968|title=Snowy Owls breeding in Shetland in 1967|journal= British Birds|volume= 61|pages=119–132}}</ref> According to one authority, the least active times are at noon and midnight.<ref name= Watson/> As days become longer near autumn in [[Utqiaġvik, Alaska|Utqiaġvik]], the snowy owls in the tundra become more active around nightfall and can often be seen resting during the day, especially if it is raining.<ref name=shields/> During winter in [[Alberta]], snowy owls were tracked in the daytime, despite being also active at night (as they were deemed too difficult to track). In the study, they were most active during 8:00–10:00&nbsp;am and 4:00–6:00&nbsp;pm and often rested mostly from 10:00&nbsp;am to 4:00&nbsp;pm. The owls were perched for 98% of observed daylight and seemed to time their activity to peak times for rodents.<ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/jfo/v060n01/p0020-p0029.pdf|author1=Boxall, P. C. |author2= Lein, M. R. |year=1989|title=Time budgets and activity of wintering Snowy Owls|journal= Journal of Field Ornithology |volume=60 |issue=1|pages= 20–29}}</ref> The variation of activity is probably in correspondence with their primary prey, the [[lemming]]s, and like them, the snowy owl may be considered [[Cathemerality|cathermal]].<ref name= Konig/><ref name= Voous/><ref name="National Geographic">{{cite web|title=Snowy Owl (Nyctea Scandia)|url=http://animals.nationalgeographic.com/animals/birds/snowy-owl/|website=animals.nationalgeographic.com|publisher=National Geographic|date=11 November 2010}}</ref> This species can withstand extremely cold temperatures, having been recorded in temperatures as low as minus 62.5 [[Celsius|degrees Celsius]] with no obvious discomfort and also withstood a 5-hour exposure to minus 93 degrees Celsius but may have struggled with oxygen consumption by the end of this period. The snowy owl has perhaps the second lowest [[thermal conduction]] to the plumage on average of any bird after only the [[Adelie penguin]] (''Pygoscelis adeliae'') and rivals the best insulated mammals, such as [[Dall sheep]] (''Ovis dalli'') and [[Arctic fox]], as the best insulated polar creature.<ref name= Voous/><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/condor/v057n06/p0362-p0365.pdf|author=Irving, L. |title=Nocturnal decline in the temperature of birds in cold weather|doi=10.2307/1364794}}</ref> Presumably as many as 7 rodents would need to be eaten daily to survive an extremely cold winter's day.<ref name= Voous/> Adults and young both have been seen to shelter behind rocks to shield themselves from particularly harsh winds or storms.<ref name= Holt/> Snowy owls often spending a majority of time on the ground, perched mostly on a slight rise of elevation.<ref name= Konig/> It has been interpreted from the morphology of their skeletal structure (i.e. their short, broad legs) that snowy owls are not well-suited to perching extensively in trees or rocks and prefer a flat surface to sit upon.<ref name= Potapov/> However, they may perch more so in winter though do so only mainly when hunting, at times on [[hummock]]s, [[Fence]]posts, [[telegraph pole]]s by roads, [[Radio tower|radio]] and [[transmission tower]]s, [[Hay]]stacks, [[chimney]]s and the roofs of houses and large buildings.<ref name= Voous/> Rocks may be used as perches at times in all seasons.<ref name= Voous/> Though often relatively sluggish owls, like most related species, they are capable of sudden dashing movements in various contexts.<ref name= Potapov/> Snowy owls can walk and run quite quickly, using outstretched wings for balance if necessary.<ref name= Konig/> This owl flies with fairly rowing wingbeats, occasionally interrupted by gliding on stretched wings. The flight is fairly buoyant for a ''Bubo'' owl.<ref name= Konig/><ref name= Holt/> When displaying, the male may engage in an undulating flight with interspersed wingbeats and gliding in a slight dihedral, finally dropping rather vertically to the ground.<ref name= Konig/> They are capable for swimming but do not usually do so. Some seen to be swimming were previously injured but young have been seen to swim into water to escape predators if they cannot fly yet. They will also drink when unfrozen water is available.<ref name= Holt/><ref name= Tulloch/><ref>Mebs, T. & Scherzinger, W. (2000). ''Snowy Owl''. In: ''Die eulen Europa: biolgie, kennzeichen, bestande'', edited by T. Mebs and W. Scherzinger, 167–183. Stuttgart: Franckh-Kosmos Verlags-Gmbh and Co.</ref> Snowy owl mothers have been observed to [[Preening (bird)|preen]] their young in the wild, while pairs in captivity have been observed to allopreen.<ref name= Watson/> In the period leading up to breeding, snowy owls switched regularly between searching (for nesting grounds) and loafing, often searching less when snow cover was less extensive.<ref>Therrien, J. F., Pinaud, D., Gauthier, G., Lecomte, N., Bildstein, K. L., & Bety, J. (2015). ''Pre-breeding prospecting behaviour of snowy owls'' (data from Therrien et al. 2015)-reference-data.</ref> [[File:A Snowy Owl in Flight David Hemmings.jpg|thumb|left|Snowy owls are often somewhat ponderous in movements but can be surprisingly and suddenly fast on the wing.]] Snowy owls will fight with conspecifics in all seasons occasionally but this is relatively infrequent during breeding and rarer still during winter. Dogfights and talon interlocking may ensue if the fight between two snowy owls continues to escalate.<ref name= Evans/><ref name= Watson/><ref name= Taylor/> A study determined that snowy owls are able to orient the whitest parts of their plumage towards the sun, spending about 44% of time oriented as such during sunny days and much less on cloudy days. Some authors interpret this as a presumed signal to conspecifics, but [[thermoregulation]] could also be a factor.<ref>Bortolotti, G. R., Stoffel, M. J., & Galvan, I. (2011). ''Wintering Snowy Owls Bubo scandiacus integrate plumage colour, behaviour and their environment to maximize efficacy of visual displays''. Ibis, 153(1), 134–142.</ref><ref>{{cite journal |author1= Wiebe, K. L. |author2= Chang, A. M. | year=2018| title= ''Seeing sunlit owls in a new light: orienting Snowy Owls may not be displaying.'' | journal=Ibis| volume=160| pages=62–70| doi=10.1111/ibi.12533| issue=1}}</ref> It is known that during winter in Alberta that female snowy owls are territorial towards one another and may not leave an area for up to 80 days but males are nomadic, usually only staying 1–2 days in an area (seldom to 3–17 days). The females spent on average seven times as long in a given area than did males.<ref name= Boxall>Boxall, P.C. & Lein, M.R. (1982). ''Are owls regular? An analysis of pellet regurgitation times of Snowy Owls in the wild''. Raptor Research. 16(3): 79–82.</ref> During threat displays, individuals will lower the front of the body, stretch the head low and forward, with partially extended wings and feathers on the head and raise their back.<ref name= Watson/> If continuously threatened or cornered, the posture in the threat display may become still more contoured and, if pressed, the owl will like back and attempt to slash with its large talons. The threat displays of males are generally more emphatic than those of females.<ref name= Holt/><ref>Kaufman, K. (1996). ''Lives of North American Birds''. Houghton Mifflin Company, Boston & New York.</ref> Although snowy owls have been considered as semi-colonial, they do not appear to fit this mold well. Nesting sites can be loosely clustered but this is a coincidental response to concentrated prey and each pair tends to be somewhat intolerant of each other.<ref name= Holt/><ref name= Hart>Hart, H. C. (1880). ''Notes on the ornithology of the British Polar Expedition, 1875-6''. Zoologist 4:121–129.</ref><ref>Brandt, H. (1942). ''Alaska Bird Trails: An Expedition by Dog Sled to the Delta of the Yukon River at Hooper Bay''. The Bird Research Foundation, Cleveland, OH, USA.</ref><ref>Dorogoi, I.V. (1990). ''[Factors of communal breeding of the Snowy Owls (Nyctea scandiaca) and Anseriformes birds at the Vrangel Island]''. Ornitologiya. 24: 26–33. In Russian with English summary.</ref> During winter, snowy owls are usually solitary but some [[Aggregation (ethology)|aggregation]]s have been recorded, especially nearer the Arctic when more narrow food selection can lead to up to 20–30 owls gathering in an area of about {{convert|20|to|30|ha|acre|abbr=on}}.<ref name= Holt/><ref name= Pitelka2>Pitelka, F. A., Tomich, P. Q. & Treichel, G.W. (1955). ''Ecological relations of jeagers and owls as Lemming predators near Barrow, Alaska''. Ecological Monographs 25: 85–117.</ref> Congregations were also recorded in the winter in Montana, where 31–35 owls wintered in a {{convert|2.6|km2|sqmi|abbr=on}} area, owls mostly grouped in loose aggregations of 5–10 owls each or occasionally side-by-side or about {{convert|20|m|ft|abbr=on}} apart.<ref name= Holt2>Holt, D. W. & Zetterberg, S. A. (2008). ''The 2005 to 2006 Snowy Owl irruption migration to western Montana''. Northwestern Naturalist 89 (3):145–151.</ref> In extreme cases in Utqiaġvik, the owls may have exceptionally close active nests that may be down to only {{convert|800|to|1600|m|ft|abbr=on}} apart.<ref name= Pitelka/> Juvenile males appear to be especially prone to loose associations with one another, appearing to be non-territorial and able to hunt freely in front of one another.<ref name= Holt/> In a {{convert|213|km2|sqmi|abbr=on}} area in and around Utqiaġvik, productive years may have about 54 nests while none may be found in poor years.<ref name= Holt/> Utqiaġvik may have about 5 owls in early summer every {{convert|1.6|km|mi|abbr=on}}, have a nest spacing of {{convert|1.6|to|3.2|km|mi|abbr=on}} and the owls territory size is about {{convert|5.2|to|10.2|km2|sqmi|abbr=on}}.<ref name= Holt/> In [[Churchill, Manitoba]], nest spacing averaged about {{convert|3.2|km|mi|abbr=on}}.<ref name= Shelford>Shelford, V. E. (1943). ''The abundance of the Collared Lemming (Dicrostonyx groenlandicus (TR) VAR. Richardsoni Mer.) in the Churchill area, 1929 to 1940''. Ecology 24 (4):472–484.</ref> In [[Southampton Island]] in a year when the owls nested there, nest spacing averaged {{convert|3.5|km|mi|abbr=on}}, with the closest two {{convert|1|km|mi|abbr=on}} apart and density per nest was {{convert|22|km2|sqmi|abbr=on}}.<ref>Parker, G. R. (1974). ''A population peak and crash of lemmings and Snowy Owls on Southampton Island, Northwest Territories''. Canadian Field-Naturalist. 88(2): 151–156.</ref> In Nunavut, densities could go from 1 owl per {{convert|2.6|km2|sqmi|abbr=on}} in a productive year to 1 owl per {{convert|26|km2|sqmi|abbr=on}} in a poor year and from 36 nests in a {{convert|100|km2|sqmi|abbr=on}} area to none at all.<ref name= Manning>Manning, T. H., Höhn, E. O. & MacPherson, A. H. (1956). ''The birds of Banks Island''. National Museum of Canada Bulletin 143, Biological Series 48.</ref><ref>Vaughn, R. (1992). ''In search of Arctic birds''. London: T & AD Poyser, Ltd.</ref> Owl density on Wrangel Island in Russia was observed be a single bird each {{convert|0.11|to|0.72|km2|sqmi|abbr=on}}.<ref name= Menyushina>Menyushina, I. E. (1997). ''Snowy Owl (Nyctea scandiaca) reproduction in relation to lemming population cycles on Wrangel Island''. In: ''Biology and conservation of owls of the Northern Hemisphere: 2nd International Symposium'', edited by J. R. Duncan, D. H. Johnson and T. H. Nicholls, 572–582. St. Paul: U.S. Dept. of Agriculture, Forest Service, North Central Forest Experiment Station.</ref> The first known study of winter territories took place in [[Horicon Marsh]] where owls ranged from {{convert|0.5|to|2.6|km2|sqmi|abbr=on}} each.<ref name= Keith/> In [[Calgary, Alberta]], mean territory size of juvenile females in winter was {{convert|407.5|ha|acre|abbr=on}} and adult females was {{convert|195.2|ha|acre|abbr=on}}.<ref name= Boxall/> Wintering owls in central Saskatchewan were radio-monitored, determining that 11 males had an average range of {{convert|54.4|km2|sqmi|abbr=on}}, while that of 12 females was {{convert|31.9|km2|sqmi|abbr=on}} with the combined average being {{convert|53.8|km2|sqmi|abbr=on}}.<ref>Chang, A. M., & Wiebe, K. L. (2018). ''Movement patterns and home ranges of male and female Snowy Owls (Bubo scandiacus) wintering on the Canadian prairies''. Canadian Journal of Zoology, 96(6), 545–552.</ref> @@ -89,12 +89,12 @@ ===Migration=== -It is fair to say that the snowy owl is a partial, if fairly irregular, [[Bird migration|migrant]], having a very broad but patchy wintering range.<ref name= Konig/> 1st year birds tend to disperse farther south in winter than older owls with males wintering usually somewhat more to the south than females of equivalent ages, adult females often wintering the farthest north.<ref name= Voous/><ref name= Scandinavica>Kerlinger, P. & Lein, M.R. (1986). ''Differences in winter range among age-sex classes of Snowy Owls Nyctea scandiaca in North America''. Ornis Scandinavica. 17(1): 1–17.</ref> The snowy owl likely covers more ground than almost any other owl in movements but many complex individual variations are known in movements, and they often do not take the traditional north–south direction that might be assumed.<ref name= Holt/> Migratory movements appear to be somewhat more common in America than in Asia.<ref name= Konig/> A study of wintering owls in the [[Kola Peninsula]] determined that the mean date of arrival of owls was 10 November with a departure date of 13 April, covering an average of {{convert|991|km|mi|abbr=on}} during the course of the wintering period and clustering where [[Ptarmigan|prey]] was more concentrated.<ref>Øien, I. J., Aarvak, T., Jacobsen, K. O., & Solheim, R. (2018). ''Satellite Telemetry Uncovers Important Wintering Areas for Snowy Owls On the Kola Peninsula, Northwestern Russia''. Орнитология, 42, 42–49.</ref> Some variety of movements recorded each autumn and snowy owls winter annually in plains of [[Siberia]] and Mongolia and [[prairie]]s and [[marsh]]lands of Canada.<ref name= Voous/> The [[Great Plains]] area of southern Canada host wintering snowy owls about 2 to 10 times more frequently than other areas of the continent.<ref name= Holt/> Some weak correlation has made with individuals having some level of fealty to certain wintering sites.<ref>Oeming, A. F. (1957). ''Notes on the Barred Owl and the Snowy Owl in Alberta''. Blue Jay 15:153–156.</ref><ref>Follen, D. & Luepke, K. (1980). ''Snowy Owl recaptures''. Inland Bird Banding 52: 60.</ref> Wintering snowy owls, a total of 419, recorded in [[Duluth, Minnesota]] from 1974 to 2012 would occur in larger numbers in years where [[Brown rat|rats]] were more plentiful. The amount of individual returns among 43 Duluth-wintering owls was fairly low in subsequent winters (8 for 1 year, a small handful in the next few years, and 9 in non-consecutive years).<ref name= Holt/> Sometimes surveys appeared to reveal hundreds of wintering snowy owls on coastal sea ice during an irruptive year.<ref name= Voous/><ref name= Marine/> Three siblings that hatched in same nest in [[Cambridge Bay]] were recovered in drastically different spots at least a year later: one in eastern [[Ontario]], one in [[Hudson Bay]] and one in [[Sakhalin Island]].<ref name= Parmelee/> A nestling banded in [[Sogn og Fjordane|Hordaland]] was recovered {{convert|1380|km|mi|abbr=on}} to the northeast in [[Finnmark]].<ref name= Voous/> In the [[Logan Airport]], 17 of 452 owls were recorded to return, eleven the following year, three 2 years later, and then singles variously 6, 10 and 16 years later.<ref name= Holt/> A banded female from Utqiaġvik was recorded to migrate over {{convert|1928|km|mi|abbr=on}} along seacoast down to Russia, returning over {{convert|1528|km|mi|abbr=on}} and covering at least {{convert|3476|km|mi|abbr=on}} in total. Another banded young female from Utqiaġvik went to the same Russian areas, returned to Utqiaġvik and then onto [[Victoria Island (Canada)|Victoria Island]], but did appear to breed, while another also covered a similar route but ended up nesting on [[Banks Island]]. Another female migrated to the [[Canada–United States border]], then moved back to the [[Gulf of Alaska]], then to winter in the same border areas and then finally to both Banks and Victoria Island.<ref name= Holt/><ref name= Fuller/> Snowy owls from the Canadian Arctic were monitored to have covered an average of {{convert|1100|km|mi|abbr=on}} in one autumn then covered an average of {{convert|2900|km|mi|abbr=on}} a year later.<ref name= Therrien2>Therrien, J.-F., Fitzgerald, G., Gauthier G. & Bêty, J. (2011). ''Diet-tissue discrimination factors of carbon and nitrogen stable isotopes in blood of Snowy Owl (Bubo scandiacus)''. Canadian Journal of Zoology 89 (4): 343–347.</ref> In late winter, owls from the same area were found to have covered a mean of {{convert|4093|km|mi|abbr=on}} of ground in the tundra and spent a mean of 108 days, apparently searching for a suitable nesting situation the entire time.<ref>Therrien, J.-F. , Gauthier, G., Pinaud, D. & Bêty, J. (2014). ''Irruptive movements and breeding dispersal of Snowy Owls: a specialized predator exploiting a pulsed resource''. Journal of Avian Biology. 45(6): 536–544.</ref> +It is fair to say that the snowy owl is a partial, if fairly irregular, [[Bird migration|migrant]], having a very broad but patchy wintering range.<ref name= Konig/> 1st year birds tend to disperse farther south in winter than older owls with males wintering usually somewhat more to the south than females of equivalent ages, adult females often wintering the farthest north.<ref name= Voous/><ref name= Scandinavica>Kerlinger, P. & Lein, M.R. (1986). ''Differences in winter range among age-sex classes of Snowy Owls Nyctea scandiaca in North America''. Ornis Scandinavica. 17(1): 1–17.</ref> The snowy owl likely covers more ground than almost any other owl in movements but many complex individual variations are known in movements, and they often do not take the traditional north–south direction that might be assumed.<ref name= Holt/> Migratory movements appear to be somewhat more common in America than in Asia.<ref name= Konig/> A study of wintering owls in the [[Kola Peninsula]] determined that the mean date of arrival of owls was 10 November with a departure date of 13 April, covering an average of {{convert|991|km|mi|abbr=on}} during the course of the wintering period and clustering where [[Ptarmigan|prey]] was more concentrated.<ref>Øien, I. J., Aarvak, T., Jacobsen, K. O., & Solheim, R. (2018). ''Satellite Telemetry Uncovers Important Wintering Areas for Snowy Owls On the Kola Peninsula, Northwestern Russia''. Орнитология, 42, 42–49.</ref> Some variety of movements recorded each autumn and snowy owls winter annually in plains of [[Siberia]] and Mongolia and [[prairie]]s and [[marsh]]lands of Canada.<ref name= Voous/> The [[Great Plains]] area of southern Canada host wintering snowy owls about 2 to 10 times more frequently than other areas of the continent.<ref name= Holt/> Some weak correlation has made with individuals having some level of fealty to certain wintering sites.<ref>Oeming, A. F. (1957). ''Notes on the Barred Owl and the Snowy Owl in Alberta''. Blue Jay 15:153–156.</ref><ref>Follen, D. & Luepke, K. (1980). ''Snowy Owl recaptures''. Inland Bird Banding 52: 60.</ref> Wintering snowy owls, a total of 419, recorded in [[Duluth, Minnesota]] from 1974 to 2012 would occur in larger numbers in years where [[Brown rat|rats]] were more plentiful. The amount of individual returns among 43 Duluth-wintering owls was fairly low in subsequent winters (8 for 1 year, a small handful in the next few years, and 9 in non-consecutive years).<ref name= Holt/> Sometimes surveys appeared to reveal hundreds of wintering snowy owls on coastal sea ice during an irruptive year.<ref name= Voous/><ref name= Marine/> Three siblings that hatched in same nest in [[Cambridge Bay]] were recovered in drastically different spots at least a year later: one in eastern [[Ontario]], one in [[Hudson Bay]] and one in [[Sakhalin Island]].<ref name= Parmelee/> A nestling banded in [[Sogn og Fjordane|Hordaland]] was recovered {{convert|1380|km|mi|abbr=on}} to the northeast in [[Finnmark]].<ref name= Voous/> In the [[Logan Airport]], 17 of 452 owls were recorded to return, eleven the following year, three 2 years later, and then singles variously 6, 10 and 16 years later.<ref name= Holt/> A banded female from Utqiaġvik was recorded to migrate over {{convert|1928|km|mi|abbr=on}} along seacoast down to Russia, returning over {{convert|1528|km|mi|abbr=on}} and covering at least {{convert|3476|km|mi|abbr=on}} in total. Another banded young female from Utqiaġvik went to the same Russian areas, returned to Utqiaġvik and then onto [[Victoria Island (Canada)|Victoria Island]], but did appear to breed, while another also covered a similar route but ended up nesting on [[Banks Island]]. Another female migrated to the [[Canada–United States border]], then moved back to the [[Gulf of Alaska]], then to winter in the same border areas and then finally to both Banks and Victoria Island.<ref name= Holt/> Snowy owls from the Canadian Arctic were monitored to have covered an average of {{convert|1100|km|mi|abbr=on}} in one autumn then covered an average of {{convert|2900|km|mi|abbr=on}} a year later.<ref name= Therrien2>Therrien, J.-F., Fitzgerald, G., Gauthier G. & Bêty, J. (2011). ''Diet-tissue discrimination factors of carbon and nitrogen stable isotopes in blood of Snowy Owl (Bubo scandiacus)''. Canadian Journal of Zoology 89 (4): 343–347.</ref> In late winter, owls from the same area were found to have covered a mean of {{convert|4093|km|mi|abbr=on}} of ground in the tundra and spent a mean of 108 days, apparently searching for a suitable nesting situation the entire time.<ref>Therrien, J.-F. , Gauthier, G., Pinaud, D. & Bêty, J. (2014). ''Irruptive movements and breeding dispersal of Snowy Owls: a specialized predator exploiting a pulsed resource''. Journal of Avian Biology. 45(6): 536–544.</ref> -In no fewer than 24 winters between 1882 and 1988, large numbers have occurred in Canada and the United States. These were [[Irruptive growth|irruption]] years.<ref name= Voous/> Record breeding irruptive years were recorded in the winters of 2011–2012 and 2014–2015.<ref name= Holt/><ref>Jorgensen, J. G., Dinan, L. R., & Walker Jr, T. J. (2012). ''Snowy Owl Invasion of 2011–12''.</ref> In the 1940s, it was calculated that the mean gape in time between large irruptions was 3.9 years.<ref name= Gross1/> Southbound movements as such are much more conspicuous after peak vole years, once thought to be separated by periods of around 3–7 years.<ref name= Voous/><ref>Snyder, L. L. (1943). ''The Snowy Owl migration of 1941–42''. Wilson Bulletin 55 (1):8–10.</ref><ref>Shelford, V. E. (1945). ''The relation of Snowy Owl migration to the abundance of the Collared Lemming''. Auk 62 (4):592–596.</ref><ref>Chitty, H. (1950). ''Canadian Arctic wild life enquiry, 1943–1949: With a summary of results since 1933''. Journal of Animal Ecology 19 (2):180–193.</ref><ref name="Godfrey" /> However, more extensive research has weakened the argument that irruptions are entirely food-based and the data indicates that irruptive movements are far from predictable. This is because a statewide survey in Alaska found no statewide synchrony in lemming numbers. Therefore, rather than decline of lemmings, it is the successful productivity of several pairs that plays the role, resulting in a large number of young owls that then irrupt. However, the snowy owls cannot breed in high numbers unless lemmings are widely available on the tundra.<ref name= Holt/><ref name= Kerlinger2/><ref name= Gross/><ref>Pitelka, F. A. & Batzli, G. O. (1993). ''Distribution, abundance, and habitat use by lemmings on the north slope of Alaska''. In: ''The biology of lemmings'', edited by N. C. Stenseth and R. A. Ims, 213–236. London: Academic Press.</ref><ref name="Krebs">Krebs, C. J. (1993). ''Are lemmings large Microtus or small reindeer? A review of lemming cycles after 25 years and future recommendations for future work''. In: ''The biology of lemmings'', edited by N. C. Stenseth and R. Ims, 247–260. London: Academic Press for the Linnean Society of London.</ref> This connection of irruptions to high years of productivity was confirmed in a study by Robillard et al. (2016).<ref>Robillard, A., Therrien, J. F., Gauthier, G., Clark, K. M., & Bêty, J. (2016). ''Pulsed resources at tundra breeding sites affect winter irruptions at temperate latitudes of a top predator, the snowy owl''. Oecologia, 181(2), 423–433.</ref> About 90% of the snowy owls seen in irruptive years from 1991 to 2016 that were ageable were identified as juveniles.<ref name= Santonja/> +In no fewer than 24 winters between 1882 and 1988, large numbers have occurred in Canada and the United States. These were [[Irruptive growth|irruption]] years.<ref name= Voous/> Record breeding irruptive years were recorded in the winters of 2011–2012 and 2014–2015.<ref name= Holt/> In the 1940s, it was calculated that the mean gape in time between large irruptions was 3.9 years.<ref name= Gross1/> Southbound movements as such are much more conspicuous after peak vole years, once thought to be separated by periods of around 3–7 years.<ref name= Voous/><ref>{{cite journal|author=Snyder, L. L. |year=1943|title=The Snowy Owl migration of 1941–42|journal= Wilson Bulletin |volume=55 |issue=1|pages=8–10|jstor=4157203|url=https://sora.unm.edu/sites/default/files/journals/wilson/v055n01/p0008-p0010.pdf}}</ref><ref>{{cite journal|doi=10.2307/4079810}}</ref><ref name=chitty/> However, more extensive research has weakened the argument that irruptions are entirely food-based and the data indicates that irruptive movements are far from predictable. This is because a statewide survey in Alaska found no statewide synchrony in lemming numbers. Therefore, rather than decline of lemmings, it is the successful productivity of several pairs that plays the role, resulting in a large number of young owls that then irrupt. However, the snowy owls cannot breed in high numbers unless lemmings are widely available on the tundra.<ref name= Holt/><ref name= Kerlinger2/><ref name= Gross/><ref>Pitelka, F. A. & Batzli, G. O. (1993). ''Distribution, abundance, and habitat use by lemmings on the north slope of Alaska''. In: ''The biology of lemmings'', edited by N. C. Stenseth and R. A. Ims, 213–236. London: Academic Press.</ref><ref name="Krebs">Krebs, C. J. (1993). ''Are lemmings large Microtus or small reindeer? A review of lemming cycles after 25 years and future recommendations for future work''. In: ''The biology of lemmings'', edited by N. C. Stenseth and R. Ims, 247–260. London: Academic Press for the Linnean Society of London.</ref> This connection of irruptions to high years of productivity was confirmed in a study by Robillard et al. (2016).<ref>{{cite journal|pmid=26920901|doi=10.1007/s00442-016-3588-3}}</ref> About 90% of the snowy owls seen in irruptive years from 1991 to 2016 that were ageable were identified as juveniles.<ref name= Santonja/> ==Feeding== ===Hunting techniques=== [[File:Harfang en vol 1.jpg|thumb|right|A snowy owl engaging in the "sweep" hunting method.]] -Snowy owls may hunt at nearly at any time of the day or night, but may not attempt to do so during particularly severe weather.<ref name= Holt/> During the [[summer solstice]], the owls appear to hunt during "theoretical nightfall".<ref name= Holt/> [[Night-vision device]]s have allowed biologists to observe that snowy owls hunt quite often during the extended nighttime during the northern winter.<ref name= Potapov/><ref name= Holt/><ref name="Manniche" /> Prey are both taken and eaten on the ground.<ref name= Konig/> Snowy owls, like other carnivorous birds, often swallow their small prey whole.<ref name= Konig/> Strong stomach juices digest the flesh, while the indigestible bones, teeth, fur, and feathers are compacted into oval pellets that the bird regurgitates 18 to 24 hours after feeding. Regurgitation often takes place at regular perches, where dozens of pellets may be found. Biologists frequently examine these pellets to determine the quantity and types of prey the birds have eaten. When large prey are eaten in small pieces, pellets will not be produced.<ref>[http://www.owlpages.com/owls.php?genus=Bubo&species=scandiacus Snowy Owl — ''Bubo scandiacus'', formerly ''Nyctea scandiaca'']. owlpages.com</ref> Larger prey is often torn apart, sometimes include removal of the head, with the large muscles, such as the [[humerus]] or [[Thorax|breast]], typically eaten first.<ref name= Holt/> The scattering of remains that results from the increment feeding on larger prey is thought to result in under-identification of them compared to smaller prey items.<ref>{{cite journal|title=A taphonomic investigation of small vertebrate accumulations produced by the snowy owl (''Bubo scandiacus'') and its implications for fossil studies|doi=10.1016/j.palaeo.2018.10.018}}</ref> The aptitude for hunting by day, hunting from the ground and hunting in almost always completely open and treeless areas are the primary ways in which the snowy owl differs in hunting from other ''Bubo'' owls. Otherwise, the hunting habits are similar.<ref name= Holt/><ref name= Johnsgard>[[Paul Johnsgard|Johnsgard, P. A.]] (1988). [https://digitalcommons.unl.edu/johnsgard/46/ ''North American owls: biology and natural history'']. Smithsonian Institution.</ref> It is thought, due to their less refined hearing compared to other owls, prey is usually perceived via vision and movement.<ref name= Voous/><ref name= Holt/> Experiments indicate that snowy owls can detect prey from as far as {{convert|1.6|km|mi|abbr=on}} away.<ref name= Smith/> Snowy owls generally use a rise or, occasionally, a perch while hunting.<ref name= Konig/> 88% of observed 34 hunts in Utqiaġvik were undertaken from an elevated watch-site (56% mounds or rises, 37% [[telephone pole]]s).<ref name= Holt/> Their hunting style may recall that of [[Buteo|buzzard]]s, with the hunting owl sitting rather low and perching immobile for a long spell.<ref name= Hume/> Although their usual flight is a slow, deliberate downbeat on the broad, fingered wings, when prey is detected from their perch, flight may undertaken with a sudden, surprisingly quick accelerated style with interspersed wing beats.<ref name= Hume/><ref>{{cite journal|author=Hohn, E. O. |year=1973|title=Winter hunting of Snowy Owls in farmland|journal= Canadian Field-Naturalist|volume= 87 |issue=4|pages= 468–469}}</ref> In Utqiaġvik, snowy owls may most frequently engage in a brief pursuit hunting style.<ref name= Holt/> In high winds capable of keeping their bulk aloft, snowy owls may too engage in a brief [[Levitation|hovering]] flight before dropping onto prey.<ref name= Watson/> When hunting fish, apparently, some snowy owls will hover in a style reminiscent of the [[osprey]] (''Pandion haliaetus''), although in at least one other case a snowy owl was observed to capture fish by lying on its belly upon a rock by a fishing hole.<ref name= Audubon>Audubon, J. J. (1840). ''The Birds of America''. Dover Publications, Inc., New York, NY, USA.</ref> A dashing stoop or pounce down onto their prey, ending in a high-impact "wallop", is fairly commonly recorded.<ref name= Holt/><ref name= Hume/> Another common technique is the "sweep", wherein they fly by and grasp the prey while continuing to fly.<ref name= Holt/><ref>{{cite journal|author=Dancey, H.E. |year=1983|title=Winter foraging habits of a Snowy Owl|journal= Indiana Audubon Quarterly|volume= 61|issue=4|pages= 136–144}}</ref> In winter, snowy owls have been shown to be able to "snow plunge" to capture prey in the [[Subnivean climate|subnivean zone]], under at least {{convert|20|cm|in|abbr=on}} of snow.<ref name= Smith/> Perhaps least frequently, snowy owls may pursue their on foot, in doing so never taking wing.<ref name= Holt/> Snowy owls have been known to capture [[Bird migration|night-migrating]] [[passerine]]s and [[shorebird]]s, sometimes perhaps on the wing, as well as large and/or [[Bird of prey|potentially dangerous]] birds that were caught in air by snowy owls during daylight.<ref name= Holt/> On the wing pursuits against other various other carnivorous birds are sometimes undertaken as well to [[Kleptoparasitism|kleptoparasitize]] the prey caught by the other birds.<ref name= Holt/><ref>Duffy, D. C., Beehler B. & Haas, W. (1976). ''Snowy Owl steals prey from Marsh Hawk''. Auk 93 (4): 839–840.</ref> Few variations of hunting technique were observed in winter observations from [[Alberta]], almost all of the hunts being with the sit-and-wait method (also known as still-hunts). Adult females in Alberta had a considerably better hunting rate than juvenile females.<ref name= Boxall2>{{cite journal|doi=10.14430/arctic2326|title=Feeding ecology of Snowy Owls (''Nyctea scandiaca'') wintering in S. Alberta}}</ref> Much as in Alberta, in [[Syracuse, New York]], 90% of 51 hunts were still-hunting, with the sweep variant used after perch departure in 31% of hunts and the pounce method in 45% of hunts. The Syracuse-wintering owls used tall perches, a mixture of manmade objects and trees of around {{convert|6|m|ft|abbr=on}} high, in nearly 61% of hunts, while nearly 14% were from low perches (i.e. fence-posts, snow banks and scrap piles) about half as high as the tall perches and started from a ground position nearly 10% of the time.<ref name= Winter>Winter, R. E. (2016). ''Hunting Behaviors and Foraging Success of Winter Irruptive Snowy Owls in New York''. SUNY College of Environmental Science and Forestry, Thesis.</ref> In Sweden, males hunted from a perch more so than did females and adults both focused on significantly smaller prey (small [[mammal]]s) and may have had more success hunting than juvenile snowy owls.<ref name= Lind/> Some snowy owls can survive a fast for up to about 40 days off of [[Fatty acid metabolism|fat reserves]].<ref name= Hume/> These owls were found to have extremely thick [[Subcutaneous tissue|subcutaneous fat deposits]] of around {{convert|19|to|22|mm|in|abbr=on}} and it is likely owls that overwinter in the Arctic rely heavily on these to survive during this scarce time, in combination with lethargic, energy-conserving behavior. +Snowy owls may hunt at nearly at any time of the day or night, but may not attempt to do so during particularly severe weather.<ref name= Holt/> During the [[summer solstice]], the owls appear to hunt during "theoretical nightfall".<ref name= Holt/> [[Night-vision device]]s have allowed biologists to observe that snowy owls hunt quite often during the extended nighttime during the northern winter.<ref name= Potapov/><ref name= Holt/> Prey are both taken and eaten on the ground.<ref name= Konig/> Snowy owls, like other carnivorous birds, often swallow their small prey whole.<ref name= Konig/> Strong stomach juices digest the flesh, while the indigestible bones, teeth, fur, and feathers are compacted into oval pellets that the bird regurgitates 18 to 24 hours after feeding. Regurgitation often takes place at regular perches, where dozens of pellets may be found. Biologists frequently examine these pellets to determine the quantity and types of prey the birds have eaten. When large prey are eaten in small pieces, pellets will not be produced.<ref>[http://www.owlpages.com/owls.php?genus=Bubo&species=scandiacus Snowy Owl — ''Bubo scandiacus'', formerly ''Nyctea scandiaca'']. owlpages.com</ref> Larger prey is often torn apart, sometimes include removal of the head, with the large muscles, such as the [[humerus]] or [[Thorax|breast]], typically eaten first.<ref name= Holt/> The scattering of remains that results from the increment feeding on larger prey is thought to result in under-identification of them compared to smaller prey items.<ref>{{cite journal|title=A taphonomic investigation of small vertebrate accumulations produced by the snowy owl (''Bubo scandiacus'') and its implications for fossil studies|doi=10.1016/j.palaeo.2018.10.018}}</ref> The aptitude for hunting by day, hunting from the ground and hunting in almost always completely open and treeless areas are the primary ways in which the snowy owl differs in hunting from other ''Bubo'' owls. Otherwise, the hunting habits are similar.<ref name= Holt/><ref name= Johnsgard>[[Paul Johnsgard|Johnsgard, P. A.]] (1988). [https://digitalcommons.unl.edu/johnsgard/46/ ''North American owls: biology and natural history'']. Smithsonian Institution.</ref> It is thought, due to their less refined hearing compared to other owls, prey is usually perceived via vision and movement.<ref name= Voous/><ref name= Holt/> Experiments indicate that snowy owls can detect prey from as far as {{convert|1.6|km|mi|abbr=on}} away. Snowy owls generally use a rise or, occasionally, a perch while hunting.<ref name= Konig/> 88% of observed 34 hunts in Utqiaġvik were undertaken from an elevated watch-site (56% mounds or rises, 37% [[telephone pole]]s).<ref name= Holt/> Their hunting style may recall that of [[Buteo|buzzard]]s, with the hunting owl sitting rather low and perching immobile for a long spell.<ref name= Hume/> Although their usual flight is a slow, deliberate downbeat on the broad, fingered wings, when prey is detected from their perch, flight may undertaken with a sudden, surprisingly quick accelerated style with interspersed wing beats.<ref name= Hume/><ref>{{cite journal|author=Hohn, E. O. |year=1973|title=Winter hunting of Snowy Owls in farmland|journal= Canadian Field-Naturalist|volume= 87 |issue=4|pages= 468–469}}</ref> In Utqiaġvik, snowy owls may most frequently engage in a brief pursuit hunting style.<ref name= Holt/> In high winds capable of keeping their bulk aloft, snowy owls may too engage in a brief [[Levitation|hovering]] flight before dropping onto prey.<ref name= Watson/> When hunting fish, apparently, some snowy owls will hover in a style reminiscent of the [[osprey]] (''Pandion haliaetus''), although in at least one other case a snowy owl was observed to capture fish by lying on its belly upon a rock by a fishing hole.<ref name= Audubon>Audubon, J. J. (1840). ''The Birds of America''. Dover Publications, Inc., New York, NY, USA.</ref> A dashing stoop or pounce down onto their prey, ending in a high-impact "wallop", is fairly commonly recorded.<ref name= Holt/><ref name= Hume/> Another common technique is the "sweep", wherein they fly by and grasp the prey while continuing to fly.<ref name= Holt/><ref>{{cite journal|author=Dancey, H.E. |year=1983|title=Winter foraging habits of a Snowy Owl|journal= Indiana Audubon Quarterly|volume= 61|issue=4|pages= 136–144}}</ref> In winter, snowy owls have been shown to be able to "snow plunge" to capture prey in the [[Subnivean climate|subnivean zone]], under at least {{convert|20|cm|in|abbr=on}} of snow. Perhaps least frequently, snowy owls may pursue their on foot, in doing so never taking wing.<ref name= Holt/> Snowy owls have been known to capture [[Bird migration|night-migrating]] [[passerine]]s and [[shorebird]]s, sometimes perhaps on the wing, as well as large and/or [[Bird of prey|potentially dangerous]] birds that were caught in air by snowy owls during daylight.<ref name= Holt/> On the wing pursuits against other various other carnivorous birds are sometimes undertaken as well to [[Kleptoparasitism|kleptoparasitize]] the prey caught by the other birds.<ref name= Holt/><ref>Duffy, D. C., Beehler B. & Haas, W. (1976). ''Snowy Owl steals prey from Marsh Hawk''. Auk 93 (4): 839–840.</ref> Few variations of hunting technique were observed in winter observations from [[Alberta]], almost all of the hunts being with the sit-and-wait method (also known as still-hunts). Adult females in Alberta had a considerably better hunting rate than juvenile females.<ref name= Boxall2>{{cite journal|doi=10.14430/arctic2326|title=Feeding ecology of Snowy Owls (''Nyctea scandiaca'') wintering in S. Alberta}}</ref> Much as in Alberta, in [[Syracuse, New York]], 90% of 51 hunts were still-hunting, with the sweep variant used after perch departure in 31% of hunts and the pounce method in 45% of hunts. The Syracuse-wintering owls used tall perches, a mixture of manmade objects and trees of around {{convert|6|m|ft|abbr=on}} high, in nearly 61% of hunts, while nearly 14% were from low perches (i.e. fence-posts, snow banks and scrap piles) about half as high as the tall perches and started from a ground position nearly 10% of the time.<ref name= Winter>Winter, R. E. (2016). ''Hunting Behaviors and Foraging Success of Winter Irruptive Snowy Owls in New York''. SUNY College of Environmental Science and Forestry, Thesis.</ref> In Sweden, males hunted from a perch more so than did females and adults both focused on significantly smaller prey (small [[mammal]]s) and may have had more success hunting than juvenile snowy owls.<ref name= Lind/> Some snowy owls can survive a fast for up to about 40 days off of [[Fatty acid metabolism|fat reserves]].<ref name= Hume/> These owls were found to have extremely thick [[Subcutaneous tissue|subcutaneous fat deposits]] of around {{convert|19|to|22|mm|in|abbr=on}} and it is likely owls that overwinter in the Arctic rely heavily on these to survive during this scarce time, in combination with lethargic, energy-conserving behavior. Snowy owls may not infrequently exploit prey inadvertently provided or compromised by human activities, including ducks injured by [[Hunting|duck hunters]], [[Red phalarope|birds]] maimed by [[Antenna (radio)|antenna]] wires, various animals caught in human [[Trapping|traps]] and [[trapline]]s as well as [[Domestication of animals|domestic]] or wild prey being bred or farmed by humans in enclosures.<ref name= Watson/><ref name=Wiggins/><ref>Brooks, W. S. (1915). ''Notes on birds from east Siberia and Arctic Alaska''. Bulletin of the Museum of Comparative Zoology 59:361–413.</ref><ref>Nagell, B. & Frycklund, I. (1965). ''The irruption of the Snowy Owl (Nyctea scandiaca) in Scandinavia in the winters of 1960–1963 and notes on its behavior''. Vår Fågelvärld 24 (1): 26–55.</ref><ref>King, B., Nayler, F. & Wardle, F. (1966). ''Feeding and resting behavior of a Snowy Owl in Scilly''. British Birds 59 (3): 108.</ref><ref name= Robertson>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/jrr/v037n02/p00164-p00166.pdf|author1=Robertson, G. J. |author2=Gilchrist, H. G. |year=2003|title=Wintering Snowy Owls feed on sea ducks in the Belcher Islands, Nunavut, Canada|journal= Journal of Raptor Research |volume=37 |issue=2|pages= 164–166}}</ref> A wide variety of accrued reports show that the snowy owl that [[Scavenger|scavenging]] on [[carrion]] is not uncommon (despite having once been thought to be very rare in all owls), including instances of [[reindeer]] (''Rangifer tarandus'') body parts brought to nests and owls following [[polar bear]]s to secondarily feed on their kills. Even huge [[marine mammal]]s such as [[walrus]] (''Odobenus rosmarus'') and whales can be fed upon by these owls when the opportunity occurs.<ref name= Holt/><ref>{{cite journal|doi=10.3356/0892-1016-53.4.410}}</ref> Snowy owls produce a [[Pellet (ornithology)|pellet]] that in different areas averages a median of about {{convert|80|x|30|mm|in|abbr=on}}, averaging up to {{convert|92|mm|in|abbr=on}} in length as in Europe.<ref name= Cramp/><ref name= Detienne/><ref name= Patterson/><ref name= Hagen/> @@ -120,5 +120,5 @@ On the isle of [[St. Kilda, Scotland|St. Kilda]], 24 pellets were found for non-breeding snowy owls that stayed through the early summer. Of 46 prey items, the [[St Kilda field mouse]] (''Apodemus sylvaticus hirtensis'') was predominant by number at 69.6% but constituted 16.8% of biomass while adult [[Atlantic puffin]] (''Fratercula arctica'') constituted 63.5% of the prey biomass and 26% by number (rest of the balance being juvenile puffins and [[great skua]]s (''Stercorarius skua'')).<ref name= Miles>Miles, W. T. S., & Money, S. (2008). ''Behaviour and diet of non-breeding Snowy Owls on St Kilda''. Scottish Birds, 28, 11.</ref> The main subspecies of [[wood mouse]] was similarly dominant in the diet within [[County Mayo]], Ireland and were presumably snatched at night due to their strict [[nocturnality]].<ref>{{cite journal|author1=Murrey, T. |author2= Sleeman, D. |year=2005|title=Dietary analysis from the Snowy Owls pellets ''Nyctea scandiaca'' Linnaeus 1958, from the Mullet Peninsula, Co, Mayo|journal= Irish Naturalists' Journal|volume= 283|pages= 136}}</ref> In [[Knockando, Moray|Knockando]], the winter diet was led by [[European rabbit]]s (40.1%), [[red grouse]] (''Lagopus lagopus scotica'') (26.4%) and adult [[mountain hare]] (''Lepus timidus'') (20.9%) (in 156 pellets); in [[Ben Macdui]], the diet was led by rock ptarmigan (72.3%), [[field vole]]s (''Microtus agrestis'') and juvenile mountain hare (8.5%) (33 pellets); in [[Cabrach]], the diet was led by red grouse (40%), mountain hare (20%) and European rabbit (15%) (16 pellets).<ref name= Savory>{{cite journal|url=https://www.researchgate.net/publication/336837560_Unpublished_information_in_the_SOC_Archive_on_Snowy_Owl_diet_at_three_locations_in_Moray_in_the_1960s_Unpublished_information_in_the_SOC_Archive_on_Snowy_Owl_diet_at_three_locations_in_Moray_in_the_19|author=Savory, J. |year=2019|title=Unpublished information in the SOC Archive on Snowy Owl diet at three locations in Moray in the 1960s|journal= Scottish Birds|volume= 202|issue=204|pages= 202}}</ref> Among 110 prey items found for snowy owls found wintering during irruption in southern Finland, all but 1 prey item were field voles (the only other prey being a single [[long-tailed duck]] (''Clangula hyemalis'')).<ref name= Hakala/> Far to the east, wintering owls in the [[Irkutsky District]] were found to subsist mostly on [[narrow-headed vole]]s (''Microtus gregalis'').<ref name= Maleev>Maleev, V.G. & Popov, V. V. (2007). ''Birds of forest-steppes of the Upper Angara river basin''. Irkutsk.</ref> In a wintering population in Kurgaldga Nature Reserve of Kazakhstan, the main foods were [[grey red-backed vole]]s at 47.4%, [[winter white dwarf hamster]] (''Phodopus sungorus'') at 18.4%, [[steppe pika]] (''Ochotona pusilla'') at 7.9%, muskrat at 7.9%, [[Eurasian skylark]] (''Alauda arvensis'') at 7.9%, [[grey partridge]] at 5.3%, and both [[steppe polecat]] (''Mustela eversmanii'') and [[yellowhammer]] (''Emberiza citrinella'') at 2.6%<ref>Mosalev, A. (1969). ''About wintering of Snowy Owl in the Kurgaldga Nature Reserve''.</ref> On the [[Kuril Islands]], wintering snowy owls main foods were reported as tundra voles, brown rats, ermines and whimbrel, in roughly that order.<ref name= Potapov/> -Data from the [[Logan Airport]] in over 6,000 pellets shows that meadow vole and brown rat predominated the diet in the area, supplanted by assorted birds both small and large.<ref name= Holt/><ref name= Smith/> [[American black duck]]s were primarily taken among bird species with other birds taken here including relatively large and diverse species [[Canada geese]] (''Branta canadensis''), brants, [[American herring gull]]s (''Larus argentatus''), [[double-crested cormorant]] (''Phalacrocorax auritus''), [[great blue heron]] (''Ardea herodias''), in addition to some formidable mammals such as [[Cat|house cat]], [[American mink]] (''Mustela vision''), and [[striped skunk]] (''Mephitis mephitis'').<ref name= Holt/><ref name= Smith/> Given the large size of some of this prey, it can be projected that the snowy owl can kill adult prey of around twice their own weight (i.e. geese, cats, skunks, etc.).<ref name= Holt/><ref name= Smith/> Other large prey is sometimes taken by snowy owls, all roughly within the {{convert|2|to|5|kg|lb|abbr=on}} weight range often include adults of large [[leporid]]s such as [[Arctic hare]] (''Lepus arcticus''),<ref name= Holt/> [[Alaskan hare]] (''Lepus othus''),<ref>Best, T. L., & Henry, T. H. (1994). ''Lepus othus''. Mammalian Species, (458), 1–5.</ref> [[mountain hare]]<ref>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V54/V54_N08/V54_N08_P307_320_A051.pdf|author=Bergman, G. |year=1961|title=The food of birds of prey and owls in Fenno-Scandia|journal= British Birds|volume= 54|issue=8|pages= 307–320}}</ref> and [[white-tailed jackrabbit]]s (''Lepus townsendii'').<ref name= Boxall2/> As well as several species of geese, probable cygnets of [[Tundra swan|Bewick's swan]]s (''Cygnus columbianus bewickii'')<ref>Nagy, S., Petkov, N., Rees, E., Solokha, A., Hilton, G., Beekman, J., & Nolet, B. (2012). [https://www.unep-aewa.org/en/publication/international-single-species-action-plan-conservation-northwest-european-population International single species action plan for the conservation of the northwest European population of Bewick's Swan (''Cygnus columbianus bewickii'')]. Wetlands International and The Wildfowl & Wetlands Trust (WWT), AEWA Technical Series, (44).</ref> as well as adults of the following: [[western capercaillie]] (''Tetrao urogallus'') (of both sexes),<ref>Gilyazov, A. V. (2005). ''Snowy Owl Nyctea scandiaca Linnaeus, 1758''. Red-data Book of the Murmansk Region. Murmansk: Murmansk book publishers: 316—318. [in Russian].</ref> [[greater sage-grouse]] (''Centrocercus urophasianus'')<ref>{{cite journal|doi=10.1002/jwmg.21168}}</ref> and [[yellow-billed loon]]s (''Gavia adamsii'').<ref>Uher-Koch, B. D., M. R. North, and J. A. Schmutz (2020). Yellow-billed Loon (''Gavia adamsii''), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.</ref> At the other end of the scale, the snowy owl has been known to take birds down to size of {{convert|19.5|g|oz|abbr=on}} [[dark-eyed junco]]s (''Junco hyemalis'') and mammals down the size of {{convert|8.1|g|oz|abbr=on}} [[common shrew]]s (''Sorex araneus'').<ref name= Hakala/><ref name= Young/><ref name= CRC1>Dunning, Jr., J. B. (1993). ''CRC handbook of avian body masses''. CRC Press, Boca Raton, FL.</ref> Fish are rarely taken anywhere but the snowy owl has been known to prey upon [[Arctic char]] (''Salvelinus alpinus'') and [[lake trout]] (''Salvelinus namaycush'').<ref name= Voous/><ref name= Gross/><ref name= Bailey>Bailey, A. M. (1948). ''Birds of Arctic Alaska''. Colorado Mus. Nat. Hist., Popular Ser., 8.</ref> +Data from the [[Logan Airport]] in over 6,000 pellets shows that meadow vole and brown rat predominated the diet in the area, supplanted by assorted birds both small and large.<ref name= Holt/> [[American black duck]]s were primarily taken among bird species with other birds taken here including relatively large and diverse species [[Canada geese]] (''Branta canadensis''), brants, [[American herring gull]]s (''Larus argentatus''), [[double-crested cormorant]] (''Phalacrocorax auritus''), [[great blue heron]] (''Ardea herodias''), in addition to some formidable mammals such as [[Cat|house cat]], [[American mink]] (''Mustela vision''), and [[striped skunk]] (''Mephitis mephitis'').<ref name= Holt/> Given the large size of some of this prey, it can be projected that the snowy owl can kill adult prey of around twice their own weight (i.e. geese, cats, skunks, etc.).<ref name= Holt/> Other large prey is sometimes taken by snowy owls, all roughly within the {{convert|2|to|5|kg|lb|abbr=on}} weight range often include adults of large [[leporid]]s such as [[Arctic hare]] (''Lepus arcticus''),<ref name= Holt/> [[Alaskan hare]] (''Lepus othus''),<ref>Best, T. L., & Henry, T. H. (1994). ''Lepus othus''. Mammalian Species, (458), 1–5.</ref> [[mountain hare]]<ref>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V54/V54_N08/V54_N08_P307_320_A051.pdf|author=Bergman, G. |year=1961|title=The food of birds of prey and owls in Fenno-Scandia|journal= British Birds|volume= 54|issue=8|pages= 307–320}}</ref> and [[white-tailed jackrabbit]]s (''Lepus townsendii'').<ref name= Boxall2/> As well as several species of geese, probable cygnets of [[Tundra swan|Bewick's swan]]s (''Cygnus columbianus bewickii'')<ref>Nagy, S., Petkov, N., Rees, E., Solokha, A., Hilton, G., Beekman, J., & Nolet, B. (2012). [https://www.unep-aewa.org/en/publication/international-single-species-action-plan-conservation-northwest-european-population International single species action plan for the conservation of the northwest European population of Bewick's Swan (''Cygnus columbianus bewickii'')]. Wetlands International and The Wildfowl & Wetlands Trust (WWT), AEWA Technical Series, (44).</ref> as well as adults of the following: [[western capercaillie]] (''Tetrao urogallus'') (of both sexes),<ref>Gilyazov, A. V. (2005). ''Snowy Owl Nyctea scandiaca Linnaeus, 1758''. Red-data Book of the Murmansk Region. Murmansk: Murmansk book publishers: 316—318. [in Russian].</ref> [[greater sage-grouse]] (''Centrocercus urophasianus'')<ref>{{cite journal|doi=10.1002/jwmg.21168}}</ref> and [[yellow-billed loon]]s (''Gavia adamsii'').<ref>Uher-Koch, B. D., M. R. North, and J. A. Schmutz (2020). Yellow-billed Loon (''Gavia adamsii''), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.</ref> At the other end of the scale, the snowy owl has been known to take birds down to size of {{convert|19.5|g|oz|abbr=on}} [[dark-eyed junco]]s (''Junco hyemalis'') and mammals down the size of {{convert|8.1|g|oz|abbr=on}} [[common shrew]]s (''Sorex araneus'').<ref name= Hakala/><ref name= Young/><ref name= CRC1>Dunning, Jr., J. B. (1993). ''CRC handbook of avian body masses''. CRC Press, Boca Raton, FL.</ref> Fish are rarely taken anywhere but the snowy owl has been known to prey upon [[Arctic char]] (''Salvelinus alpinus'') and [[lake trout]] (''Salvelinus namaycush'').<ref name= Voous/><ref name= Gross/><ref name= Bailey>Bailey, A. M. (1948). ''Birds of Arctic Alaska''. Colorado Mus. Nat. Hist., Popular Ser., 8.</ref> ===Interspecific predatory relationships=== @@ -126,16 +126,16 @@ The snowy owl is in many ways a very unique owl and differs from other species of owl in its [[ecological niche]].<ref name= Voous/><ref name= Johnsgard/> Only one other owl, the [[short-eared owl]], is known to breed in the High Arctic.<ref name= Voous/> However, the snowy owl shares its primary prey, the [[True lemming|brown]] and [[collared lemming]]s, with a number of other avian predators. In sometimes differing parts of the Arctic, competing predators for lemmings are, in addition to short-eared owls, [[pomarine jaeger]]s (''Stercorarius pomarinus''), [[long-tailed jaeger]]s (''Stercorarius longicaudus''), [[rough-legged buzzard]]s (''Buteo lagopus''), [[hen harrier]]s (''Circus cyaenus''), [[northern harrier]]s (''Circus hudsonius'') and generally less specialized [[gyrfalcon]]s (''Falco rusticollis''), [[peregrine falcon]]s (''Falco peregrinus''), [[glaucous gull]]s (''Larus hypoboreus'') and [[common raven]]s (''Corvus corax''). Certain carnivorous mammals, especially the [[Arctic fox]] and, in this region, the [[Stoat|ermine]], are also specialized to hunt lemmings.<ref name= Voous/><ref name= Pitelka/><ref>{{cite journal|doi=10.2307/3545963}}</ref><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v082n02/p0130-p0157.pdf|author=Maher, W. J. |year=1970|title=The Pomarine Jaeger as a Brown Lemming predator in northern Alaska|journal= Wilson Bulletin|volume= 82|pages= 130–157}}</ref> Most of the lemming predators are intolerant of the competition given the scattered nature of lemming populations and will displace and/or kill one another given the chance. However, given the need to conserve energy in the extreme environment, the predators may react passively to one another.<ref>{{cite journal|jstor=4314894|author=Wiklund, C. G., Angerbjörn, A., Isakson, E., Kjellén, N., & Tannerfeldt, M. |year=1999|title=Lemming predators on the Siberian tundra|journal=Ambio|volume= 281–286}}</ref><ref name="Gilg" /> When unusually breeding south in the Subarctic such as western Alaska, Scandinavia and central Russia, the number of predators with which the snowy owls are obligated to share prey and compete with may be too numerous to name.<ref name= Potapov/> The taking of the young and eggs of snowy owls has been committed by a large number of predators: [[Buteo|hawks]] and [[eagle]]s, the northern [[Skua|jaeger]]s, peregrine and gyrfalcons, glaucous gulls, common ravens, [[Arctic wolf|Arctic wolves]] (''Canis lupus arctos''), [[polar bear]]s, [[brown bear]]s (''Ursus arctos''), [[wolverine]]s (''Gulo gulo'') and perhaps especially the Arctic fox.<ref name= Holt/><ref name= Taylor/><ref>Ovsyanikov, N.G. & Menushina, I.E. (1986). ''[Competition for food between the Snowy Owl (Nyctea scandiaca) and the arctic fox (Alopex lagopus)]''. Zoologischeskii Zhurnal. 65(6): 901–910. In Russian with English summary.</ref> Adult snowy owls on the breeding grounds are far less vulnerable and can be justifiably qualified as an [[apex predator]].<ref name= Konig/><ref name= Voous/> Instances of killing of adult snowy owls on the breeding grounds have been witnessed to be committed by a pair of [[pomarine jaeger]]s on an incubating adult female snowy owl (possibly merely a competitive attack as she was left uneaten) and by an Arctic fox that killed an adult male snowy owl.<ref name= Bailey/><ref>Menyushina, I. E. (1994). "Interspecies relation of the polar fox (''Alopex lagopus'' L.) and the Snowy Owl (''Nyctea scandiaca'' L.) during the breeding season in the Wrangel Island. 1". Lutreola 3: 15–21.</ref> [[File:Die Raubvögel Deutschlands und des angrenzenden Mitteleuropas (Pl. L) (21138120888).jpg|thumb|An early illustration showing snowy owl predation upon a [[gyrfalcon]].]] -When it goes south to winter outside of the Arctic, the snowy owl has a potential to interact with a number of additional predators.<ref name= Voous/> By necessity, it shares its wintertime diverse prey with a number of formidable predators.<ref name= Voous/><ref name= Holt/> These are known to include their cousins, the [[great horned owl]] and the [[Eurasian eagle-owl]]. They are relieved of heavy competition from the related species by differing temporal activity, i.e. being more likely to actively hunt in daytime, and by habitat, using rather more open (quite often nearly treeless) habitats than them.<ref name= Potapov/><ref name= Voous/> During a study of wintering snowy owls in [[Saskatchewan]], the authors indicated that the snowy owls may avoid areas inhabited and defended by great horned owls. Although they usually occurred here outside of a {{convert|800|m|ft|abbr=on}} radius of central great horned owl ranges, they did not avoid the {{convert|1600|m|ft|abbr=on}} radius and different habitat usage may be a dictating factor.<ref name= Chang2>Chang, A. M. (2017). ''Habitat use, movement patterns, and body condition of male and female Snowy Owls (Bubo scandiacus) in winter'' (Doctoral dissertation, University of Saskatchewan).</ref> Given their mildly slighter size, it is unlikely that great horned owls (unlike the larger eagle-owl) would regularly dominate snowy owls in interactions and either species may give way to other depending on the size and disposition of the owls involved.<ref name= Potapov/><ref name= Voous/> Little study has been undertaken into the [[Trophic level|trophic competition]] of snowy owls with other predators during winter and, due to their scarcity, few predators are likely to expel much energy on competitive interactions with them, although many other predators will engage in anti-predator [[Mobbing (animal behavior)|mobbing]] of snowy owls.<ref name= Voous/><ref name= Holt/> Largely in winter, snowy owls have been the victim of a number of larger avian predators, though attacks are likely to be singular and rare.<ref name= Voous/><ref name= Holt/> Instances of predation on snowy owls are known to have been committed several times in winter only by [[Eurasian eagle-owl]]s.<ref name= Mikkola3>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V69/V69_N04/V69_N04_P144_154_A030.pdf|author=Mikkola, H. |year=1976|title=Owls killing and killed by other owls and raptors in Europe|journal= British Birds|volume= 69|pages= 144–154}}</ref> Additionally, [[golden eagle]]s (''Aquila chrysaetos'') have been known to prey on snowy owls as well as all northern [[sea eagle]]s: the [[Bald eagle|bald]] (''Haliaeetus leucocephalus''), [[White-tailed eagle|white-tailed]] (''Haliaeetus albicilla'') and [[Steller's sea eagle]]s (''Haliaeetus pelagicus'').<ref name= Holt/><ref name= Campbell/><ref>{{cite journal|author=Johnson, M.J. |year=1995|title=Bald Eagle predation on Snowy Owl|journal= Loon|volume= 67|issue=2|pages=107}}</ref> Snowy owls are also sometimes killed by birds that are mobbing them. In one instance, a [[peregrine falcon]] killed a snowy owl in a stoop after the owl had itself killed a fledgling falcon.<ref name= Bent/><ref name= Bailey/><ref>Nelson, E. W. (1887). ''Birds of Alaska'', p. 35-222. In H. W. Henshaw [ed.], Report upon natural history collections made in Alaska between the years 1877 and 188 1. No. III Arctic Series, Signal Service, U.S. Army, Government Printing Office,-Washington, DC.</ref> Anecdotal report indicate predation by [[gyrfalcon]]s (on snowy owls of unknown age and condition) but it was possibly also an act of mobbing.<ref name= Heggoy>Heggøy, O., & Øien, I. J. (2014). ''Conservation status of birds of prey and owls in Norway''. NOF/BirdLife Norway-Report, 1, 1–129.</ref> In another, a huge [[Flock (birds)|throng]] of [[Arctic tern]]s (''Sterna paradisaea'') relentlessly swarmed and attacked a snowy owl until it meet its demise.<ref>Meinertzhagen, R. (1959). ''Pirates and Predators: The piratical and predatory habits of birds''. Oliver & Boyd.</ref> +When it goes south to winter outside of the Arctic, the snowy owl has a potential to interact with a number of additional predators.<ref name= Voous/> By necessity, it shares its wintertime diverse prey with a number of formidable predators.<ref name= Voous/><ref name= Holt/> These are known to include their cousins, the [[great horned owl]] and the [[Eurasian eagle-owl]]. They are relieved of heavy competition from the related species by differing temporal activity, i.e. being more likely to actively hunt in daytime, and by habitat, using rather more open (quite often nearly treeless) habitats than them.<ref name= Potapov/><ref name= Voous/> During a study of wintering snowy owls in [[Saskatchewan]], the authors indicated that the snowy owls may avoid areas inhabited and defended by great horned owls. Although they usually occurred here outside of a {{convert|800|m|ft|abbr=on}} radius of central great horned owl ranges, they did not avoid the {{convert|1600|m|ft|abbr=on}} radius and different habitat usage may be a dictating factor.<ref name= Chang2>Chang, A. M. (2017). ''Habitat use, movement patterns, and body condition of male and female Snowy Owls (Bubo scandiacus) in winter'' (Doctoral dissertation, University of Saskatchewan).</ref> Given their mildly slighter size, it is unlikely that great horned owls (unlike the larger eagle-owl) would regularly dominate snowy owls in interactions and either species may give way to other depending on the size and disposition of the owls involved.<ref name= Potapov/><ref name= Voous/> Little study has been undertaken into the [[Trophic level|trophic competition]] of snowy owls with other predators during winter and, due to their scarcity, few predators are likely to expel much energy on competitive interactions with them, although many other predators will engage in anti-predator [[Mobbing (animal behavior)|mobbing]] of snowy owls.<ref name= Voous/><ref name= Holt/> Largely in winter, snowy owls have been the victim of a number of larger avian predators, though attacks are likely to be singular and rare.<ref name= Voous/><ref name= Holt/> Instances of predation on snowy owls are known to have been committed several times in winter only by [[Eurasian eagle-owl]]s.<ref name= Mikkola3>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V69/V69_N04/V69_N04_P144_154_A030.pdf|author=Mikkola, H. |year=1976|title=Owls killing and killed by other owls and raptors in Europe|journal= British Birds|volume= 69|pages= 144–154}}</ref> Additionally, [[golden eagle]]s (''Aquila chrysaetos'') have been known to prey on snowy owls as well as all northern [[sea eagle]]s: the [[Bald eagle|bald]] (''Haliaeetus leucocephalus''), [[White-tailed eagle|white-tailed]] (''Haliaeetus albicilla'') and [[Steller's sea eagle]]s (''Haliaeetus pelagicus'').<ref name= Holt/><ref name= Campbell/><ref>{{cite journal|author=Johnson, M.J. |year=1995|title=Bald Eagle predation on Snowy Owl|journal= Loon|volume= 67|issue=2|pages=107}}</ref> Snowy owls are also sometimes killed by birds that are mobbing them. In one instance, a [[peregrine falcon]] killed a snowy owl in a stoop after the owl had itself killed a fledgling falcon.<ref name= Bent/><ref name= Bailey/><ref>Nelson, E. W. (1887). ''Birds of Alaska'', p. 35-222. In H. W. Henshaw [ed.], Report upon natural history collections made in Alaska between the years 1877 and 188 1. No. III Arctic Series, Signal Service, U.S. Army, Government Printing Office,-Washington, DC.</ref> Anecdotal report indicate predation by [[gyrfalcon]]s (on snowy owls of unknown age and condition) but it was possibly also an act of mobbing.<ref name= Heggoy>Heggøy, O., & Øien, I. J. (2014). [https://www.birdlife.no/innhold/bilder/2014/01/29/2586/nof_rapport_12014.pdf ''Conservation status of birds of prey and owls in Norway'']. NOF/BirdLife Norway-Report, 1, 1–129.</ref> In another, a huge [[Flock (birds)|throng]] of [[Arctic tern]]s (''Sterna paradisaea'') relentlessly swarmed and attacked a snowy owl until it meet its demise.<ref>Meinertzhagen, R. (1959). ''Pirates and Predators: The piratical and predatory habits of birds''. Oliver & Boyd.</ref> -Almost certainly more often than being victim of other predators, snowy owls are known to dominate, kill and feed on a large diversity of other predators.<ref name= Voous/><ref name= Mikkola3/> Snowy owls, much like other ''Bubo'' owls, will opportunistically kill other birds of prey and predators. Although they will readily plunder the nests of other raptorial birds given the opportunity, most predations are on full-grown raptorial birds during winter due to the scarcity of raptor nests in the open tundra.<ref name= Voous/> In addition, most competing predators of the Arctic, excepting the very large mammals, are probably vulnerable to a hungry snowy owl.<ref name= Voous/><ref name= Holt/> In data from the [[Logan Airport]] alone over different winters, the snowy owls were observed to have preyed upon an impressive diversity of other raptorial birds: [[rough-legged buzzard]]s, [[American kestrel]]s (''Falco sparverius''), [[peregrine falcon]]s, [[barn owl]]s, other snowy owls, [[barred owl]]s (''Strix varia''), [[northern saw-whet owl]]s (''Aegolius acadicus'') and [[short-eared owl]]s. While owls are likely encountered during corresponding hunting times, it is likely that the swift falcons are usually ambushed at night (much as other ''Bubo'' owls will do).<ref name= Holt/><ref name= Smith/> In both the tundra and the wintering ground, there are several accounts of predation by snowy owls on short-eared owls.<ref name= Potapov/><ref name= Mikkola3/><ref>{{cite journal|doi=10.2307/1368028}}</ref> In addition, snowy owls have been known to prey on [[northern harrier]]s,<ref name= Holt/><ref name= Smith/> [[northern goshawk]]s (''Accipiter gentilis'')<ref name= Voous/> and [[gyrfalcon]]s.<ref name= Voous/><ref name= Mikkola3/> In a few cases, both juvenile and adult [[Arctic fox]]es have been known to fall prey to snowy owls.<ref name= Parker/><ref name= Stenkewitz/><ref name= Krechmar/><ref name="Gilg">{{cite journal|doi=10.1111/j.2006.0030-1299.14125.x}}</ref><ref>{{cite journal|title=''Alopex lagopus''|doi=10.1644/0.713.1}}</ref> A wintering snowy owl in [[Saskatchewan]] was observed to have preyed on an adult [[red fox]] (''Vulpes vulpes''). Predation by snowy owls on red foxes was also reported in the [[Irkutsky District]] of Russia. With an adult weight around {{convert|6|kg|lb|abbr=on}} (and far from defenseless), red fox may be the largest known prey known for snowy owls.<ref name= Maleev/><ref>{{cite journal|doi=10.29173/bluejay3979}}</ref> Besides aforementioned predation on domestic cats and skunks, several members of the [[weasel]] family, both small and relatively large, are known to be opportunistically hunted by snowy owls.<ref name= Potapov/><ref name= Voous/><ref name= Holt/><ref name= Smith/><ref name= Hakala/><ref>{{cite journal|doi=10.2307/3565424}}</ref> As a result of its potential predator status, the snowy owl is frequently mobbed at all times of the year by other predatory birds, including fierce dive-bombing by several of the northern falcons on the wintering grounds, including even by the relatively tiny but fierce and very agile [[Merlin (bird)|merlin]] (''Falco columbarius''). The much bulkier snowy owls cannot match the speed and flight ability of a falcon, ai may be almost relentlessly tormented by some birds such as peregrines.<ref name= Voous/><ref name= Mikkola3/><ref>{{cite journal|doi=10.29173/bluejay208}}</ref> +Almost certainly more often than being victim of other predators, snowy owls are known to dominate, kill and feed on a large diversity of other predators.<ref name= Voous/><ref name= Mikkola3/> Snowy owls, much like other ''Bubo'' owls, will opportunistically kill other birds of prey and predators. Although they will readily plunder the nests of other raptorial birds given the opportunity, most predations are on full-grown raptorial birds during winter due to the scarcity of raptor nests in the open tundra.<ref name= Voous/> In addition, most competing predators of the Arctic, excepting the very large mammals, are probably vulnerable to a hungry snowy owl.<ref name= Voous/><ref name= Holt/> In data from the [[Logan Airport]] alone over different winters, the snowy owls were observed to have preyed upon an impressive diversity of other raptorial birds: [[rough-legged buzzard]]s, [[American kestrel]]s (''Falco sparverius''), [[peregrine falcon]]s, [[barn owl]]s, other snowy owls, [[barred owl]]s (''Strix varia''), [[northern saw-whet owl]]s (''Aegolius acadicus'') and [[short-eared owl]]s. While owls are likely encountered during corresponding hunting times, it is likely that the swift falcons are usually ambushed at night (much as other ''Bubo'' owls will do).<ref name= Holt/> In both the tundra and the wintering ground, there are several accounts of predation by snowy owls on short-eared owls.<ref name= Potapov/><ref name= Mikkola3/><ref>{{cite journal|doi=10.2307/1368028}}</ref> In addition, snowy owls have been known to prey on [[northern harrier]]s,<ref name= Holt/> [[northern goshawk]]s (''Accipiter gentilis'')<ref name= Voous/> and [[gyrfalcon]]s.<ref name= Voous/><ref name= Mikkola3/> In a few cases, both juvenile and adult [[Arctic fox]]es have been known to fall prey to snowy owls.<ref name= Parker/><ref name= Stenkewitz/><ref name= Krechmar/><ref name="Gilg">{{cite journal|doi=10.1111/j.2006.0030-1299.14125.x}}</ref><ref>{{cite journal|title=''Alopex lagopus''|doi=10.1644/0.713.1}}</ref> A wintering snowy owl in [[Saskatchewan]] was observed to have preyed on an adult [[red fox]] (''Vulpes vulpes''). Predation by snowy owls on red foxes was also reported in the [[Irkutsky District]] of Russia. With an adult weight around {{convert|6|kg|lb|abbr=on}} (and far from defenseless), red fox may be the largest known prey known for snowy owls.<ref name= Maleev/><ref>{{cite journal|doi=10.29173/bluejay3979}}</ref> Besides aforementioned predation on domestic cats and skunks, several members of the [[weasel]] family, both small and relatively large, are known to be opportunistically hunted by snowy owls.<ref name= Potapov/><ref name= Voous/><ref name= Holt/><ref name= Hakala/><ref>{{cite journal|doi=10.2307/3565424}}</ref> As a result of its potential predator status, the snowy owl is frequently mobbed at all times of the year by other predatory birds, including fierce dive-bombing by several of the northern falcons on the wintering grounds, including even by the relatively tiny but fierce and very agile [[Merlin (bird)|merlin]] (''Falco columbarius''). The much bulkier snowy owls cannot match the speed and flight ability of a falcon, ai may be almost relentlessly tormented by some birds such as peregrines.<ref name= Voous/><ref name= Mikkola3/><ref>{{cite journal|doi=10.29173/bluejay208}}</ref> ==Breeding== ===Pair bond and breeding territory=== -In Utqiaġvik, of 239 recorded breeding attempts, 232 were monogamous, the other 7 [[Bigamy|social bigamy]].<ref name= Holt/> On [[Baffin Island]], 1 male bred with 2 females and sired 11 total fledged young.<ref name= Watson/> Another case of bigamy was reported in Norway where the 2 females bred to one male were {{convert|1.3|km|mi|abbr=on}} apart in nest site location.<ref name= Hagen/> On Feltar from 1967 to 1975, a male breed with two females, 1 younger and was possibly his own [[Incest|daughter]]. In the Feltar males first time breeding with both females, he did not bring food to the younger female. However, when older female disappeared the following year, the male and younger female producing 4 young, but disappeared the subsequent year altogether in 1975.<ref name= Robinson/> There are also unconfirmed cases of [[polyandry]], with 1 female being fed by 2 males. Snowy owls can breed once per year but when food is scarce many do not even attempt to breed.<ref name= Konig/><ref name= Voous/> Despite frequent wandering in search of food, they generally adhere more so than to a strict breeding season than [[short-eared owl]]s nesting in the tundra.<ref name= Voous/> 9 radio-tagged female snowy owls about [[Bylot Island]] were tracked to study how pre-laying snow cover effects their searching behavior for breeding area. These tracked females searched an average of 36 days and covered an average of {{convert|1251|km|mi|abbr=on}}. It is thought that the male and female mutually find an attractive breeding spot independently and converge.<ref>{{cite journal|doi=10.1186/s40462-015-0028-7}}</ref> The breeding territory normally averages about {{convert|2.6|km2|sqmi|abbr=on}} as in both [[Baffin Island]] and [[Ellesmere Island]] but varies in accordance to abundance of food and density of owls.<ref name= Konig/><ref name= Watson/><ref name= MacDonald/> Nesting territories average at Baffin island in the range of {{convert|8|to|10|km2|sqmi|abbr=on}} during poor lemming years.<ref name= Watson/> Nesting territories may up to {{convert|22|km2|sqmi|abbr=on}} on [[Southampton Island]] and had a mean distance of {{convert|4.5|km|mi|abbr=on}} between active nests.<ref name= Sutton1/> In Utqiaġvik, nesting pairs can vary from none to at least 7 and the territories average {{convert|5|to|10|km2|sqmi|abbr=on}}, with mean nest distances of {{convert|1.5|to|6|km|mi|abbr=on}}.<ref name= Pitelka/> In the Norwegian highlands, nesting occurs only at times of plenty distances of {{convert|1.2|to|3.7|km|mi|abbr=on}} between nests, averaging {{convert|2.1|km|mi|abbr=on}}.<ref name= Hagen/> Males marks territory with singing and display flights and likely always initiates.<ref name= Watson/> During the display, he engages in exaggerated wing beats with a shallow undulating and bouncy courtship flight with wings held in a [[Dihedral (aeronautics)|dihedral]]. He often drops to the ground but then flies again to only glide gently back down. Overall, the flight is somewhat reminiscent of the flight of a [[moth]].<ref name= Watson/><ref name= Pitelka/><ref name= Tulloch/><ref name= Robinson/> Females will answer her mate with her song during courtship.<ref name= Konig/> While courting, the male often also carries a lemming in his bill, then bows with cocked tail, similarly as in related owls (seldom displaying some other prey like [[snow bunting]]s). He then flaps his wings open in an emphatic manner, with the ground display being relatively brief (about 5 minutes). The female may possibly refuse to breed if ritual not performed.<ref name= Watson/><ref name= Taylor/> A possible courtship was engaged in by a male in southern Saskatchewan when a female was sighted.<ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v094n01/p0079-p0081.pdf|author1=Boxall, P. C. |author2= Lein, M. R. |year=1982|title=Possible courtship behavior of Snowy Owls in winter|journal= Wilson Bulletin|volume= 94|pages=79–81}}</ref> On Southampton Island, at least 20 males observed in late May in a "lemming year".<ref name= Voous/><ref name= Sutton1/> Nesting territory defense displays, not highly different from courtship displays, includes undulating flight and stiffly raised wings with bouts of exaggerated, delayed wing beats, looking like enormous white moths exposing their white wings under the sun.<ref name= Taylor/> At times, competing males will interlock claws in mid-air.<ref name= Voous/> Territorial and nuptial displays are followed by a ground display by the male with the wings arched up in an "angel" posture, visible for well over a mile.<ref name= Voous/> +In Utqiaġvik, of 239 recorded breeding attempts, 232 were monogamous, the other 7 [[Bigamy|social bigamy]].<ref name= Holt/> On [[Baffin Island]], 1 male bred with 2 females and sired 11 total fledged young.<ref name= Watson/> Another case of bigamy was reported in Norway where the 2 females bred to one male were {{convert|1.3|km|mi|abbr=on}} apart in nest site location.<ref name= Hagen/> On Feltar from 1967 to 1975, a male breed with two females, 1 younger and was possibly his own [[Incest|daughter]]. In the Feltar males first time breeding with both females, he did not bring food to the younger female. However, when older female disappeared the following year, the male and younger female producing 4 young, but disappeared the subsequent year altogether in 1975.<ref name= Robinson/> There are also unconfirmed cases of [[polyandry]], with 1 female being fed by 2 males. Snowy owls can breed once per year but when food is scarce many do not even attempt to breed.<ref name= Konig/><ref name= Voous/> Despite frequent wandering in search of food, they generally adhere more so than to a strict breeding season than [[short-eared owl]]s nesting in the tundra.<ref name= Voous/> 9 radio-tagged female snowy owls about [[Bylot Island]] were tracked to study how pre-laying snow cover effects their searching behavior for breeding area. These tracked females searched an average of 36 days and covered an average of {{convert|1251|km|mi|abbr=on}}. It is thought that the male and female mutually find an attractive breeding spot independently and converge.<ref>{{cite journal|doi=10.1186/s40462-015-0028-7}}</ref> The breeding territory normally averages about {{convert|2.6|km2|sqmi|abbr=on}} as in both [[Baffin Island]] and [[Ellesmere Island]] but varies in accordance to abundance of food and density of owls.<ref name= Konig/><ref name= Watson/> Nesting territories average at Baffin island in the range of {{convert|8|to|10|km2|sqmi|abbr=on}} during poor lemming years.<ref name= Watson/> Nesting territories may up to {{convert|22|km2|sqmi|abbr=on}} on [[Southampton Island]] and had a mean distance of {{convert|4.5|km|mi|abbr=on}} between active nests.<ref name= Sutton1/> In Utqiaġvik, nesting pairs can vary from none to at least 7 and the territories average {{convert|5|to|10|km2|sqmi|abbr=on}}, with mean nest distances of {{convert|1.5|to|6|km|mi|abbr=on}}.<ref name= Pitelka/> In the Norwegian highlands, nesting occurs only at times of plenty distances of {{convert|1.2|to|3.7|km|mi|abbr=on}} between nests, averaging {{convert|2.1|km|mi|abbr=on}}.<ref name= Hagen/> Males marks territory with singing and display flights and likely always initiates.<ref name= Watson/> During the display, he engages in exaggerated wing beats with a shallow undulating and bouncy courtship flight with wings held in a [[Dihedral (aeronautics)|dihedral]]. He often drops to the ground but then flies again to only glide gently back down. Overall, the flight is somewhat reminiscent of the flight of a [[moth]].<ref name= Watson/><ref name= Pitelka/><ref name= Tulloch/><ref name= Robinson/> Females will answer her mate with her song during courtship.<ref name= Konig/> While courting, the male often also carries a lemming in his bill, then bows with cocked tail, similarly as in related owls (seldom displaying some other prey like [[snow bunting]]s). He then flaps his wings open in an emphatic manner, with the ground display being relatively brief (about 5 minutes). The female may possibly refuse to breed if ritual not performed.<ref name= Watson/><ref name= Taylor/> A possible courtship was engaged in by a male in southern Saskatchewan when a female was sighted.<ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v094n01/p0079-p0081.pdf|author1=Boxall, P. C. |author2= Lein, M. R. |year=1982|title=Possible courtship behavior of Snowy Owls in winter|journal= Wilson Bulletin|volume= 94|pages=79–81}}</ref> On Southampton Island, at least 20 males observed in late May in a "lemming year".<ref name= Voous/><ref name= Sutton1/> Nesting territory defense displays, not highly different from courtship displays, includes undulating flight and stiffly raised wings with bouts of exaggerated, delayed wing beats, looking like enormous white moths exposing their white wings under the sun.<ref name= Taylor/> At times, competing males will interlock claws in mid-air.<ref name= Voous/> Territorial and nuptial displays are followed by a ground display by the male with the wings arched up in an "angel" posture, visible for well over a mile.<ref name= Voous/> ===Nest sites=== [[File:Tundra Polygons and Pingos (9514080830).jpg|thumb|left|Snowy owls often seek out polygons such as these in the [[tundra]].]] -Most individuals arrive at the nest site by April or May with a few overwintering arctic exceptions.<ref name= Murie/><ref name= Marine/><ref name= Pitelka2/><ref name= Fuller/> Males advertises potential nest sites to his mate by scratching the ground and spreading his wings over it.<ref name= Konig/> The nest is usually a shallow depression on a windswept eminence in the open tundra. There seems to be a variety of qualifiers for appropriate nest sites. The nest site is typically snow-free and dry relative to the surrounding environment, usually with a good view of the surrounding landscape. The nest may be made of [[ridge]]s, [[Mound|elevated mound]]s, high [[polygon]]s, [[hummock]]s, hills, man-made mounds and occasionally [[Outcrop|rocky outcrops]]. If covered with vegetation, taller plants that may obstruct view are plucked away sometimes.<ref name= Konig/><ref name= Voous/><ref name= Watson/><ref name= Pitelka2/><ref name= Holt3>{{cite journal|doi=10.5253/078.097.0422}}</ref> The nest sites are often long-established and naturally created by the freeze-thaw process of the tundra.<ref name= Voous/><ref name= Holt/> [[Bar (river morphology)|Gravel bars]] may be used as well.<ref name= Potapov/> The female may take the most active role in the nest's condition of any owl species.<ref name= Holt/><ref name= Mikkola/> No owl build their own nests but female snowy owls take about three days constructing a scrape, digging with her claws and rotating until a fairly circular bowl is formed. She will still not construct or add foreign materials to the nest (despite some circumstantial evidence of moss and grass from outside the nest mound being found).<ref name= Holt/><ref name= Murie/><ref name= Tulloch/> In two separate cases in Utqiaġvik, two separate females dug out a second scrape to the side and below the main nests and appeared to have called all chicks to the more secluded nest to ride out severe weather until the skies cleared.<ref name= Holt/> The Utqiaġvik nest scrapes averaged {{convert|47.7|x|44|cm|in|abbr=on}} in 91 with a mean depth of {{convert|9.8|cm|in|abbr=on}} while the scrapes were smaller in [[Hooper Bay]], reportedly {{convert|25|to|33|cm|in|abbr=on}} diameter and {{convert|4|to|9|cm|in|abbr=on}} in depth.<ref name= Murie/><ref name= Holt3/> Occasionally, in the lower tundra, snowy owls may too use old nests of [[rough-legged buzzard]]s as well as abandoned [[eagle]] nests.<ref name= Voous/> Unlike other northerly breeding raptorial birds, the snowy owl is not known to nest on cliffs and the like, so do not enter into direct competition with eagles, falcons, ravens or other ''Bubo'' owls when nesting to the relative south.<ref name= Voous/> The area of nest mound often has a relatively rich plant life which attract the lemmings, which may tunnel right under and around the owl's nest.<ref name= Voous/> [[Goose|Geese]], ducks and [[shorebird]]s of several species known to gain incidental protection by nesting close to snowy owls. Conversely, the snowy owls will sometimes kill and eat both young and adults of these birds, which implies a trade-off in the benefits.<ref name= Parmelee/><ref name= Murie/><ref name= Robinson/><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v109n03/p0449-p0461.pdf|author=Tremblay, J. P., Gauthier, G., Lepage, D., & Desrochers, A. |year=1997|title=Factors affecting nesting success in greater snow geese: Effects of habitat and association with snowy owls|journal= The Wilson Bulletin|pages= 449–461|volume=109|issue=3|jstor=4163840}}</ref><ref>{{cite journal|doi=10.1139/z96-210}}</ref><ref>{{cite journal|doi=10.1007/BF02465456|title=How do Brent Geese (''Branta b. bernicla'') cope with evil}}</ref><ref>Smith, P. A. (2003). ''Factors affecting nest site selection and reproductive success of tundra nesting shorebirds'' (Doctoral dissertation, University of British Columbia).</ref> +Most individuals arrive at the nest site by April or May with a few overwintering arctic exceptions.<ref name= Murie/><ref name= Marine/><ref name= Pitelka2/> Males advertises potential nest sites to his mate by scratching the ground and spreading his wings over it.<ref name= Konig/> The nest is usually a shallow depression on a windswept eminence in the open tundra. There seems to be a variety of qualifiers for appropriate nest sites. The nest site is typically snow-free and dry relative to the surrounding environment, usually with a good view of the surrounding landscape. The nest may be made of [[ridge]]s, [[Mound|elevated mound]]s, high [[polygon]]s, [[hummock]]s, hills, man-made mounds and occasionally [[Outcrop|rocky outcrops]]. If covered with vegetation, taller plants that may obstruct view are plucked away sometimes.<ref name= Konig/><ref name= Voous/><ref name= Watson/><ref name= Pitelka2/><ref name= Holt3>{{cite journal|doi=10.5253/078.097.0422}}</ref> The nest sites are often long-established and naturally created by the freeze-thaw process of the tundra.<ref name= Voous/><ref name= Holt/> [[Bar (river morphology)|Gravel bars]] may be used as well.<ref name= Potapov/> The female may take the most active role in the nest's condition of any owl species.<ref name= Holt/><ref name= Mikkola/> No owl build their own nests but female snowy owls take about three days constructing a scrape, digging with her claws and rotating until a fairly circular bowl is formed. She will still not construct or add foreign materials to the nest (despite some circumstantial evidence of moss and grass from outside the nest mound being found).<ref name= Holt/><ref name= Murie/><ref name= Tulloch/> In two separate cases in Utqiaġvik, two separate females dug out a second scrape to the side and below the main nests and appeared to have called all chicks to the more secluded nest to ride out severe weather until the skies cleared.<ref name= Holt/> The Utqiaġvik nest scrapes averaged {{convert|47.7|x|44|cm|in|abbr=on}} in 91 with a mean depth of {{convert|9.8|cm|in|abbr=on}} while the scrapes were smaller in [[Hooper Bay]], reportedly {{convert|25|to|33|cm|in|abbr=on}} diameter and {{convert|4|to|9|cm|in|abbr=on}} in depth.<ref name= Murie/><ref name= Holt3/> Occasionally, in the lower tundra, snowy owls may too use old nests of [[rough-legged buzzard]]s as well as abandoned [[eagle]] nests.<ref name= Voous/> Unlike other northerly breeding raptorial birds, the snowy owl is not known to nest on cliffs and the like, so do not enter into direct competition with eagles, falcons, ravens or other ''Bubo'' owls when nesting to the relative south.<ref name= Voous/> The area of nest mound often has a relatively rich plant life which attract the lemmings, which may tunnel right under and around the owl's nest.<ref name= Voous/> [[Goose|Geese]], ducks and [[shorebird]]s of several species known to gain incidental protection by nesting close to snowy owls. Conversely, the snowy owls will sometimes kill and eat both young and adults of these birds, which implies a trade-off in the benefits.<ref name= Parmelee/><ref name= Murie/><ref name= Robinson/><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v109n03/p0449-p0461.pdf|author=Tremblay, J. P., Gauthier, G., Lepage, D., & Desrochers, A. |year=1997|title=Factors affecting nesting success in greater snow geese: Effects of habitat and association with snowy owls|journal= The Wilson Bulletin|pages= 449–461|volume=109|issue=3|jstor=4163840}}</ref><ref>{{cite journal|doi=10.1139/z96-210}}</ref><ref>{{cite journal|doi=10.1007/BF02465456|title=How do Brent Geese (''Branta b. bernicla'') cope with evil}}</ref><ref>Smith, P. A. (2003). ''Factors affecting nest site selection and reproductive success of tundra nesting shorebirds'' (Doctoral dissertation, University of British Columbia).</ref> ===Eggs=== @@ -145,19 +145,19 @@ ===Parental behavior=== [[File:SnowyOwl2.jpg|thumb|left|A captive mother snowy owl with its chick.]] -Food is brought to the nest by males and surplus food is stored nearby.<ref name= Konig/> Females in breeding season often develop a very extensive [[brood patch]] which in this species is a fairly enormous, high vascularized featherless area of pink belly skin.<ref name= Voous/><ref name= Parmelee/> Incubation lasts 31.8–33 days (unconfirmed and possibly dubious reports from as little as 27 to as much as 38-day incubations).<ref name= Konig/><ref name= Murie/><ref name= Robinson/><ref name= Schaanning/> The female alone broods the young, often while simultaneously incubating still unhatched eggs.<ref name= Konig/><ref name= Holt/> Sometimes older chicks incidentally brood their younger siblings and females may shelter the young under her wings during inclement weather.<ref name= Parmelee/><ref name= Watson/> When first feeding the young, the female may dismantle prey to feed the young only the softer body parts then gradually ramping up the size of proportions until they eat a whole prey item.<ref name= Watson/> Aggressive encounters with parent snowy owls are said to be "genuinely dangerous" and one resource claimed the snowy owl to be the bird species with the most formidable nest defense displays towards humans.<ref name= Voous/><ref name= Bent/><ref>Couzens, D. (2008). ''Extreme Birds: The World's Most Extraordinary and Bizarre Birds''. Firefly Books.</ref> The usual response to sighted humans near the nest is mild but continued approach begins to increasingly irritate the parents.<ref name= Holt/> At times, humans are forcefully dive-bombed upon, while other potential threats are dealt with in a “forward-threat” where the male walks towards the intruders, engaging in impressive feather-raising and fanning out of half-spread wings until they run forward and slash with both their feet and bill.<ref name= Voous/><ref name= Bent/><ref name= Watson/><ref name= Sutton1/><ref name= Parmelee/> Fairly serious injuries have been sustained in the worst of snowy owl defensive attacks, including cranial trauma, requiring researchers to make the long trek back to medical care, although human fatalities are not known.<ref name= Sutton/><ref>Barth, E. K. (1950). ''Efter fjallugglor pf Hardangervidda''. Fauna Flora, 45: 235–242.</ref> Snowy owl parents have been seen to aggressively attacked glaucous gulls, arctic fox and dogs in breeding ground in Utqiaġvik.<ref name= Holt/> Non-predatory animals like [[Reindeer|caribou]] in Utqiaġvik and sheep (''Ovis aries'') in Fetlar are attacked as well, possibly to avoid potential trampling of the eggs or the young.<ref name= Parmelee/><ref name= Tulloch/> Males are said to do the majority of nest defense but the female will also often become involved as well.<ref name= Holt/> Analysis showed in [[Lapland, Sweden]], that females in nest defense against people engaged in vocal displays (warning and mewing calls) and that males did not engage in mewing but did engage in most hooting calls, many warning calls and almost all physical attacks.<ref name= Wiklund>Wiklund, C. G., & Stigh, J. (1983). ''Nest defence and evolution of reversed sexual size dimorphism in Snowy Owls Nyctea scandiaca''. Ornis Scandinavica, 58–62.</ref> In other instances, [[distraction display]]s are engaged in against predators, with a "broken-wing act" including high, thin squeals interspersed with weird squeaks, often taking flight only to quickly fall from the sky and imitate a struggle.<ref name= Voous/><ref>[http://animaldiversity.ummz.umich.edu/site/accounts/information/Nyctea_scandiaca.html ADW: ''Nyctea scandiaca: Information'']. Animaldiversity.ummz.umich.edu. Retrieved on 19 October 2010.</ref> One author recorded a male to draw him about {{convert|2|km|mi|abbr=on}} from the nest before ceasing.<ref name= Parmelee/> 77% of 45 distraction displays in Lapland, Sweden were by females.<ref name= Wiklund/> +Food is brought to the nest by males and surplus food is stored nearby.<ref name= Konig/> Females in breeding season often develop a very extensive [[brood patch]] which in this species is a fairly enormous, high vascularized featherless area of pink belly skin.<ref name= Voous/><ref name= Parmelee/> Incubation lasts 31.8–33 days (unconfirmed and possibly dubious reports from as little as 27 to as much as 38-day incubations).<ref name= Konig/><ref name= Murie/><ref name= Robinson/><ref name= Schaanning/> The female alone broods the young, often while simultaneously incubating still unhatched eggs.<ref name= Konig/><ref name= Holt/> Sometimes older chicks incidentally brood their younger siblings and females may shelter the young under her wings during inclement weather.<ref name= Parmelee/><ref name= Watson/> When first feeding the young, the female may dismantle prey to feed the young only the softer body parts then gradually ramping up the size of proportions until they eat a whole prey item.<ref name= Watson/> Aggressive encounters with parent snowy owls are said to be "genuinely dangerous" and one resource claimed the snowy owl to be the bird species with the most formidable nest defense displays towards humans.<ref name= Voous/><ref name= Bent/><ref>Couzens, D. (2008). ''Extreme Birds: The World's Most Extraordinary and Bizarre Birds''. Firefly Books.</ref> The usual response to sighted humans near the nest is mild but continued approach begins to increasingly irritate the parents.<ref name= Holt/> At times, humans are forcefully dive-bombed upon, while other potential threats are dealt with in a “forward-threat” where the male walks towards the intruders, engaging in impressive feather-raising and fanning out of half-spread wings until they run forward and slash with both their feet and bill.<ref name= Voous/><ref name= Bent/><ref name= Watson/><ref name= Sutton1/><ref name= Parmelee/> Fairly serious injuries have been sustained in the worst of snowy owl defensive attacks, including cranial trauma, requiring researchers to make the long trek back to medical care, although human fatalities are not known.<ref name= Sutton/> Snowy owl parents have been seen to aggressively attacked glaucous gulls, arctic fox and dogs in breeding ground in Utqiaġvik.<ref name= Holt/> Non-predatory animals like [[Reindeer|caribou]] in Utqiaġvik and sheep (''Ovis aries'') in Fetlar are attacked as well, possibly to avoid potential trampling of the eggs or the young.<ref name= Parmelee/><ref name= Tulloch/> Males are said to do the majority of nest defense but the female will also often become involved as well.<ref name= Holt/> Analysis showed in [[Lapland, Sweden]], that females in nest defense against people engaged in vocal displays (warning and mewing calls) and that males did not engage in mewing but did engage in most hooting calls, many warning calls and almost all physical attacks.<ref name= Wiklund>{{cite journal|title=Nest defence and evolution of reversed sexual size dimorphism in Snowy Owls ''Nyctea scandiaca''|doi=10.2307/3676252}}</ref> In other instances, [[distraction display]]s are engaged in against predators, with a "broken-wing act" including high, thin squeals interspersed with weird squeaks, often taking flight only to quickly fall from the sky and imitate a struggle.<ref name= Voous/><ref>[http://animaldiversity.ummz.umich.edu/site/accounts/information/Nyctea_scandiaca.html ADW: ''Nyctea scandiaca: Information'']. Animaldiversity.ummz.umich.edu. Retrieved on 19 October 2010.</ref> One author recorded a male to draw him about {{convert|2|km|mi|abbr=on}} from the nest before ceasing.<ref name= Parmelee/> 77% of 45 distraction displays in Lapland, Sweden were by females.<ref name= Wiklund/> ===Development of young=== [[File:Young snowy owls (69120).jpg|thumb|An old photo of snowy owl nestlings on [[Baffin Island]].]] -Hatching intervals are generally from 1 to 3 days, quite often within 37–45 hours apart.<ref name= Watson/><ref name= Tulloch/> New chicks are [[Altriciality|semi-altricial]] (i.e. typically helpless and blind), initially being white and rather wet but dry by the end of the first day. The weight of 7 hatchlings was {{convert|35|to|55|g|oz|abbr=on}}, with an average of {{convert|46|g|oz|abbr=on}} while 3 were {{convert|44.7|g|oz|abbr=on}}.<ref name= Parmelee/><ref name= Watson/> Due to the pronounced asynchrony of the egg-laying and hatching, the size difference between siblings can be enormous and in some cases when the smallest chick weighs only {{convert|20|to|50|g|oz|abbr=on}}, the biggest chick already has attained a weight of around {{convert|350|to|380|g|oz|abbr=on}}.<ref name= Watson/><ref name= Barth/> When the oldest chick is about 3 weeks, the female will start to hunt as well as the male and both may directly feed the young although in some cases they may not need hunt very much if lemmings are particularly numerous.<ref name= Konig/><ref name= Voous/> [[Hoarding (animal behavior)|Caches]] of lemmings around a nest may include more than 80 lemmings that can support the family.<ref name= Voous/> Unlike many owls, the chicks of snowy owls are not known to behave aggressively toward one another or to engage in [[siblicide]], perhaps in part due to the need for energy conservance.<ref name= Holt/><ref name= Tulloch/> Some cases of [[cannibalism]] of chicks by the family group were thought to be cases where chicks die from other causes.<ref name= Sutton/> When they are about 2 weeks, the chicks may begin to walk around the nest site which they leave by 18–28 days, although they are still unable to fly and may find safety in nooks and crannies of vegetation and rocks usually only about {{convert|1|to|2|m|ft|abbr=on}} from the nest mound, as well as via their parents defense.<ref name= Konig/><ref name= Voous/><ref name= Romero>Romero, L. M., Holt, D. W. Maples M. & Wingfield, J. C.. (2006). ''Corticosterone is not correlated with nest departure in Snowy Owl chicks (Nyctea scandiaca)''. General and Comparative Endocrinology 149 (2): 119–123.</ref> Leaving the nest is thought to likely be an anti-predator strategy.<ref name= Holt/><ref>Holt, D. W. & Leasure, S. M. (1993). ''Short-eared Owl (Asio flammeus)''. In: ''The birds of North America, No. 62'', edited by A. Poole and F. Gill. Washington, DC: Acad. Nat. Sci., Philadelphia, PA; Am. Ornithol. Union.</ref> The male snowy owl may drop fresh prey deliveries directly on the ground near the wandering young.<ref name= Voous/> After about three weeks of age, the young may wander fairly widely, rarely to {{convert|1|km|mi|abbr=on}}, but usually stay within {{convert|500|m|ft|abbr=on}} of the nest mound.<ref name= Watson/><ref name= Tulloch/> Threat postures by young in reaction to researchers were first noticeable at about 20–25 days of age and common at about 28 days and the chicks can be impressively quick and agile-footed.<ref name= Holt/><ref name= Watson/> The first fledgling occurs at around 35–50 days, and by 50–60 days the young can fly well and hunt on their own.<ref name= Konig/><ref name= Voous/> The total care period is for 2–3.5 months, increasing in length with increased size of the brood.<ref name= Konig/><ref name= Parmelee/> Although independence was once thought to be sought by late August or early September but is more likely by late September to October when migration season for the species begins.<ref name= Holt/><ref name= Pitelka2/> The nesting cycle is similar in length to the Arctic short-eared owls and faster than Eurasian eagle-owls by up to 2 months.<ref name= Schrezinger>Schrezinger, W. (1974). ''Zur Ethologie und Jugendentwicklung der Schnee-Eule Nyctea scandiaca nach Beobachtungen in Gefangenschaft''. J. Orn, 115: 8–49.</ref> +Hatching intervals are generally from 1 to 3 days, quite often within 37–45 hours apart.<ref name= Watson/><ref name= Tulloch/> New chicks are [[Altriciality|semi-altricial]] (i.e. typically helpless and blind), initially being white and rather wet but dry by the end of the first day. The weight of 7 hatchlings was {{convert|35|to|55|g|oz|abbr=on}}, with an average of {{convert|46|g|oz|abbr=on}} while 3 were {{convert|44.7|g|oz|abbr=on}}.<ref name= Parmelee/><ref name= Watson/> Due to the pronounced asynchrony of the egg-laying and hatching, the size difference between siblings can be enormous and in some cases when the smallest chick weighs only {{convert|20|to|50|g|oz|abbr=on}}, the biggest chick already has attained a weight of around {{convert|350|to|380|g|oz|abbr=on}}.<ref name= Watson/> When the oldest chick is about 3 weeks, the female will start to hunt as well as the male and both may directly feed the young although in some cases they may not need hunt very much if lemmings are particularly numerous.<ref name= Konig/><ref name= Voous/> [[Hoarding (animal behavior)|Caches]] of lemmings around a nest may include more than 80 lemmings that can support the family.<ref name= Voous/> Unlike many owls, the chicks of snowy owls are not known to behave aggressively toward one another or to engage in [[siblicide]], perhaps in part due to the need for energy conservance.<ref name= Holt/><ref name= Tulloch/> Some cases of [[cannibalism]] of chicks by the family group were thought to be cases where chicks die from other causes.<ref name= Sutton/> When they are about 2 weeks, the chicks may begin to walk around the nest site which they leave by 18–28 days, although they are still unable to fly and may find safety in nooks and crannies of vegetation and rocks usually only about {{convert|1|to|2|m|ft|abbr=on}} from the nest mound, as well as via their parents defense.<ref name= Konig/><ref name= Voous/><ref name= Romero>Romero, L. M., Holt, D. W. Maples M. & Wingfield, J. C.. (2006). ''Corticosterone is not correlated with nest departure in Snowy Owl chicks (Nyctea scandiaca)''. General and Comparative Endocrinology 149 (2): 119–123.</ref> Leaving the nest is thought to likely be an anti-predator strategy.<ref name= Holt/><ref>Holt, D. W. & Leasure, S. M. (1993). ''Short-eared Owl (Asio flammeus)''. In: ''The birds of North America, No. 62'', edited by A. Poole and F. Gill. Washington, DC: Acad. Nat. Sci., Philadelphia, PA; Am. Ornithol. Union.</ref> The male snowy owl may drop fresh prey deliveries directly on the ground near the wandering young.<ref name= Voous/> After about three weeks of age, the young may wander fairly widely, rarely to {{convert|1|km|mi|abbr=on}}, but usually stay within {{convert|500|m|ft|abbr=on}} of the nest mound.<ref name= Watson/><ref name= Tulloch/> Threat postures by young in reaction to researchers were first noticeable at about 20–25 days of age and common at about 28 days and the chicks can be impressively quick and agile-footed.<ref name= Holt/><ref name= Watson/> The first fledgling occurs at around 35–50 days, and by 50–60 days the young can fly well and hunt on their own.<ref name= Konig/><ref name= Voous/> The total care period is for 2–3.5 months, increasing in length with increased size of the brood.<ref name= Konig/><ref name= Parmelee/> Although independence was once thought to be sought by late August or early September but is more likely by late September to October when migration season for the species begins.<ref name= Holt/><ref name= Pitelka2/> The nesting cycle is similar in length to the Arctic short-eared owls and faster than Eurasian eagle-owls by up to 2 months.<ref name= Schrezinger>Schrezinger, W. (1974). ''Zur Ethologie und Jugendentwicklung der Schnee-Eule Nyctea scandiaca nach Beobachtungen in Gefangenschaft''. J. Orn, 115: 8–49.</ref> ===Maturity and nesting success=== [[File:SNOWY OWL, Canada.jpg|thumb|left|Snowy owl, juvenile, in Ontario, Canada.]] -Sexual maturity reached the following year but the first breeding is normally at no sooner than the end of the second year of life.<ref name= Konig/> There is little strong evidence of typical age of first breeding but initial breeding by males could be inferred by the plumage of males in Utqiaġvik by plumage. At that stage, which the males were essentially all pure white, most were aged to about 3 to 4 years old.<ref name= Holt/> The snowy owl seems to markedly inconsistent in regard to breeding every year, often taking at least up to two years between attempts and sometimes as much as nearly a decade.<ref name= Potapov/><ref name= Fuller/> 7 satellite-marking females in Canada proved that they did breed in consecutive years, with 1 breeding over 3 consecutive years.<ref name= Therrien/> In 23 years at Utqiaġvik, snowys bred in 13 of them.<ref name= Holt/><ref name= Fuller/> Nesting success can reach 90–100% in even the largest clutches in high lemming years.<ref name= Voous/> While over the course of 21 years, 260 total nests were recorded in Utqiaġvik. There, from 4–54 nests were recorded annually. The Utqiaġvik nests bore 3 to 10 sized-clutches with a mean of 6 eggs per nest and an annual mean hatching success from 39 to 91%. 31–87% of chicks were able to depart on foot and 48–65% were annually estimated to survive to fledge; elsewhere, 40% survived to fledge.<ref name= Holt/><ref name= Parmelee/> In another set, 97% of observed eggs both hatched and fledged.<ref name= Watson/> In Norway, the fledging success from 10 nests was much lower at about 46%.<ref name= Hagen/> Norwegian data, which previously indicated it to be an almost accidental breeder in northern Norway, indicates that it is a more regular breeder than expected, though. 3 good years were found for snowy owls between 1968 and 2005: 1974 (when there were 12 pairs), 1978 (22 pairs) and 1985 (20 pairs), with 14 additional locations when potential (but not confirmed) breeding has occurred.<ref name= Jacobsen/> The main determinable causes of nest failure were deemed to be [[starvation]] and [[Hypothermia|exposure]].<ref name= Holt/> A number of Norwegian and Finnish nests were known to fail due to severe [[black fly]] parasitism.<ref>Solheim, R., Jacobsen, K. O., Øien, I. J., Aarvak, T., & Polojärvi, P. (2013). ''Snowy Owl nest failures caused by blackfly attacks on incubating females''. Ornis Norvegica, 36, 1–5.</ref> +Sexual maturity reached the following year but the first breeding is normally at no sooner than the end of the second year of life.<ref name= Konig/> There is little strong evidence of typical age of first breeding but initial breeding by males could be inferred by the plumage of males in Utqiaġvik by plumage. At that stage, which the males were essentially all pure white, most were aged to about 3 to 4 years old.<ref name= Holt/> The snowy owl seems to markedly inconsistent in regard to breeding every year, often taking at least up to two years between attempts and sometimes as much as nearly a decade.<ref name= Potapov/> 7 satellite-marking females in Canada proved that they did breed in consecutive years, with 1 breeding over 3 consecutive years.<ref name= Therrien/> In 23 years at Utqiaġvik, snowys bred in 13 of them.<ref name= Holt/> Nesting success can reach 90–100% in even the largest clutches in high lemming years.<ref name= Voous/> While over the course of 21 years, 260 total nests were recorded in Utqiaġvik. There, from 4–54 nests were recorded annually. The Utqiaġvik nests bore 3 to 10 sized-clutches with a mean of 6 eggs per nest and an annual mean hatching success from 39 to 91%. 31–87% of chicks were able to depart on foot and 48–65% were annually estimated to survive to fledge; elsewhere, 40% survived to fledge.<ref name= Holt/><ref name= Parmelee/> In another set, 97% of observed eggs both hatched and fledged.<ref name= Watson/> In Norway, the fledging success from 10 nests was much lower at about 46%.<ref name= Hagen/> Norwegian data, which previously indicated it to be an almost accidental breeder in northern Norway, indicates that it is a more regular breeder than expected, though. 3 good years were found for snowy owls between 1968 and 2005: 1974 (when there were 12 pairs), 1978 (22 pairs) and 1985 (20 pairs), with 14 additional locations when potential (but not confirmed) breeding has occurred. The main determinable causes of nest failure were deemed to be [[starvation]] and [[Hypothermia|exposure]].<ref name= Holt/> A number of Norwegian and Finnish nests were known to fail due to severe [[black fly]] parasitism.<ref>{{cite journal|doi=10.15845/on.v36i0.394}}</ref> ==Longevity== -The snowy owl can live a long life for a bird.<ref name= Holt/> Records show that the oldest snowy owls in captivity can live to 25 to even 30 years of age.<ref name= Konig/><ref name= Holt/><ref>Schenker, A. (1978). Höchsalter europaischer Vögel im Zoologischen Garten Basel. Ornithol. Beob. 75: 96–97.</ref> Typical lifespans probably reach around 10 years in the wild.<ref name= Konig/><ref name= Mikkola/> The longest known lifespan in the wild was one that initially banded (possibly in its first winter) in [[Massachusetts]] and recovered dead in [[Montana]] 23 years and 10-month later.<ref name= Holt/> The annual survival rate for twelve females on [[Bylot Island]] was estimated at around 85–92.3%.<ref>{{cite journal|doi=10.1002/jwmg.414}}</ref> It is often reputed that snowy owls frequently died from starvation, with historical accounts frequently opined they "had to" leave their breeding grounds due to lemming "crashes" but would starve to the south.<ref name= Kerlinger/><ref name= Gross1/><ref name= Zettenberg>{{cite journal|doi=10.1898/NWN07-19.1}}</ref> However, it was proven fairly early on that snowy owls often do survive throughout the winter.<ref name= Bent/> This is reinforced somewhat by small radio-tracking and banding studies of the northern [[Great Plains]] and the intermountain [[valley]]s of the northwestern United States.<ref name= Zettenberg/><ref name= Kerlinger3>{{cite journal|doi=10.2307/1368844}}</ref> More circumstance evidence shows a lack of starvation in the eastern part of North America as well.<ref>{{cite journal|title=Winter irruptive Snowy Owls (''Bubo scandiacus'') in North America are not starving|doi=10.1139/cjz-2017-0278|url=https://www.researchgate.net/publication/322843463_Winter_irruptive_snowy_owls_in_North_America_are_not_starving}}</ref> There is evidence that some adults are known to return to the same wintering areas in ensuing years, areas which are far south of their breeding range.<ref>{{cite journal|doi=10.29173/bluejay1721}}</ref><ref>{{cite journal|author1=Follen, D. |author2= Luepke, K. |year=1980|title= Snowy Owl recaptures|journal= Inland Bird Banding |volume=52|pages= 60}}</ref> At Logan Airport, most snowy owls that are seen appear to be in good condition.<ref name= Holt/><ref name= Smith/> Of 71 dead snowy owls found in winter in the northern Great Plains, 86% died from assorted [[Major trauma|traumas]], including [[Roadkill|collisions]] with automobiles and other, usually manmade, objects as well as [[electrocution]]s and [[Culling|shootings]]. Only 14% of the 71 deaths were due to apparent starving. Data showed some owls appeared to incur injuries but healed and survived.<ref name= Kerlinger3/> More evidence was found in wintering snowy owls in New York of [[Bone healing|healed fractures]], though some may require surgery to recover.<ref>{{cite journal|pmid=30204018|title=Successful Management of Open, Contaminated Metacarpal Fractures in an Adult Snowy Owl (''Bubo scandiacus'') With a Minimal Type II External Skeletal Fixator}}</ref> 537 wintering birds in Saskatchewan were studied based on [[Fatty acid metabolism|fat reserves]], which were superior in females over males and adults over juveniles; while 31% of females lacked fat reserves, at least 45% of males found starving or in a state of infirmity were males and 63% turned into [[Wildlife rehabilitation]] centres were also males.<ref name= Chang/> In British Columbia, of 177 snowy owl deaths, of owls to die, only a small percentage were due to natural causes, such as assumed starvation at 13% and 12% were "found dead".<ref name= Campbell/> 1 fledgling on Fetlar dead due to [[pneumonia]] and ''[[Staphylococcus]]'' while a second died from ''[[Aspergillosis]]''.<ref name= Robinson/> Evidence shows that in Utqiaġvik during exceptionally prolonged rains (i.e. 2 to 3 days), nest-departed young in Utqiaġvik were vulnerable to starvation, leading to [[hypothermia]] and pneumonia.<ref name= Holt/> Due to their natural history, the snowy owl may be effected more severely by [[Parasitism|blood parasitism]] than other raptors, due to lowered [[Immunity (medical)|immunity]].<ref>{{cite journal|pmid=29517448|title=Clinical effect of hemoparasite infections in snowy owls (''Bubo scandiacus'')}}</ref> Conversely, they appear to have lower levels of ectoparasites like [[Mallophaga|chewing lice]] than in other large owls per large samples from [[Manitoba]]. The snowy owls averaged about 3.9 chewing lice per host against 7.5 for great grey owls and 10.5 for great horned owls.<ref>{{cite journal|doi=10.4039/tce.2019.42|title=Infestation parameters for chewing lice (Phthiraptera: Amblycera, Ischnocera) infesting owls (Aves: Strigidae, Tytonidae) in Manitoba, Canada}}</ref> +The snowy owl can live a long life for a bird.<ref name= Holt/> Records show that the oldest snowy owls in captivity can live to 25 to even 30 years of age.<ref name= Konig/><ref name= Holt/><ref>Schenker, A. (1978). Höchsalter europaischer Vögel im Zoologischen Garten Basel. Ornithol. Beob. 75: 96–97.</ref> Typical lifespans probably reach around 10 years in the wild.<ref name= Konig/><ref name= Mikkola/> The longest known lifespan in the wild was one that initially banded (possibly in its first winter) in [[Massachusetts]] and recovered dead in [[Montana]] 23 years and 10-month later.<ref name= Holt/> The annual survival rate for twelve females on [[Bylot Island]] was estimated at around 85–92.3%.<ref>{{cite journal|doi=10.1002/jwmg.414}}</ref> It is often reputed that snowy owls frequently died from starvation, with historical accounts frequently opined they "had to" leave their breeding grounds due to lemming "crashes" but would starve to the south.<ref name= Kerlinger/><ref name= Gross1/><ref name= Zettenberg>{{cite journal|doi=10.1898/NWN07-19.1}}</ref> However, it was proven fairly early on that snowy owls often do survive throughout the winter.<ref name= Bent/> This is reinforced somewhat by small radio-tracking and banding studies of the northern [[Great Plains]] and the intermountain [[valley]]s of the northwestern United States.<ref name= Zettenberg/><ref name= Kerlinger3>{{cite journal|doi=10.2307/1368844}}</ref> More circumstance evidence shows a lack of starvation in the eastern part of North America as well.<ref>{{cite journal|title=Winter irruptive Snowy Owls (''Bubo scandiacus'') in North America are not starving|doi=10.1139/cjz-2017-0278|url=https://www.researchgate.net/publication/322843463_Winter_irruptive_snowy_owls_in_North_America_are_not_starving}}</ref> There is evidence that some adults are known to return to the same wintering areas in ensuing years, areas which are far south of their breeding range.<ref>{{cite journal|doi=10.29173/bluejay1721}}</ref><ref>{{cite journal|author1=Follen, D. |author2= Luepke, K. |year=1980|title= Snowy Owl recaptures|journal= Inland Bird Banding |volume=52|pages= 60}}</ref> At Logan Airport, most snowy owls that are seen appear to be in good condition.<ref name= Holt/> Of 71 dead snowy owls found in winter in the northern Great Plains, 86% died from assorted [[Major trauma|traumas]], including [[Roadkill|collisions]] with automobiles and other, usually manmade, objects as well as [[electrocution]]s and [[Culling|shootings]]. Only 14% of the 71 deaths were due to apparent starving. Data showed some owls appeared to incur injuries but healed and survived.<ref name= Kerlinger3/> More evidence was found in wintering snowy owls in New York of [[Bone healing|healed fractures]], though some may require surgery to recover.<ref>{{cite journal|pmid=30204018|title=Successful Management of Open, Contaminated Metacarpal Fractures in an Adult Snowy Owl (''Bubo scandiacus'') With a Minimal Type II External Skeletal Fixator}}</ref> 537 wintering birds in Saskatchewan were studied based on [[Fatty acid metabolism|fat reserves]], which were superior in females over males and adults over juveniles; while 31% of females lacked fat reserves, at least 45% of males found starving or in a state of infirmity were males and 63% turned into [[Wildlife rehabilitation]] centres were also males.<ref name= Chang/> In British Columbia, of 177 snowy owl deaths, of owls to die, only a small percentage were due to natural causes, such as assumed starvation at 13% and 12% were "found dead".<ref name= Campbell/> 1 fledgling on Fetlar dead due to [[pneumonia]] and ''[[Staphylococcus]]'' while a second died from ''[[Aspergillosis]]''.<ref name= Robinson/> Evidence shows that in Utqiaġvik during exceptionally prolonged rains (i.e. 2 to 3 days), nest-departed young in Utqiaġvik were vulnerable to starvation, leading to [[hypothermia]] and pneumonia.<ref name= Holt/> Due to their natural history, the snowy owl may be effected more severely by [[Parasitism|blood parasitism]] than other raptors, due to lowered [[Immunity (medical)|immunity]].<ref>{{cite journal|pmid=29517448|title=Clinical effect of hemoparasite infections in snowy owls (''Bubo scandiacus'')}}</ref> Conversely, they appear to have lower levels of ectoparasites like [[Mallophaga|chewing lice]] than in other large owls per large samples from [[Manitoba]]. The snowy owls averaged about 3.9 chewing lice per host against 7.5 for great grey owls and 10.5 for great horned owls.<ref>{{cite journal|doi=10.4039/tce.2019.42|title=Infestation parameters for chewing lice (Phthiraptera: Amblycera, Ischnocera) infesting owls (Aves: Strigidae, Tytonidae) in Manitoba, Canada}}</ref> ==Status== -This species presence and numbers is dependent on amount of food available. In "lemming years", snowy owls can appear to be quite abundant in habitat.<ref name= Konig/> Numbers of snowy owls are difficult to estimate even within studies that take place over decades due to the nomadic nature of adults.<ref name= Holt/> The population of [[Scandinavia]] has long been perceived as very small and [[Ephemerality|ephemeral]] with Finland holding 0–100 pairs; Norway holding 1–20 pairs and Sweden holding 1–50 pairs.<ref name= Holt/><ref name= Jacobsen/><ref>Väisänen, R. A., Lammi, E., & Koskimies, P. (1998). ''Distribution, numbers and population changes of Finnish breeding birds''. Otava, Helsinki, Finland.</ref><ref name= Saurola>{{cite journal|doi=10.5253/078.097.0411}}</ref> A low breeding population within [[European Russia]] has been estimated to hold 1,300–4,500 pairs and Greenland to have 500–1,000 pairs.<ref>BirdLife International (2015). ''European Red List of Birds''. Office for Official Publications of the European Communities, Luxembourg</ref><ref>{{cite journal|doi=10.3312/jyio.44.1|title=Cross-species amplification of microsatellite markers in the Great Horned Owl ''Bubo virginianus'', Short-eared Owl ''Asio flammeus'' and Snowy Owl ''B. scandiacus'' for use in population genetics, individual identification and parentage studies}}</ref> Other than northern part of the American continent, a majority of the snowy owl's breeding range is in northern Russia, but overall estimates are not known.<ref name= Holt/><ref>Stepanyan, L.S. (1990). ''Konspekt ornitologicheskoi fauny SSSR. [Conspectus of the Ornithological Fauna of the USSR]''. Nauka, Moscow. (In Russian with English summary.).</ref> An exact count of 4,871 individuals were seen on surveys between the [[Indigirka River|Indigirka]] and [[Kolyma river]]s.<ref name= Potapov/> The numbers estimated by Partners in Flight and other authors by the 2000s was that North America held about 72,500 snowy owls, about 30% of which were juveniles.<ref>Rich, T. D., Beardmore, C. J. Berlanga, H., Blancher, P. J., Bradstreet, M. S. W., Butcher, G. S., Demarest, D. W., Dunn, E. H., Hunter, W. C., Iñigo-Elias, E. E., Kennedy, J. A., Martell, A. M.. Panjabi, A. O., Pashley, D. N., Rosenberg, K. V., Rustay, C. M., Wendt, J. S. & Will, T. C. (2004). ''Partners in Flight North American Landbird Conservation Plan''. Cornell Lab of Ornithology, Ithaca, NY, USA.</ref><ref>{{cite journal|doi=10.2193/0091-7648(2006)34[1392:EOFHOW]2.0.CO;2}}</ref> The Canadian population of snowy owls was estimated at 10,000–30,000 (in the 1990s) or even to 50,000–100,000 individuals, perhaps improbably.<ref>{{cite journal|author=Kirk, D. A., Hussell D. & Dunn, E. |year=1995|title=Raptor population status and trends in Canada|journal= Bird Trends|volume= 4|pages= 2–9}}</ref><ref>Reding-License, A. A. (2015). Harfang des neiges (''Bubo scandiacus''). Government of Canada.</ref><ref>American Ornithologists' Union (1998). ''Check-list of North American Birds, 7th edition''. American Ornithologists' Union, Washington, DC, USA.</ref> Within Canada, the population on [[Banks Island]] was once claimed at up to 15,000–25,000 in productive years and in [[Queen Elizabeth Islands]] at about 932 individuals.<ref name= Manning/><ref>Miller, F. L. (1987). ''Snowy Owl numbers on twelve Queen Elizabeth Islands, Canadian High Arctic''. Journal of Raptor Research 21 (4): 153–157.</ref> Alaska is the only state with breeding snowy owls but has probably quite a bit fewer breeding owls than does Canada.<ref>Alaska Department of Fish and Game. State of Alaska special status species 2011.</ref> Furthermore, the Partners in Flight and the [[IUCN]] estimated that the world population was roughly 200,000–290,000 individuals as recently as the 2000s.<ref>PIFSC. ''Partners in Flight Science Committee (2013)''. Population estimates database (Version 2.0) 2013. Available from http://rmbo.org/pifpopestimates.</ref><ref>BirdLife International. ''Nyctea Scandiaca''. 2006 IUCN Red List of Threatened Species (2004). Available from http://www.iucnredlist.org.</ref><ref>Burton, J. A. (1973). ''Owls of the world''. New York: E. P. Dutton.</ref> However, in the 2010s, it has been discovered that all prior estimates were extremely excessive and that more precise numbers could be estimated with better surveying, [[Phylogeography|phylogeographic data]] and more insights into the owl's free-wheeling wanderings.<ref name="iucn status 19 November 2021" /><ref name= Holt/> It is now believed that there are only 14,000–28,000 mature breeding pairs of snowy owls in the world.<ref name= Holt/><ref name= Marthinsen/> During lemming declines, the number of nesting females may drop down to as low as 1,700 worldwide, a dangerously low number, and the number of snowy owls worldwide is less than 10% of what it was once thought to be.<ref name= Holt/><ref name= Marthinsen/><ref>{{cite journal|doi=10.2307/1527}}</ref> Due to the small and rapidly declining population, the snowy was uplisted in 2017 to being a [[vulnerable species]] by the [[IUCN]].<ref name="iucn status 19 November 2021" /> A 52% decline has been inferred for the North American population since the 1960s with another even more drastic estimate placing the decline from 1970 to 2014 at 64%.<ref>Berlanga, H., Kennedy, J. A., Rich, T. D., Arizmendi, M. C., Beardmore, C. J., Blancher, P. J., Butcher, G. S., Couturier, A. R., Dayer, A. A., Demarest, D. W., Easton, W. E., Gustafson, M., Iñigo-Elias, E., Krebs, E. A., Panjabi, A. O., Rodriguez Contreras, V., Rosenberg, K. V., Ruth, J. M., Santana Castellón, E., Vidal, R. Ma. & Will, T. (2010). ''Saving our shared birds: Partners in Flight tri-national vision for landbird conservation''. Ithaca: Cornell Laboratory of Ornithology.</ref><ref>Rosenberg, K. V., Blancher, P. J., Stanton, J. C., & Panjabi, A. O. (2017). ''Use of North American Breeding Bird Survey data in avian conservation assessments''. The Condor: Ornithological Applications, 119(3), 594–606.</ref> Trends are harder to delineate in Scandinavia but a similar downward trend is thought to be occurring.<ref name= Holt/><ref name= Jacobsen/><ref name= Saurola/> +This species presence and numbers is dependent on amount of food available. In "lemming years", snowy owls can appear to be quite abundant in habitat.<ref name= Konig/> Numbers of snowy owls are difficult to estimate even within studies that take place over decades due to the nomadic nature of adults.<ref name= Holt/> The population of [[Scandinavia]] has long been perceived as very small and [[Ephemerality|ephemeral]] with Finland holding 0–100 pairs; Norway holding 1–20 pairs and Sweden holding 1–50 pairs.<ref name= Holt/><ref name= Saurola>{{cite journal|doi=10.5253/078.097.0411}}</ref> A low breeding population within [[European Russia]] has been estimated to hold 1,300–4,500 pairs and Greenland to have 500–1,000 pairs.<ref>BirdLife International (2015). ''European Red List of Birds''. Office for Official Publications of the European Communities, Luxembourg</ref><ref>{{cite journal|doi=10.3312/jyio.44.1|title=Cross-species amplification of microsatellite markers in the Great Horned Owl ''Bubo virginianus'', Short-eared Owl ''Asio flammeus'' and Snowy Owl ''B. scandiacus'' for use in population genetics, individual identification and parentage studies}}</ref> Other than northern part of the American continent, a majority of the snowy owl's breeding range is in northern Russia, but overall estimates are not known.<ref name= Holt/><ref>Stepanyan, L.S. (1990). ''Konspekt ornitologicheskoi fauny SSSR. [Conspectus of the Ornithological Fauna of the USSR]''. Nauka, Moscow. (In Russian with English summary.).</ref> An exact count of 4,871 individuals were seen on surveys between the [[Indigirka River|Indigirka]] and [[Kolyma river]]s.<ref name= Potapov/> The numbers estimated by Partners in Flight and other authors by the 2000s was that North America held about 72,500 snowy owls, about 30% of which were juveniles.<ref>Rich, T. D., Beardmore, C. J. Berlanga, H., Blancher, P. J., Bradstreet, M. S. W., Butcher, G. S., Demarest, D. W., Dunn, E. H., Hunter, W. C., Iñigo-Elias, E. E., Kennedy, J. A., Martell, A. M.. Panjabi, A. O., Pashley, D. N., Rosenberg, K. V., Rustay, C. M., Wendt, J. S. & Will, T. C. (2004). ''Partners in Flight North American Landbird Conservation Plan''. Cornell Lab of Ornithology, Ithaca, NY, USA.</ref><ref>{{cite journal|doi=10.2193/0091-7648(2006)34[1392:EOFHOW]2.0.CO;2}}</ref> The Canadian population of snowy owls was estimated at 10,000–30,000 (in the 1990s) or even to 50,000–100,000 individuals, perhaps improbably.<ref>{{cite journal|author=Kirk, D. A., Hussell D. & Dunn, E. |year=1995|title=Raptor population status and trends in Canada|journal= Bird Trends|volume= 4|pages= 2–9}}</ref><ref>Reding-License, A. A. (2015). Harfang des neiges (''Bubo scandiacus''). Government of Canada.</ref><ref>American Ornithologists' Union (1998). ''Check-list of North American Birds, 7th edition''. American Ornithologists' Union, Washington, DC, USA.</ref> Within Canada, the population on [[Banks Island]] was once claimed at up to 15,000–25,000 in productive years and in [[Queen Elizabeth Islands]] at about 932 individuals.<ref name= Manning/><ref>Miller, F. L. (1987). ''Snowy Owl numbers on twelve Queen Elizabeth Islands, Canadian High Arctic''. Journal of Raptor Research 21 (4): 153–157.</ref> Alaska is the only state with breeding snowy owls but has probably quite a bit fewer breeding owls than does Canada.<ref>Alaska Department of Fish and Game. State of Alaska special status species 2011.</ref> Furthermore, the Partners in Flight and the [[IUCN]] estimated that the world population was roughly 200,000–290,000 individuals as recently as the 2000s.<ref>PIFSC. ''Partners in Flight Science Committee (2013)''. Population estimates database (Version 2.0) 2013. Available from http://rmbo.org/pifpopestimates.</ref><ref>BirdLife International. ''Nyctea Scandiaca''. 2006 IUCN Red List of Threatened Species (2004). Available from http://www.iucnredlist.org.</ref><ref>Burton, J. A. (1973). ''Owls of the world''. New York: E. P. Dutton.</ref> However, in the 2010s, it has been discovered that all prior estimates were extremely excessive and that more precise numbers could be estimated with better surveying, [[Phylogeography|phylogeographic data]] and more insights into the owl's free-wheeling wanderings.<ref name="iucn status 19 November 2021" /><ref name= Holt/> It is now believed that there are only 14,000–28,000 mature breeding pairs of snowy owls in the world.<ref name= Holt/><ref name= Marthinsen/> During lemming declines, the number of nesting females may drop down to as low as 1,700 worldwide, a dangerously low number, and the number of snowy owls worldwide is less than 10% of what it was once thought to be.<ref name= Holt/><ref name= Marthinsen/><ref name=chitty>{{cite journal|doi=10.2307/1527}}</ref> Due to the small and rapidly declining population, the snowy was uplisted in 2017 to being a [[vulnerable species]] by the [[IUCN]].<ref name="iucn status 19 November 2021" /> A 52% decline has been inferred for the North American population since the 1960s with another even more drastic estimate placing the decline from 1970 to 2014 at 64%.<ref>{{cite journal|doi=10.1650/CONDOR-17-57.1}}</ref> Trends are harder to delineate in Scandinavia but a similar downward trend is thought to be occurring.<ref name= Holt/><ref name= Saurola/> ===Anthropogenic mortality and persecution=== @@ -165,7 +165,7 @@ Of 438 band encounters in the USG banding laboratory, almost all causes of death that could be determined, whether intentional or not, were correlated with human interference.<ref name= Holt/> 34.2% or 150 were dead due to unknown causes, 11.9% were shot, 7.1% were hit by automobiles, 5.5% were found dead or injured on highways, 3.9% were collision from towers or wires, 2.7% were in animal traps, 2.1% in airplane [[birdstrike]]s, 0.6% were [[Wire obstacle|entangled]] while the remaining 33.3% recovered injured due to assorted or unknown causes.<ref name= Holt/> Snowy owls are endangered by heavy airport usage resulting in [[birdstrike]]s. Many such collisions are known in Canada and likely also in [[Siberia]] and Mongolia .<ref name= Catling>{{cite journal|author=Catling, P. M. |year=1973|title=Food of snowy owls wintering in southern Ontario, with particular reference to the snowy owl hazard to aircraft|journal=Ontario field biol|volume= 7|pages= 41–45}}</ref><ref>{{cite journal|doi=10.2307/1367598}}</ref> Despite their danger to planes, no human fatalities have been recorded in collisions with this species.<ref>Blokpoel, H. (1976). ''Bird hazards to aircraft: problems and prevention of bird/aircraft collisions''. Clarke Irwin;[Ottawa]: Canadian Wildlife Service, Environment Canada: Pub. Centre, Supply and Services Canada.</ref> Snowy owls are always far outnumbered in Canadian airports in winter by [[short-eared owl]]s.<ref name= Voous/> However, relative to its scarcity, the snowy accounts for a very large balance of the birdstrikes recorded at American airports due to the attractiveness of the habitat, accounting for 4.6% of 2456 recorded collisions (the barn owl is the most frequently involved in birdstrikes).<ref name= Linnell>{{cite journal|doi=10.3356/JRR-17-64.1}}</ref> The species is locally vulnerable to [[pesticide]]s.<ref name= Konig/> The placement of buildings in the Utqiaġvik is now thought to have displaced some snowy owls.<ref name= Holt3/> In Norway, potential sources of disturbance near the nests include tourism, [[recreation]], [[Reindeer herding|reindeer husbandry]], [[Traffic|motorized traffic]], dogs, photographers, ornithologists and scientists.<ref name= Heggoy/> Some biologist have expressed concern that [[Telemetry|radio-tagging]] of snowy owls may cause some unclear detrimental effect on snowy owls but little evidence is known if they actually make the owls more susceptible to death.<ref>{{cite journal|doi=10.15845/on.v40i0.1309|title=Effects of satellite transmitters on survival in Snowy Owls ''Bubo scandiacus''}}</ref> -Snowy owls can be quite wary, as they are not infrequently hunted by [[Circumpolar peoples]].<ref name= Voous/> Historically, the snowy owl was one of the most persecuted owl species.<ref name= Holt/> In the irruption of 1876–77, an estimated 500 snowy owls were shot, with similar numbers in 1889–90 and an estimated 500–1,000 killed in [[Ontario]] alone during 1901–02 invasion and about 800 killed in the 1905–06 invasion.<ref name= Bent/> Indigenous people of the Arctic historically killed snowy owls as food but now many communities in northern Alaska are fairly modernized, therefore biologists feel that the permitted killing of snowy owls by the indigenous is outdated.<ref name= Holt/><ref>{{cite journal|url=https://brooklynworks.brooklaw.edu/bjil/vol30/iss2/6/|author=Bakalar, E. M. |year=2004|title=Subsistence Whaling in the Native Village of Barrow: Bringing Autonomy to Native Alaskans Outside the International Whaling Commission|journal= Brook. J. Int'l L.|volume= 30|pages= 601}}</ref> The consumption of snowy owls by humans has been proven as far back as ancient cave deposits in France and elsewhere, and they have even been considered as one of the most frequent food species for early humans.<ref>{{cite journal|url=https://www.researchgate.net/publication/285483173_La_chasse_aux_oiseaux_pendant_la_Prehistoire|author=Mourer-Chauviré, C. |year=1979|title=La chasse aux oiseaux pendant la Préhistoire|journal= La Recherche|volume= 106|issue=10|pages= 1202–1210}}</ref><ref>{{cite journal|doi=10.1016/J.QUAINT.2015.11.146|title=Hunting fast-moving, low-turnover small game: The status of the snowy owl (''Bubo scandiacus'') in the Magdalenian}}</ref> They do not shun developed areas especially with old field that hold rodents and, due to lack of human experience, can be extremely tame and unable to escape armed humans.<ref name= Voous/> In British Columbia, of 177 snowy owl deaths, the most often diagnosed cause of death was shootings at 25%, often well after legal protection of the species.<ref name= Campbell/> The number [[Poaching|poached]] snowy owls in Ontario is opined to be unusually high considering their scarcity.<ref name= Desmarchelier>Desmarchelier, M., Santamaria-Bouvier, A., Fitzgérald, G., & Lair, S. (2010). ''Mortality and morbidity associated with gunshot in raptorial birds from the province of Quebec: 1986 to 2007''. The Canadian Veterinary Journal, 51(1), 70.</ref> While the species was once otherwise killed as food and then later shot out of resentment for perceived threats against domestic and favored game stock, the reasoning behind ongoing shooting of snowy owls into the 21st century is not well-understood.<ref name= Holt/><ref name= Dufresne/><ref name= Desmarchelier/> Siberian snowy owls are frequently victim to [[Bait (luring substance)|baited]] [[Trapping|fox traps]], with possibly up to around 300 killed in a year based upon very rough estimates.<ref>{{cite journal|author=Ellis, D. H. & D. G. Smith|year=1993|title=Preliminary report of extensive Gyrfalcon and Snowy Owl mortality in northern Siberia|journal= Raptor-Link |volume=1 |issue=2|pages=3–4}}</ref> [[Warfarin]] poisoning in use as [[rodenticide]]s are known to kill some wintering snowy owls, including up to six at Logan Airport alone.<ref name= Campbell/><ref name= Smith/><ref>{{cite journal|author=Stone, W. B., Okoniewski, J. C. & Stedelin, J. R. |year=1999|pmid=10231745|title=Poisoning of wildlife with anticoagulant rodenticides in New York|journal= Journal of Wildlife Diseases |volume=35|pages=187–193}}</ref> [[Mercury (element)|Mercury]] concentrations, most likely through [[bioaccumulation]], have been detected in snowy owls in the [[Aleutian Islands]] but it is not known whether fatal [[mercury poisoning]] has occurred.<ref>{{cite journal|doi=10.1016/j.marpolbul.2014.02.034}}</ref> [[Polychlorinated biphenyl|PCB]]s may have killed some snowy owls in concentration.<ref name= Heggoy/> Some airports have advocated and instituted the practice of shooting owls to avoid birdstrikes but successful [[Wildlife translocation|translocation]] is possible and preferred given the species protected status.<ref name= Holt/><ref name= Smith/><ref name= Linnell/> +Snowy owls can be quite wary, as they are not infrequently hunted by [[Circumpolar peoples]].<ref name= Voous/> Historically, the snowy owl was one of the most persecuted owl species.<ref name= Holt/> In the irruption of 1876–77, an estimated 500 snowy owls were shot, with similar numbers in 1889–90 and an estimated 500–1,000 killed in [[Ontario]] alone during 1901–02 invasion and about 800 killed in the 1905–06 invasion.<ref name= Bent/> Indigenous people of the Arctic historically killed snowy owls as food but now many communities in northern Alaska are fairly modernized, therefore biologists feel that the permitted killing of snowy owls by the indigenous is outdated.<ref name= Holt/><ref>{{cite journal|url=https://brooklynworks.brooklaw.edu/bjil/vol30/iss2/6/|author=Bakalar, E. M. |year=2004|title=Subsistence Whaling in the Native Village of Barrow: Bringing Autonomy to Native Alaskans Outside the International Whaling Commission|journal= Brook. J. Int'l L.|volume= 30|pages= 601}}</ref> The consumption of snowy owls by humans has been proven as far back as ancient cave deposits in France and elsewhere, and they have even been considered as one of the most frequent food species for early humans.<ref>{{cite journal|url=https://www.researchgate.net/publication/285483173_La_chasse_aux_oiseaux_pendant_la_Prehistoire|author=Mourer-Chauviré, C. |year=1979|title=La chasse aux oiseaux pendant la Préhistoire|journal= La Recherche|volume= 106|issue=10|pages= 1202–1210}}</ref><ref>{{cite journal|doi=10.1016/J.QUAINT.2015.11.146|title=Hunting fast-moving, low-turnover small game: The status of the snowy owl (''Bubo scandiacus'') in the Magdalenian}}</ref> They do not shun developed areas especially with old field that hold rodents and, due to lack of human experience, can be extremely tame and unable to escape armed humans.<ref name= Voous/> In British Columbia, of 177 snowy owl deaths, the most often diagnosed cause of death was shootings at 25%, often well after legal protection of the species.<ref name= Campbell/> The number [[Poaching|poached]] snowy owls in Ontario is opined to be unusually high considering their scarcity.<ref name= Desmarchelier>Desmarchelier, M., Santamaria-Bouvier, A., Fitzgérald, G., & Lair, S. (2010). ''Mortality and morbidity associated with gunshot in raptorial birds from the province of Quebec: 1986 to 2007''. The Canadian Veterinary Journal, 51(1), 70.</ref> While the species was once otherwise killed as food and then later shot out of resentment for perceived threats against domestic and favored game stock, the reasoning behind ongoing shooting of snowy owls into the 21st century is not well-understood.<ref name= Holt/><ref name= Dufresne/><ref name= Desmarchelier/> Siberian snowy owls are frequently victim to [[Bait (luring substance)|baited]] [[Trapping|fox traps]], with possibly up to around 300 killed in a year based upon very rough estimates.<ref>{{cite journal|author=Ellis, D. H. & D. G. Smith|year=1993|title=Preliminary report of extensive Gyrfalcon and Snowy Owl mortality in northern Siberia|journal= Raptor-Link |volume=1 |issue=2|pages=3–4}}</ref> [[Warfarin]] poisoning in use as [[rodenticide]]s are known to kill some wintering snowy owls, including up to six at Logan Airport alone.<ref name= Campbell/><ref>{{cite journal|author=Stone, W. B., Okoniewski, J. C. & Stedelin, J. R. |year=1999|pmid=10231745|title=Poisoning of wildlife with anticoagulant rodenticides in New York|journal= Journal of Wildlife Diseases |volume=35|pages=187–193}}</ref> [[Mercury (element)|Mercury]] concentrations, most likely through [[bioaccumulation]], have been detected in snowy owls in the [[Aleutian Islands]] but it is not known whether fatal [[mercury poisoning]] has occurred.<ref>{{cite journal|doi=10.1016/j.marpolbul.2014.02.034}}</ref> [[Polychlorinated biphenyl|PCB]]s may have killed some snowy owls in concentration.<ref name= Heggoy/> Some airports have advocated and instituted the practice of shooting owls to avoid birdstrikes but successful [[Wildlife translocation|translocation]] is possible and preferred given the species protected status.<ref name= Holt/><ref name= Linnell/> [[File:Stare Down Snowy (94026869).jpeg|thumb|right|A potential high risk of electrocution exists for snowy owls in winter.]] -[[Global warming|Climate change]] is now widely perceived to perhaps the primary driver of the snowy owl's decline. As temperatures continue to rise, abiotic factors such as increased rain and reduced snow are likely to effect lemming populations and, in turn, snowy owls. These and potentially many other issues (possibly including modifying migrating behavior, vegetation composition, increased insect, disease and parasite activities, risk of [[hyperthermia]]) are a matter of concern.<ref name="iucn status 19 November 2021" /><ref name= Holt/><ref name= Heggoy/><ref name= ACIA>ACIA. (2004). ''Impacts of a warming climate: Arctic climate impact assessment''. Cambridge: Cambridge University Press.</ref><ref>Inouye, D. W. (2019). "Climate change in other taxa". ''Effects of Climate Change on Birds'', p. 257. {{ISBN|9780198824268}}</ref> Additionally, reduction of sea ice, which snowy owls are now known to rely extensively on, as a result of warming climates, impacts could be significant.<ref name="iucn status 19 November 2021" /><ref name= Holt/><ref name= Marine/> The effect of [[climate change]] was essentially confirmed in northern Greenland where a perhaps irrevocable collapse of the lemming population was observed. From 1998 to 2000, the lemming numbers appeared to have quickly declined. The number of lemmings per hectare (ha) is less than one-fifth of what it once was in Greenland (i.e. from 12 lemmings per ha to less than 2 per ha at peak). This is almost certainly correlated with a 98% decline in owl productivity as well as that of the local [[Stoat|stoats]] (the [[long-tailed jaeger]] and [[Arctic fox]]es, though previously thought to be almost as reliant on lemmings, seem to be more loosely coupled and more generalized and did not decline as much).<ref name= Schmidt>{{cite journal|pmid=22977153}}</ref><ref>{{cite journal|doi=10.4080/gpcw.2011.0113}}</ref> The amount of lemming mounds is much less than it once in northern Greenland and any variety of [[population cycle]] has been apparently abandoned by what remains of the lemmings.<ref name= Schmidt/> +[[Global warming|Climate change]] is now widely perceived to perhaps the primary driver of the snowy owl's decline. As temperatures continue to rise, abiotic factors such as increased rain and reduced snow are likely to effect lemming populations and, in turn, snowy owls. These and potentially many other issues (possibly including modifying migrating behavior, vegetation composition, increased insect, disease and parasite activities, risk of [[hyperthermia]]) are a matter of concern.<ref name="iucn status 19 November 2021" /><ref name= Holt/><ref name= Heggoy/><ref>Inouye, D. W. (2019). "Climate change in other taxa". ''Effects of Climate Change on Birds'', p. 257. {{ISBN|9780198824268}}</ref> Additionally, reduction of sea ice, which snowy owls are now known to rely extensively on, as a result of warming climates, impacts could be significant.<ref name="iucn status 19 November 2021" /><ref name= Holt/><ref name= Marine/> The effect of [[climate change]] was essentially confirmed in northern Greenland where a perhaps irrevocable collapse of the lemming population was observed. From 1998 to 2000, the lemming numbers appeared to have quickly declined. The number of lemmings per hectare (ha) is less than one-fifth of what it once was in Greenland (i.e. from 12 lemmings per ha to less than 2 per ha at peak). This is almost certainly correlated with a 98% decline in owl productivity as well as that of the local [[Stoat|stoats]] (the [[long-tailed jaeger]] and [[Arctic fox]]es, though previously thought to be almost as reliant on lemmings, seem to be more loosely coupled and more generalized and did not decline as much).<ref name= Schmidt>{{cite journal|pmid=22977153}}</ref><ref>{{cite journal|doi=10.4080/gpcw.2011.0113}}</ref> The amount of lemming mounds is much less than it once in northern Greenland and any variety of [[population cycle]] has been apparently abandoned by what remains of the lemmings.<ref name= Schmidt/> ==In popular culture== '
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[ 0 => 'Snowy owls may be active to some extent at both day, from dawn to dusk, and night.<ref name= Konig/> Snowy owls have been seen to be active even during the very brief winter daytime in the northern winter.<ref name= Voous/> During the Arctic summer, snowy owls may tend to peak in activity during the twilight that is the darkest time available given the lack of full nightfall.<ref name= Voous/><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/nab/v027n01/p00011-p00012.pdf|author=Young, C.M. |year=1973|title=The Snowy Owl migration of 1971–72 in the Sudbury region of Ontario|journal= American Birds |volume=27|issue=1|pages= 11–12}}</ref><ref name=shields>{{cite journal|doi=10.2307/3536292}}</ref> Reportedly, the peak time of activity during summer is between 9:00&nbsp;pm and 3:00&nbsp;am in Norway.<ref name= Hagen>Hagen, Y. (1960). ''The Snowy Owl on Hardangervidda in the Summer of 1959''. Papers of The Norwegian State Game Research. 2, No. 7.</ref> The peak time of activity for those owls that once nested on Fetlar was reported between 10:00 and 11:00&nbsp;pm.<ref name= Tulloch>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V61/V61_N03/V61_N03_P119_132_A019.pdf|author=Tulloch, R. J. |year=1968|title=Snowy Owls breeding in Shetland in 1967|journal= British Birds|volume= 61|pages=119–132}}</ref> According to one authority, the least active times are at noon and midnight.<ref name= Watson/> As days become longer near autumn in [[Utqiaġvik, Alaska|Utqiaġvik]], the snowy owls in the tundra become more active around nightfall and can often be seen resting during the day, especially if it is raining.<ref name=shields/> During winter in [[Alberta]], snowy owls were tracked in the daytime, despite being also active at night (as they were deemed too difficult to track). In the study, they were most active during 8:00–10:00&nbsp;am and 4:00–6:00&nbsp;pm and often rested mostly from 10:00&nbsp;am to 4:00&nbsp;pm. The owls were perched for 98% of observed daylight and seemed to time their activity to peak times for rodents.<ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/jfo/v060n01/p0020-p0029.pdf|author1=Boxall, P. C. |author2= Lein, M. R. |year=1989|title=Time budgets and activity of wintering Snowy Owls|journal= Journal of Field Ornithology |volume=60 |issue=1|pages= 20–29}}</ref> The variation of activity is probably in correspondence with their primary prey, the [[lemming]]s, and like them, the snowy owl may be considered [[Cathemerality|cathermal]].<ref name= Konig/><ref name= Voous/><ref name="National Geographic">{{cite web|title=Snowy Owl (Nyctea Scandia)|url=http://animals.nationalgeographic.com/animals/birds/snowy-owl/|website=animals.nationalgeographic.com|publisher=National Geographic|date=11 November 2010}}</ref> This species can withstand extremely cold temperatures, having been recorded in temperatures as low as minus 62.5 [[Celsius|degrees Celsius]] with no obvious discomfort and also withstood a 5-hour exposure to minus 93 degrees Celsius but may have struggled with oxygen consumption by the end of this period. The snowy owl has perhaps the second lowest [[thermal conduction]] to the plumage on average of any bird after only the [[Adelie penguin]] (''Pygoscelis adeliae'') and rivals the best insulated mammals, such as [[Dall sheep]] (''Ovis dalli'') and [[Arctic fox]], as the best insulated polar creature.<ref name= Voous/><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/condor/v057n06/p0362-p0365.pdf|author=Irving, L. |title=Nocturnal decline in the temperature of birds in cold weather|doi=10.2307/1364794}}</ref> Presumably as many as 7 rodents would need to be eaten daily to survive an extremely cold winter's day.<ref name= Voous/> Adults and young both have been seen to shelter behind rocks to shield themselves from particularly harsh winds or storms.<ref name= Holt/> Snowy owls often spending a majority of time on the ground, perched mostly on a slight rise of elevation.<ref name= Konig/> It has been interpreted from the morphology of their skeletal structure (i.e. their short, broad legs) that snowy owls are not well-suited to perching extensively in trees or rocks and prefer a flat surface to sit upon.<ref name= Potapov/> However, they may perch more so in winter though do so only mainly when hunting, at times on [[hummock]]s, [[Fence]]posts, [[telegraph pole]]s by roads, [[Radio tower|radio]] and [[transmission tower]]s, [[Hay]]stacks, [[chimney]]s and the roofs of houses and large buildings.<ref name= Voous/> Rocks may be used as perches at times in all seasons.<ref name= Voous/> Though often relatively sluggish owls, like most related species, they are capable of sudden dashing movements in various contexts.<ref name= Potapov/> Snowy owls can walk and run quite quickly, using outstretched wings for balance if necessary.<ref name= Konig/> This owl flies with fairly rowing wingbeats, occasionally interrupted by gliding on stretched wings. The flight is fairly buoyant for a ''Bubo'' owl.<ref name= Konig/><ref name= Holt/> When displaying, the male may engage in an undulating flight with interspersed wingbeats and gliding in a slight dihedral, finally dropping rather vertically to the ground.<ref name= Konig/> They are capable for swimming but do not usually do so. Some seen to be swimming were previously injured but young have been seen to swim into water to escape predators if they cannot fly yet. They will also drink when unfrozen water is available.<ref name= Holt/><ref name= Tulloch/><ref>Mebs, T. & Scherzinger, W. (2000). ''Snowy Owl''. In: ''Die eulen Europa: biolgie, kennzeichen, bestande'', edited by T. Mebs and W. Scherzinger, 167–183. Stuttgart: Franckh-Kosmos Verlags-Gmbh and Co.</ref> Snowy owl mothers have been observed to [[Preening (bird)|preen]] their young in the wild, while pairs in captivity have been observed to allopreen.<ref name= Watson/> In the period leading up to breeding, snowy owls switched regularly between searching (for nesting grounds) and loafing, often searching less when snow cover was less extensive.<ref>Therrien, J. F., Pinaud, D., Gauthier, G., Lecomte, N., Bildstein, K. L., & Bety, J. (2015). ''Pre-breeding prospecting behaviour of snowy owls'' (data from Therrien et al. 2015)-reference-data.</ref> ', 1 => 'It is fair to say that the snowy owl is a partial, if fairly irregular, [[Bird migration|migrant]], having a very broad but patchy wintering range.<ref name= Konig/> 1st year birds tend to disperse farther south in winter than older owls with males wintering usually somewhat more to the south than females of equivalent ages, adult females often wintering the farthest north.<ref name= Voous/><ref name= Scandinavica>Kerlinger, P. & Lein, M.R. (1986). ''Differences in winter range among age-sex classes of Snowy Owls Nyctea scandiaca in North America''. Ornis Scandinavica. 17(1): 1–17.</ref> The snowy owl likely covers more ground than almost any other owl in movements but many complex individual variations are known in movements, and they often do not take the traditional north–south direction that might be assumed.<ref name= Holt/> Migratory movements appear to be somewhat more common in America than in Asia.<ref name= Konig/> A study of wintering owls in the [[Kola Peninsula]] determined that the mean date of arrival of owls was 10 November with a departure date of 13 April, covering an average of {{convert|991|km|mi|abbr=on}} during the course of the wintering period and clustering where [[Ptarmigan|prey]] was more concentrated.<ref>Øien, I. J., Aarvak, T., Jacobsen, K. O., & Solheim, R. (2018). ''Satellite Telemetry Uncovers Important Wintering Areas for Snowy Owls On the Kola Peninsula, Northwestern Russia''. Орнитология, 42, 42–49.</ref> Some variety of movements recorded each autumn and snowy owls winter annually in plains of [[Siberia]] and Mongolia and [[prairie]]s and [[marsh]]lands of Canada.<ref name= Voous/> The [[Great Plains]] area of southern Canada host wintering snowy owls about 2 to 10 times more frequently than other areas of the continent.<ref name= Holt/> Some weak correlation has made with individuals having some level of fealty to certain wintering sites.<ref>Oeming, A. F. (1957). ''Notes on the Barred Owl and the Snowy Owl in Alberta''. Blue Jay 15:153–156.</ref><ref>Follen, D. & Luepke, K. (1980). ''Snowy Owl recaptures''. Inland Bird Banding 52: 60.</ref> Wintering snowy owls, a total of 419, recorded in [[Duluth, Minnesota]] from 1974 to 2012 would occur in larger numbers in years where [[Brown rat|rats]] were more plentiful. The amount of individual returns among 43 Duluth-wintering owls was fairly low in subsequent winters (8 for 1 year, a small handful in the next few years, and 9 in non-consecutive years).<ref name= Holt/> Sometimes surveys appeared to reveal hundreds of wintering snowy owls on coastal sea ice during an irruptive year.<ref name= Voous/><ref name= Marine/> Three siblings that hatched in same nest in [[Cambridge Bay]] were recovered in drastically different spots at least a year later: one in eastern [[Ontario]], one in [[Hudson Bay]] and one in [[Sakhalin Island]].<ref name= Parmelee/> A nestling banded in [[Sogn og Fjordane|Hordaland]] was recovered {{convert|1380|km|mi|abbr=on}} to the northeast in [[Finnmark]].<ref name= Voous/> In the [[Logan Airport]], 17 of 452 owls were recorded to return, eleven the following year, three 2 years later, and then singles variously 6, 10 and 16 years later.<ref name= Holt/> A banded female from Utqiaġvik was recorded to migrate over {{convert|1928|km|mi|abbr=on}} along seacoast down to Russia, returning over {{convert|1528|km|mi|abbr=on}} and covering at least {{convert|3476|km|mi|abbr=on}} in total. Another banded young female from Utqiaġvik went to the same Russian areas, returned to Utqiaġvik and then onto [[Victoria Island (Canada)|Victoria Island]], but did appear to breed, while another also covered a similar route but ended up nesting on [[Banks Island]]. Another female migrated to the [[Canada–United States border]], then moved back to the [[Gulf of Alaska]], then to winter in the same border areas and then finally to both Banks and Victoria Island.<ref name= Holt/> Snowy owls from the Canadian Arctic were monitored to have covered an average of {{convert|1100|km|mi|abbr=on}} in one autumn then covered an average of {{convert|2900|km|mi|abbr=on}} a year later.<ref name= Therrien2>Therrien, J.-F., Fitzgerald, G., Gauthier G. & Bêty, J. (2011). ''Diet-tissue discrimination factors of carbon and nitrogen stable isotopes in blood of Snowy Owl (Bubo scandiacus)''. Canadian Journal of Zoology 89 (4): 343–347.</ref> In late winter, owls from the same area were found to have covered a mean of {{convert|4093|km|mi|abbr=on}} of ground in the tundra and spent a mean of 108 days, apparently searching for a suitable nesting situation the entire time.<ref>Therrien, J.-F. , Gauthier, G., Pinaud, D. & Bêty, J. (2014). ''Irruptive movements and breeding dispersal of Snowy Owls: a specialized predator exploiting a pulsed resource''. Journal of Avian Biology. 45(6): 536–544.</ref>', 2 => 'In no fewer than 24 winters between 1882 and 1988, large numbers have occurred in Canada and the United States. These were [[Irruptive growth|irruption]] years.<ref name= Voous/> Record breeding irruptive years were recorded in the winters of 2011–2012 and 2014–2015.<ref name= Holt/> In the 1940s, it was calculated that the mean gape in time between large irruptions was 3.9 years.<ref name= Gross1/> Southbound movements as such are much more conspicuous after peak vole years, once thought to be separated by periods of around 3–7 years.<ref name= Voous/><ref>{{cite journal|author=Snyder, L. L. |year=1943|title=The Snowy Owl migration of 1941–42|journal= Wilson Bulletin |volume=55 |issue=1|pages=8–10|jstor=4157203|url=https://sora.unm.edu/sites/default/files/journals/wilson/v055n01/p0008-p0010.pdf}}</ref><ref>{{cite journal|doi=10.2307/4079810}}</ref><ref name=chitty/> However, more extensive research has weakened the argument that irruptions are entirely food-based and the data indicates that irruptive movements are far from predictable. This is because a statewide survey in Alaska found no statewide synchrony in lemming numbers. Therefore, rather than decline of lemmings, it is the successful productivity of several pairs that plays the role, resulting in a large number of young owls that then irrupt. However, the snowy owls cannot breed in high numbers unless lemmings are widely available on the tundra.<ref name= Holt/><ref name= Kerlinger2/><ref name= Gross/><ref>Pitelka, F. A. & Batzli, G. O. (1993). ''Distribution, abundance, and habitat use by lemmings on the north slope of Alaska''. In: ''The biology of lemmings'', edited by N. C. Stenseth and R. A. Ims, 213–236. London: Academic Press.</ref><ref name="Krebs">Krebs, C. J. (1993). ''Are lemmings large Microtus or small reindeer? A review of lemming cycles after 25 years and future recommendations for future work''. In: ''The biology of lemmings'', edited by N. C. Stenseth and R. Ims, 247–260. London: Academic Press for the Linnean Society of London.</ref> This connection of irruptions to high years of productivity was confirmed in a study by Robillard et al. (2016).<ref>{{cite journal|pmid=26920901|doi=10.1007/s00442-016-3588-3}}</ref> About 90% of the snowy owls seen in irruptive years from 1991 to 2016 that were ageable were identified as juveniles.<ref name= Santonja/>', 3 => 'Snowy owls may hunt at nearly at any time of the day or night, but may not attempt to do so during particularly severe weather.<ref name= Holt/> During the [[summer solstice]], the owls appear to hunt during "theoretical nightfall".<ref name= Holt/> [[Night-vision device]]s have allowed biologists to observe that snowy owls hunt quite often during the extended nighttime during the northern winter.<ref name= Potapov/><ref name= Holt/> Prey are both taken and eaten on the ground.<ref name= Konig/> Snowy owls, like other carnivorous birds, often swallow their small prey whole.<ref name= Konig/> Strong stomach juices digest the flesh, while the indigestible bones, teeth, fur, and feathers are compacted into oval pellets that the bird regurgitates 18 to 24 hours after feeding. Regurgitation often takes place at regular perches, where dozens of pellets may be found. Biologists frequently examine these pellets to determine the quantity and types of prey the birds have eaten. When large prey are eaten in small pieces, pellets will not be produced.<ref>[http://www.owlpages.com/owls.php?genus=Bubo&species=scandiacus Snowy Owl — ''Bubo scandiacus'', formerly ''Nyctea scandiaca'']. owlpages.com</ref> Larger prey is often torn apart, sometimes include removal of the head, with the large muscles, such as the [[humerus]] or [[Thorax|breast]], typically eaten first.<ref name= Holt/> The scattering of remains that results from the increment feeding on larger prey is thought to result in under-identification of them compared to smaller prey items.<ref>{{cite journal|title=A taphonomic investigation of small vertebrate accumulations produced by the snowy owl (''Bubo scandiacus'') and its implications for fossil studies|doi=10.1016/j.palaeo.2018.10.018}}</ref> The aptitude for hunting by day, hunting from the ground and hunting in almost always completely open and treeless areas are the primary ways in which the snowy owl differs in hunting from other ''Bubo'' owls. Otherwise, the hunting habits are similar.<ref name= Holt/><ref name= Johnsgard>[[Paul Johnsgard|Johnsgard, P. A.]] (1988). [https://digitalcommons.unl.edu/johnsgard/46/ ''North American owls: biology and natural history'']. Smithsonian Institution.</ref> It is thought, due to their less refined hearing compared to other owls, prey is usually perceived via vision and movement.<ref name= Voous/><ref name= Holt/> Experiments indicate that snowy owls can detect prey from as far as {{convert|1.6|km|mi|abbr=on}} away. Snowy owls generally use a rise or, occasionally, a perch while hunting.<ref name= Konig/> 88% of observed 34 hunts in Utqiaġvik were undertaken from an elevated watch-site (56% mounds or rises, 37% [[telephone pole]]s).<ref name= Holt/> Their hunting style may recall that of [[Buteo|buzzard]]s, with the hunting owl sitting rather low and perching immobile for a long spell.<ref name= Hume/> Although their usual flight is a slow, deliberate downbeat on the broad, fingered wings, when prey is detected from their perch, flight may undertaken with a sudden, surprisingly quick accelerated style with interspersed wing beats.<ref name= Hume/><ref>{{cite journal|author=Hohn, E. O. |year=1973|title=Winter hunting of Snowy Owls in farmland|journal= Canadian Field-Naturalist|volume= 87 |issue=4|pages= 468–469}}</ref> In Utqiaġvik, snowy owls may most frequently engage in a brief pursuit hunting style.<ref name= Holt/> In high winds capable of keeping their bulk aloft, snowy owls may too engage in a brief [[Levitation|hovering]] flight before dropping onto prey.<ref name= Watson/> When hunting fish, apparently, some snowy owls will hover in a style reminiscent of the [[osprey]] (''Pandion haliaetus''), although in at least one other case a snowy owl was observed to capture fish by lying on its belly upon a rock by a fishing hole.<ref name= Audubon>Audubon, J. J. (1840). ''The Birds of America''. Dover Publications, Inc., New York, NY, USA.</ref> A dashing stoop or pounce down onto their prey, ending in a high-impact "wallop", is fairly commonly recorded.<ref name= Holt/><ref name= Hume/> Another common technique is the "sweep", wherein they fly by and grasp the prey while continuing to fly.<ref name= Holt/><ref>{{cite journal|author=Dancey, H.E. |year=1983|title=Winter foraging habits of a Snowy Owl|journal= Indiana Audubon Quarterly|volume= 61|issue=4|pages= 136–144}}</ref> In winter, snowy owls have been shown to be able to "snow plunge" to capture prey in the [[Subnivean climate|subnivean zone]], under at least {{convert|20|cm|in|abbr=on}} of snow. Perhaps least frequently, snowy owls may pursue their on foot, in doing so never taking wing.<ref name= Holt/> Snowy owls have been known to capture [[Bird migration|night-migrating]] [[passerine]]s and [[shorebird]]s, sometimes perhaps on the wing, as well as large and/or [[Bird of prey|potentially dangerous]] birds that were caught in air by snowy owls during daylight.<ref name= Holt/> On the wing pursuits against other various other carnivorous birds are sometimes undertaken as well to [[Kleptoparasitism|kleptoparasitize]] the prey caught by the other birds.<ref name= Holt/><ref>Duffy, D. C., Beehler B. & Haas, W. (1976). ''Snowy Owl steals prey from Marsh Hawk''. Auk 93 (4): 839–840.</ref> Few variations of hunting technique were observed in winter observations from [[Alberta]], almost all of the hunts being with the sit-and-wait method (also known as still-hunts). Adult females in Alberta had a considerably better hunting rate than juvenile females.<ref name= Boxall2>{{cite journal|doi=10.14430/arctic2326|title=Feeding ecology of Snowy Owls (''Nyctea scandiaca'') wintering in S. Alberta}}</ref> Much as in Alberta, in [[Syracuse, New York]], 90% of 51 hunts were still-hunting, with the sweep variant used after perch departure in 31% of hunts and the pounce method in 45% of hunts. The Syracuse-wintering owls used tall perches, a mixture of manmade objects and trees of around {{convert|6|m|ft|abbr=on}} high, in nearly 61% of hunts, while nearly 14% were from low perches (i.e. fence-posts, snow banks and scrap piles) about half as high as the tall perches and started from a ground position nearly 10% of the time.<ref name= Winter>Winter, R. E. (2016). ''Hunting Behaviors and Foraging Success of Winter Irruptive Snowy Owls in New York''. SUNY College of Environmental Science and Forestry, Thesis.</ref> In Sweden, males hunted from a perch more so than did females and adults both focused on significantly smaller prey (small [[mammal]]s) and may have had more success hunting than juvenile snowy owls.<ref name= Lind/> Some snowy owls can survive a fast for up to about 40 days off of [[Fatty acid metabolism|fat reserves]].<ref name= Hume/> These owls were found to have extremely thick [[Subcutaneous tissue|subcutaneous fat deposits]] of around {{convert|19|to|22|mm|in|abbr=on}} and it is likely owls that overwinter in the Arctic rely heavily on these to survive during this scarce time, in combination with lethargic, energy-conserving behavior.', 4 => 'Data from the [[Logan Airport]] in over 6,000 pellets shows that meadow vole and brown rat predominated the diet in the area, supplanted by assorted birds both small and large.<ref name= Holt/> [[American black duck]]s were primarily taken among bird species with other birds taken here including relatively large and diverse species [[Canada geese]] (''Branta canadensis''), brants, [[American herring gull]]s (''Larus argentatus''), [[double-crested cormorant]] (''Phalacrocorax auritus''), [[great blue heron]] (''Ardea herodias''), in addition to some formidable mammals such as [[Cat|house cat]], [[American mink]] (''Mustela vision''), and [[striped skunk]] (''Mephitis mephitis'').<ref name= Holt/> Given the large size of some of this prey, it can be projected that the snowy owl can kill adult prey of around twice their own weight (i.e. geese, cats, skunks, etc.).<ref name= Holt/> Other large prey is sometimes taken by snowy owls, all roughly within the {{convert|2|to|5|kg|lb|abbr=on}} weight range often include adults of large [[leporid]]s such as [[Arctic hare]] (''Lepus arcticus''),<ref name= Holt/> [[Alaskan hare]] (''Lepus othus''),<ref>Best, T. L., & Henry, T. H. (1994). ''Lepus othus''. Mammalian Species, (458), 1–5.</ref> [[mountain hare]]<ref>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V54/V54_N08/V54_N08_P307_320_A051.pdf|author=Bergman, G. |year=1961|title=The food of birds of prey and owls in Fenno-Scandia|journal= British Birds|volume= 54|issue=8|pages= 307–320}}</ref> and [[white-tailed jackrabbit]]s (''Lepus townsendii'').<ref name= Boxall2/> As well as several species of geese, probable cygnets of [[Tundra swan|Bewick's swan]]s (''Cygnus columbianus bewickii'')<ref>Nagy, S., Petkov, N., Rees, E., Solokha, A., Hilton, G., Beekman, J., & Nolet, B. (2012). [https://www.unep-aewa.org/en/publication/international-single-species-action-plan-conservation-northwest-european-population International single species action plan for the conservation of the northwest European population of Bewick's Swan (''Cygnus columbianus bewickii'')]. Wetlands International and The Wildfowl & Wetlands Trust (WWT), AEWA Technical Series, (44).</ref> as well as adults of the following: [[western capercaillie]] (''Tetrao urogallus'') (of both sexes),<ref>Gilyazov, A. V. (2005). ''Snowy Owl Nyctea scandiaca Linnaeus, 1758''. Red-data Book of the Murmansk Region. Murmansk: Murmansk book publishers: 316—318. [in Russian].</ref> [[greater sage-grouse]] (''Centrocercus urophasianus'')<ref>{{cite journal|doi=10.1002/jwmg.21168}}</ref> and [[yellow-billed loon]]s (''Gavia adamsii'').<ref>Uher-Koch, B. D., M. R. North, and J. A. Schmutz (2020). Yellow-billed Loon (''Gavia adamsii''), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.</ref> At the other end of the scale, the snowy owl has been known to take birds down to size of {{convert|19.5|g|oz|abbr=on}} [[dark-eyed junco]]s (''Junco hyemalis'') and mammals down the size of {{convert|8.1|g|oz|abbr=on}} [[common shrew]]s (''Sorex araneus'').<ref name= Hakala/><ref name= Young/><ref name= CRC1>Dunning, Jr., J. B. (1993). ''CRC handbook of avian body masses''. CRC Press, Boca Raton, FL.</ref> Fish are rarely taken anywhere but the snowy owl has been known to prey upon [[Arctic char]] (''Salvelinus alpinus'') and [[lake trout]] (''Salvelinus namaycush'').<ref name= Voous/><ref name= Gross/><ref name= Bailey>Bailey, A. M. (1948). ''Birds of Arctic Alaska''. Colorado Mus. Nat. Hist., Popular Ser., 8.</ref>', 5 => 'When it goes south to winter outside of the Arctic, the snowy owl has a potential to interact with a number of additional predators.<ref name= Voous/> By necessity, it shares its wintertime diverse prey with a number of formidable predators.<ref name= Voous/><ref name= Holt/> These are known to include their cousins, the [[great horned owl]] and the [[Eurasian eagle-owl]]. They are relieved of heavy competition from the related species by differing temporal activity, i.e. being more likely to actively hunt in daytime, and by habitat, using rather more open (quite often nearly treeless) habitats than them.<ref name= Potapov/><ref name= Voous/> During a study of wintering snowy owls in [[Saskatchewan]], the authors indicated that the snowy owls may avoid areas inhabited and defended by great horned owls. Although they usually occurred here outside of a {{convert|800|m|ft|abbr=on}} radius of central great horned owl ranges, they did not avoid the {{convert|1600|m|ft|abbr=on}} radius and different habitat usage may be a dictating factor.<ref name= Chang2>Chang, A. M. (2017). ''Habitat use, movement patterns, and body condition of male and female Snowy Owls (Bubo scandiacus) in winter'' (Doctoral dissertation, University of Saskatchewan).</ref> Given their mildly slighter size, it is unlikely that great horned owls (unlike the larger eagle-owl) would regularly dominate snowy owls in interactions and either species may give way to other depending on the size and disposition of the owls involved.<ref name= Potapov/><ref name= Voous/> Little study has been undertaken into the [[Trophic level|trophic competition]] of snowy owls with other predators during winter and, due to their scarcity, few predators are likely to expel much energy on competitive interactions with them, although many other predators will engage in anti-predator [[Mobbing (animal behavior)|mobbing]] of snowy owls.<ref name= Voous/><ref name= Holt/> Largely in winter, snowy owls have been the victim of a number of larger avian predators, though attacks are likely to be singular and rare.<ref name= Voous/><ref name= Holt/> Instances of predation on snowy owls are known to have been committed several times in winter only by [[Eurasian eagle-owl]]s.<ref name= Mikkola3>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V69/V69_N04/V69_N04_P144_154_A030.pdf|author=Mikkola, H. |year=1976|title=Owls killing and killed by other owls and raptors in Europe|journal= British Birds|volume= 69|pages= 144–154}}</ref> Additionally, [[golden eagle]]s (''Aquila chrysaetos'') have been known to prey on snowy owls as well as all northern [[sea eagle]]s: the [[Bald eagle|bald]] (''Haliaeetus leucocephalus''), [[White-tailed eagle|white-tailed]] (''Haliaeetus albicilla'') and [[Steller's sea eagle]]s (''Haliaeetus pelagicus'').<ref name= Holt/><ref name= Campbell/><ref>{{cite journal|author=Johnson, M.J. |year=1995|title=Bald Eagle predation on Snowy Owl|journal= Loon|volume= 67|issue=2|pages=107}}</ref> Snowy owls are also sometimes killed by birds that are mobbing them. In one instance, a [[peregrine falcon]] killed a snowy owl in a stoop after the owl had itself killed a fledgling falcon.<ref name= Bent/><ref name= Bailey/><ref>Nelson, E. W. (1887). ''Birds of Alaska'', p. 35-222. In H. W. Henshaw [ed.], Report upon natural history collections made in Alaska between the years 1877 and 188 1. No. III Arctic Series, Signal Service, U.S. Army, Government Printing Office,-Washington, DC.</ref> Anecdotal report indicate predation by [[gyrfalcon]]s (on snowy owls of unknown age and condition) but it was possibly also an act of mobbing.<ref name= Heggoy>Heggøy, O., & Øien, I. J. (2014). [https://www.birdlife.no/innhold/bilder/2014/01/29/2586/nof_rapport_12014.pdf ''Conservation status of birds of prey and owls in Norway'']. NOF/BirdLife Norway-Report, 1, 1–129.</ref> In another, a huge [[Flock (birds)|throng]] of [[Arctic tern]]s (''Sterna paradisaea'') relentlessly swarmed and attacked a snowy owl until it meet its demise.<ref>Meinertzhagen, R. (1959). ''Pirates and Predators: The piratical and predatory habits of birds''. Oliver & Boyd.</ref>', 6 => 'Almost certainly more often than being victim of other predators, snowy owls are known to dominate, kill and feed on a large diversity of other predators.<ref name= Voous/><ref name= Mikkola3/> Snowy owls, much like other ''Bubo'' owls, will opportunistically kill other birds of prey and predators. Although they will readily plunder the nests of other raptorial birds given the opportunity, most predations are on full-grown raptorial birds during winter due to the scarcity of raptor nests in the open tundra.<ref name= Voous/> In addition, most competing predators of the Arctic, excepting the very large mammals, are probably vulnerable to a hungry snowy owl.<ref name= Voous/><ref name= Holt/> In data from the [[Logan Airport]] alone over different winters, the snowy owls were observed to have preyed upon an impressive diversity of other raptorial birds: [[rough-legged buzzard]]s, [[American kestrel]]s (''Falco sparverius''), [[peregrine falcon]]s, [[barn owl]]s, other snowy owls, [[barred owl]]s (''Strix varia''), [[northern saw-whet owl]]s (''Aegolius acadicus'') and [[short-eared owl]]s. While owls are likely encountered during corresponding hunting times, it is likely that the swift falcons are usually ambushed at night (much as other ''Bubo'' owls will do).<ref name= Holt/> In both the tundra and the wintering ground, there are several accounts of predation by snowy owls on short-eared owls.<ref name= Potapov/><ref name= Mikkola3/><ref>{{cite journal|doi=10.2307/1368028}}</ref> In addition, snowy owls have been known to prey on [[northern harrier]]s,<ref name= Holt/> [[northern goshawk]]s (''Accipiter gentilis'')<ref name= Voous/> and [[gyrfalcon]]s.<ref name= Voous/><ref name= Mikkola3/> In a few cases, both juvenile and adult [[Arctic fox]]es have been known to fall prey to snowy owls.<ref name= Parker/><ref name= Stenkewitz/><ref name= Krechmar/><ref name="Gilg">{{cite journal|doi=10.1111/j.2006.0030-1299.14125.x}}</ref><ref>{{cite journal|title=''Alopex lagopus''|doi=10.1644/0.713.1}}</ref> A wintering snowy owl in [[Saskatchewan]] was observed to have preyed on an adult [[red fox]] (''Vulpes vulpes''). Predation by snowy owls on red foxes was also reported in the [[Irkutsky District]] of Russia. With an adult weight around {{convert|6|kg|lb|abbr=on}} (and far from defenseless), red fox may be the largest known prey known for snowy owls.<ref name= Maleev/><ref>{{cite journal|doi=10.29173/bluejay3979}}</ref> Besides aforementioned predation on domestic cats and skunks, several members of the [[weasel]] family, both small and relatively large, are known to be opportunistically hunted by snowy owls.<ref name= Potapov/><ref name= Voous/><ref name= Holt/><ref name= Hakala/><ref>{{cite journal|doi=10.2307/3565424}}</ref> As a result of its potential predator status, the snowy owl is frequently mobbed at all times of the year by other predatory birds, including fierce dive-bombing by several of the northern falcons on the wintering grounds, including even by the relatively tiny but fierce and very agile [[Merlin (bird)|merlin]] (''Falco columbarius''). The much bulkier snowy owls cannot match the speed and flight ability of a falcon, ai may be almost relentlessly tormented by some birds such as peregrines.<ref name= Voous/><ref name= Mikkola3/><ref>{{cite journal|doi=10.29173/bluejay208}}</ref>', 7 => 'In Utqiaġvik, of 239 recorded breeding attempts, 232 were monogamous, the other 7 [[Bigamy|social bigamy]].<ref name= Holt/> On [[Baffin Island]], 1 male bred with 2 females and sired 11 total fledged young.<ref name= Watson/> Another case of bigamy was reported in Norway where the 2 females bred to one male were {{convert|1.3|km|mi|abbr=on}} apart in nest site location.<ref name= Hagen/> On Feltar from 1967 to 1975, a male breed with two females, 1 younger and was possibly his own [[Incest|daughter]]. In the Feltar males first time breeding with both females, he did not bring food to the younger female. However, when older female disappeared the following year, the male and younger female producing 4 young, but disappeared the subsequent year altogether in 1975.<ref name= Robinson/> There are also unconfirmed cases of [[polyandry]], with 1 female being fed by 2 males. Snowy owls can breed once per year but when food is scarce many do not even attempt to breed.<ref name= Konig/><ref name= Voous/> Despite frequent wandering in search of food, they generally adhere more so than to a strict breeding season than [[short-eared owl]]s nesting in the tundra.<ref name= Voous/> 9 radio-tagged female snowy owls about [[Bylot Island]] were tracked to study how pre-laying snow cover effects their searching behavior for breeding area. These tracked females searched an average of 36 days and covered an average of {{convert|1251|km|mi|abbr=on}}. It is thought that the male and female mutually find an attractive breeding spot independently and converge.<ref>{{cite journal|doi=10.1186/s40462-015-0028-7}}</ref> The breeding territory normally averages about {{convert|2.6|km2|sqmi|abbr=on}} as in both [[Baffin Island]] and [[Ellesmere Island]] but varies in accordance to abundance of food and density of owls.<ref name= Konig/><ref name= Watson/> Nesting territories average at Baffin island in the range of {{convert|8|to|10|km2|sqmi|abbr=on}} during poor lemming years.<ref name= Watson/> Nesting territories may up to {{convert|22|km2|sqmi|abbr=on}} on [[Southampton Island]] and had a mean distance of {{convert|4.5|km|mi|abbr=on}} between active nests.<ref name= Sutton1/> In Utqiaġvik, nesting pairs can vary from none to at least 7 and the territories average {{convert|5|to|10|km2|sqmi|abbr=on}}, with mean nest distances of {{convert|1.5|to|6|km|mi|abbr=on}}.<ref name= Pitelka/> In the Norwegian highlands, nesting occurs only at times of plenty distances of {{convert|1.2|to|3.7|km|mi|abbr=on}} between nests, averaging {{convert|2.1|km|mi|abbr=on}}.<ref name= Hagen/> Males marks territory with singing and display flights and likely always initiates.<ref name= Watson/> During the display, he engages in exaggerated wing beats with a shallow undulating and bouncy courtship flight with wings held in a [[Dihedral (aeronautics)|dihedral]]. He often drops to the ground but then flies again to only glide gently back down. Overall, the flight is somewhat reminiscent of the flight of a [[moth]].<ref name= Watson/><ref name= Pitelka/><ref name= Tulloch/><ref name= Robinson/> Females will answer her mate with her song during courtship.<ref name= Konig/> While courting, the male often also carries a lemming in his bill, then bows with cocked tail, similarly as in related owls (seldom displaying some other prey like [[snow bunting]]s). He then flaps his wings open in an emphatic manner, with the ground display being relatively brief (about 5 minutes). The female may possibly refuse to breed if ritual not performed.<ref name= Watson/><ref name= Taylor/> A possible courtship was engaged in by a male in southern Saskatchewan when a female was sighted.<ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v094n01/p0079-p0081.pdf|author1=Boxall, P. C. |author2= Lein, M. R. |year=1982|title=Possible courtship behavior of Snowy Owls in winter|journal= Wilson Bulletin|volume= 94|pages=79–81}}</ref> On Southampton Island, at least 20 males observed in late May in a "lemming year".<ref name= Voous/><ref name= Sutton1/> Nesting territory defense displays, not highly different from courtship displays, includes undulating flight and stiffly raised wings with bouts of exaggerated, delayed wing beats, looking like enormous white moths exposing their white wings under the sun.<ref name= Taylor/> At times, competing males will interlock claws in mid-air.<ref name= Voous/> Territorial and nuptial displays are followed by a ground display by the male with the wings arched up in an "angel" posture, visible for well over a mile.<ref name= Voous/>', 8 => 'Most individuals arrive at the nest site by April or May with a few overwintering arctic exceptions.<ref name= Murie/><ref name= Marine/><ref name= Pitelka2/> Males advertises potential nest sites to his mate by scratching the ground and spreading his wings over it.<ref name= Konig/> The nest is usually a shallow depression on a windswept eminence in the open tundra. There seems to be a variety of qualifiers for appropriate nest sites. The nest site is typically snow-free and dry relative to the surrounding environment, usually with a good view of the surrounding landscape. The nest may be made of [[ridge]]s, [[Mound|elevated mound]]s, high [[polygon]]s, [[hummock]]s, hills, man-made mounds and occasionally [[Outcrop|rocky outcrops]]. If covered with vegetation, taller plants that may obstruct view are plucked away sometimes.<ref name= Konig/><ref name= Voous/><ref name= Watson/><ref name= Pitelka2/><ref name= Holt3>{{cite journal|doi=10.5253/078.097.0422}}</ref> The nest sites are often long-established and naturally created by the freeze-thaw process of the tundra.<ref name= Voous/><ref name= Holt/> [[Bar (river morphology)|Gravel bars]] may be used as well.<ref name= Potapov/> The female may take the most active role in the nest's condition of any owl species.<ref name= Holt/><ref name= Mikkola/> No owl build their own nests but female snowy owls take about three days constructing a scrape, digging with her claws and rotating until a fairly circular bowl is formed. She will still not construct or add foreign materials to the nest (despite some circumstantial evidence of moss and grass from outside the nest mound being found).<ref name= Holt/><ref name= Murie/><ref name= Tulloch/> In two separate cases in Utqiaġvik, two separate females dug out a second scrape to the side and below the main nests and appeared to have called all chicks to the more secluded nest to ride out severe weather until the skies cleared.<ref name= Holt/> The Utqiaġvik nest scrapes averaged {{convert|47.7|x|44|cm|in|abbr=on}} in 91 with a mean depth of {{convert|9.8|cm|in|abbr=on}} while the scrapes were smaller in [[Hooper Bay]], reportedly {{convert|25|to|33|cm|in|abbr=on}} diameter and {{convert|4|to|9|cm|in|abbr=on}} in depth.<ref name= Murie/><ref name= Holt3/> Occasionally, in the lower tundra, snowy owls may too use old nests of [[rough-legged buzzard]]s as well as abandoned [[eagle]] nests.<ref name= Voous/> Unlike other northerly breeding raptorial birds, the snowy owl is not known to nest on cliffs and the like, so do not enter into direct competition with eagles, falcons, ravens or other ''Bubo'' owls when nesting to the relative south.<ref name= Voous/> The area of nest mound often has a relatively rich plant life which attract the lemmings, which may tunnel right under and around the owl's nest.<ref name= Voous/> [[Goose|Geese]], ducks and [[shorebird]]s of several species known to gain incidental protection by nesting close to snowy owls. Conversely, the snowy owls will sometimes kill and eat both young and adults of these birds, which implies a trade-off in the benefits.<ref name= Parmelee/><ref name= Murie/><ref name= Robinson/><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v109n03/p0449-p0461.pdf|author=Tremblay, J. P., Gauthier, G., Lepage, D., & Desrochers, A. |year=1997|title=Factors affecting nesting success in greater snow geese: Effects of habitat and association with snowy owls|journal= The Wilson Bulletin|pages= 449–461|volume=109|issue=3|jstor=4163840}}</ref><ref>{{cite journal|doi=10.1139/z96-210}}</ref><ref>{{cite journal|doi=10.1007/BF02465456|title=How do Brent Geese (''Branta b. bernicla'') cope with evil}}</ref><ref>Smith, P. A. (2003). ''Factors affecting nest site selection and reproductive success of tundra nesting shorebirds'' (Doctoral dissertation, University of British Columbia).</ref>', 9 => 'Food is brought to the nest by males and surplus food is stored nearby.<ref name= Konig/> Females in breeding season often develop a very extensive [[brood patch]] which in this species is a fairly enormous, high vascularized featherless area of pink belly skin.<ref name= Voous/><ref name= Parmelee/> Incubation lasts 31.8–33 days (unconfirmed and possibly dubious reports from as little as 27 to as much as 38-day incubations).<ref name= Konig/><ref name= Murie/><ref name= Robinson/><ref name= Schaanning/> The female alone broods the young, often while simultaneously incubating still unhatched eggs.<ref name= Konig/><ref name= Holt/> Sometimes older chicks incidentally brood their younger siblings and females may shelter the young under her wings during inclement weather.<ref name= Parmelee/><ref name= Watson/> When first feeding the young, the female may dismantle prey to feed the young only the softer body parts then gradually ramping up the size of proportions until they eat a whole prey item.<ref name= Watson/> Aggressive encounters with parent snowy owls are said to be "genuinely dangerous" and one resource claimed the snowy owl to be the bird species with the most formidable nest defense displays towards humans.<ref name= Voous/><ref name= Bent/><ref>Couzens, D. (2008). ''Extreme Birds: The World's Most Extraordinary and Bizarre Birds''. Firefly Books.</ref> The usual response to sighted humans near the nest is mild but continued approach begins to increasingly irritate the parents.<ref name= Holt/> At times, humans are forcefully dive-bombed upon, while other potential threats are dealt with in a “forward-threat” where the male walks towards the intruders, engaging in impressive feather-raising and fanning out of half-spread wings until they run forward and slash with both their feet and bill.<ref name= Voous/><ref name= Bent/><ref name= Watson/><ref name= Sutton1/><ref name= Parmelee/> Fairly serious injuries have been sustained in the worst of snowy owl defensive attacks, including cranial trauma, requiring researchers to make the long trek back to medical care, although human fatalities are not known.<ref name= Sutton/> Snowy owl parents have been seen to aggressively attacked glaucous gulls, arctic fox and dogs in breeding ground in Utqiaġvik.<ref name= Holt/> Non-predatory animals like [[Reindeer|caribou]] in Utqiaġvik and sheep (''Ovis aries'') in Fetlar are attacked as well, possibly to avoid potential trampling of the eggs or the young.<ref name= Parmelee/><ref name= Tulloch/> Males are said to do the majority of nest defense but the female will also often become involved as well.<ref name= Holt/> Analysis showed in [[Lapland, Sweden]], that females in nest defense against people engaged in vocal displays (warning and mewing calls) and that males did not engage in mewing but did engage in most hooting calls, many warning calls and almost all physical attacks.<ref name= Wiklund>{{cite journal|title=Nest defence and evolution of reversed sexual size dimorphism in Snowy Owls ''Nyctea scandiaca''|doi=10.2307/3676252}}</ref> In other instances, [[distraction display]]s are engaged in against predators, with a "broken-wing act" including high, thin squeals interspersed with weird squeaks, often taking flight only to quickly fall from the sky and imitate a struggle.<ref name= Voous/><ref>[http://animaldiversity.ummz.umich.edu/site/accounts/information/Nyctea_scandiaca.html ADW: ''Nyctea scandiaca: Information'']. Animaldiversity.ummz.umich.edu. Retrieved on 19 October 2010.</ref> One author recorded a male to draw him about {{convert|2|km|mi|abbr=on}} from the nest before ceasing.<ref name= Parmelee/> 77% of 45 distraction displays in Lapland, Sweden were by females.<ref name= Wiklund/>', 10 => 'Hatching intervals are generally from 1 to 3 days, quite often within 37–45 hours apart.<ref name= Watson/><ref name= Tulloch/> New chicks are [[Altriciality|semi-altricial]] (i.e. typically helpless and blind), initially being white and rather wet but dry by the end of the first day. The weight of 7 hatchlings was {{convert|35|to|55|g|oz|abbr=on}}, with an average of {{convert|46|g|oz|abbr=on}} while 3 were {{convert|44.7|g|oz|abbr=on}}.<ref name= Parmelee/><ref name= Watson/> Due to the pronounced asynchrony of the egg-laying and hatching, the size difference between siblings can be enormous and in some cases when the smallest chick weighs only {{convert|20|to|50|g|oz|abbr=on}}, the biggest chick already has attained a weight of around {{convert|350|to|380|g|oz|abbr=on}}.<ref name= Watson/> When the oldest chick is about 3 weeks, the female will start to hunt as well as the male and both may directly feed the young although in some cases they may not need hunt very much if lemmings are particularly numerous.<ref name= Konig/><ref name= Voous/> [[Hoarding (animal behavior)|Caches]] of lemmings around a nest may include more than 80 lemmings that can support the family.<ref name= Voous/> Unlike many owls, the chicks of snowy owls are not known to behave aggressively toward one another or to engage in [[siblicide]], perhaps in part due to the need for energy conservance.<ref name= Holt/><ref name= Tulloch/> Some cases of [[cannibalism]] of chicks by the family group were thought to be cases where chicks die from other causes.<ref name= Sutton/> When they are about 2 weeks, the chicks may begin to walk around the nest site which they leave by 18–28 days, although they are still unable to fly and may find safety in nooks and crannies of vegetation and rocks usually only about {{convert|1|to|2|m|ft|abbr=on}} from the nest mound, as well as via their parents defense.<ref name= Konig/><ref name= Voous/><ref name= Romero>Romero, L. M., Holt, D. W. Maples M. & Wingfield, J. C.. (2006). ''Corticosterone is not correlated with nest departure in Snowy Owl chicks (Nyctea scandiaca)''. General and Comparative Endocrinology 149 (2): 119–123.</ref> Leaving the nest is thought to likely be an anti-predator strategy.<ref name= Holt/><ref>Holt, D. W. & Leasure, S. M. (1993). ''Short-eared Owl (Asio flammeus)''. In: ''The birds of North America, No. 62'', edited by A. Poole and F. Gill. Washington, DC: Acad. Nat. Sci., Philadelphia, PA; Am. Ornithol. Union.</ref> The male snowy owl may drop fresh prey deliveries directly on the ground near the wandering young.<ref name= Voous/> After about three weeks of age, the young may wander fairly widely, rarely to {{convert|1|km|mi|abbr=on}}, but usually stay within {{convert|500|m|ft|abbr=on}} of the nest mound.<ref name= Watson/><ref name= Tulloch/> Threat postures by young in reaction to researchers were first noticeable at about 20–25 days of age and common at about 28 days and the chicks can be impressively quick and agile-footed.<ref name= Holt/><ref name= Watson/> The first fledgling occurs at around 35–50 days, and by 50–60 days the young can fly well and hunt on their own.<ref name= Konig/><ref name= Voous/> The total care period is for 2–3.5 months, increasing in length with increased size of the brood.<ref name= Konig/><ref name= Parmelee/> Although independence was once thought to be sought by late August or early September but is more likely by late September to October when migration season for the species begins.<ref name= Holt/><ref name= Pitelka2/> The nesting cycle is similar in length to the Arctic short-eared owls and faster than Eurasian eagle-owls by up to 2 months.<ref name= Schrezinger>Schrezinger, W. (1974). ''Zur Ethologie und Jugendentwicklung der Schnee-Eule Nyctea scandiaca nach Beobachtungen in Gefangenschaft''. J. Orn, 115: 8–49.</ref>', 11 => 'Sexual maturity reached the following year but the first breeding is normally at no sooner than the end of the second year of life.<ref name= Konig/> There is little strong evidence of typical age of first breeding but initial breeding by males could be inferred by the plumage of males in Utqiaġvik by plumage. At that stage, which the males were essentially all pure white, most were aged to about 3 to 4 years old.<ref name= Holt/> The snowy owl seems to markedly inconsistent in regard to breeding every year, often taking at least up to two years between attempts and sometimes as much as nearly a decade.<ref name= Potapov/> 7 satellite-marking females in Canada proved that they did breed in consecutive years, with 1 breeding over 3 consecutive years.<ref name= Therrien/> In 23 years at Utqiaġvik, snowys bred in 13 of them.<ref name= Holt/> Nesting success can reach 90–100% in even the largest clutches in high lemming years.<ref name= Voous/> While over the course of 21 years, 260 total nests were recorded in Utqiaġvik. There, from 4–54 nests were recorded annually. The Utqiaġvik nests bore 3 to 10 sized-clutches with a mean of 6 eggs per nest and an annual mean hatching success from 39 to 91%. 31–87% of chicks were able to depart on foot and 48–65% were annually estimated to survive to fledge; elsewhere, 40% survived to fledge.<ref name= Holt/><ref name= Parmelee/> In another set, 97% of observed eggs both hatched and fledged.<ref name= Watson/> In Norway, the fledging success from 10 nests was much lower at about 46%.<ref name= Hagen/> Norwegian data, which previously indicated it to be an almost accidental breeder in northern Norway, indicates that it is a more regular breeder than expected, though. 3 good years were found for snowy owls between 1968 and 2005: 1974 (when there were 12 pairs), 1978 (22 pairs) and 1985 (20 pairs), with 14 additional locations when potential (but not confirmed) breeding has occurred. The main determinable causes of nest failure were deemed to be [[starvation]] and [[Hypothermia|exposure]].<ref name= Holt/> A number of Norwegian and Finnish nests were known to fail due to severe [[black fly]] parasitism.<ref>{{cite journal|doi=10.15845/on.v36i0.394}}</ref>', 12 => 'The snowy owl can live a long life for a bird.<ref name= Holt/> Records show that the oldest snowy owls in captivity can live to 25 to even 30 years of age.<ref name= Konig/><ref name= Holt/><ref>Schenker, A. (1978). Höchsalter europaischer Vögel im Zoologischen Garten Basel. Ornithol. Beob. 75: 96–97.</ref> Typical lifespans probably reach around 10 years in the wild.<ref name= Konig/><ref name= Mikkola/> The longest known lifespan in the wild was one that initially banded (possibly in its first winter) in [[Massachusetts]] and recovered dead in [[Montana]] 23 years and 10-month later.<ref name= Holt/> The annual survival rate for twelve females on [[Bylot Island]] was estimated at around 85–92.3%.<ref>{{cite journal|doi=10.1002/jwmg.414}}</ref> It is often reputed that snowy owls frequently died from starvation, with historical accounts frequently opined they "had to" leave their breeding grounds due to lemming "crashes" but would starve to the south.<ref name= Kerlinger/><ref name= Gross1/><ref name= Zettenberg>{{cite journal|doi=10.1898/NWN07-19.1}}</ref> However, it was proven fairly early on that snowy owls often do survive throughout the winter.<ref name= Bent/> This is reinforced somewhat by small radio-tracking and banding studies of the northern [[Great Plains]] and the intermountain [[valley]]s of the northwestern United States.<ref name= Zettenberg/><ref name= Kerlinger3>{{cite journal|doi=10.2307/1368844}}</ref> More circumstance evidence shows a lack of starvation in the eastern part of North America as well.<ref>{{cite journal|title=Winter irruptive Snowy Owls (''Bubo scandiacus'') in North America are not starving|doi=10.1139/cjz-2017-0278|url=https://www.researchgate.net/publication/322843463_Winter_irruptive_snowy_owls_in_North_America_are_not_starving}}</ref> There is evidence that some adults are known to return to the same wintering areas in ensuing years, areas which are far south of their breeding range.<ref>{{cite journal|doi=10.29173/bluejay1721}}</ref><ref>{{cite journal|author1=Follen, D. |author2= Luepke, K. |year=1980|title= Snowy Owl recaptures|journal= Inland Bird Banding |volume=52|pages= 60}}</ref> At Logan Airport, most snowy owls that are seen appear to be in good condition.<ref name= Holt/> Of 71 dead snowy owls found in winter in the northern Great Plains, 86% died from assorted [[Major trauma|traumas]], including [[Roadkill|collisions]] with automobiles and other, usually manmade, objects as well as [[electrocution]]s and [[Culling|shootings]]. Only 14% of the 71 deaths were due to apparent starving. Data showed some owls appeared to incur injuries but healed and survived.<ref name= Kerlinger3/> More evidence was found in wintering snowy owls in New York of [[Bone healing|healed fractures]], though some may require surgery to recover.<ref>{{cite journal|pmid=30204018|title=Successful Management of Open, Contaminated Metacarpal Fractures in an Adult Snowy Owl (''Bubo scandiacus'') With a Minimal Type II External Skeletal Fixator}}</ref> 537 wintering birds in Saskatchewan were studied based on [[Fatty acid metabolism|fat reserves]], which were superior in females over males and adults over juveniles; while 31% of females lacked fat reserves, at least 45% of males found starving or in a state of infirmity were males and 63% turned into [[Wildlife rehabilitation]] centres were also males.<ref name= Chang/> In British Columbia, of 177 snowy owl deaths, of owls to die, only a small percentage were due to natural causes, such as assumed starvation at 13% and 12% were "found dead".<ref name= Campbell/> 1 fledgling on Fetlar dead due to [[pneumonia]] and ''[[Staphylococcus]]'' while a second died from ''[[Aspergillosis]]''.<ref name= Robinson/> Evidence shows that in Utqiaġvik during exceptionally prolonged rains (i.e. 2 to 3 days), nest-departed young in Utqiaġvik were vulnerable to starvation, leading to [[hypothermia]] and pneumonia.<ref name= Holt/> Due to their natural history, the snowy owl may be effected more severely by [[Parasitism|blood parasitism]] than other raptors, due to lowered [[Immunity (medical)|immunity]].<ref>{{cite journal|pmid=29517448|title=Clinical effect of hemoparasite infections in snowy owls (''Bubo scandiacus'')}}</ref> Conversely, they appear to have lower levels of ectoparasites like [[Mallophaga|chewing lice]] than in other large owls per large samples from [[Manitoba]]. The snowy owls averaged about 3.9 chewing lice per host against 7.5 for great grey owls and 10.5 for great horned owls.<ref>{{cite journal|doi=10.4039/tce.2019.42|title=Infestation parameters for chewing lice (Phthiraptera: Amblycera, Ischnocera) infesting owls (Aves: Strigidae, Tytonidae) in Manitoba, Canada}}</ref>', 13 => 'This species presence and numbers is dependent on amount of food available. In "lemming years", snowy owls can appear to be quite abundant in habitat.<ref name= Konig/> Numbers of snowy owls are difficult to estimate even within studies that take place over decades due to the nomadic nature of adults.<ref name= Holt/> The population of [[Scandinavia]] has long been perceived as very small and [[Ephemerality|ephemeral]] with Finland holding 0–100 pairs; Norway holding 1–20 pairs and Sweden holding 1–50 pairs.<ref name= Holt/><ref name= Saurola>{{cite journal|doi=10.5253/078.097.0411}}</ref> A low breeding population within [[European Russia]] has been estimated to hold 1,300–4,500 pairs and Greenland to have 500–1,000 pairs.<ref>BirdLife International (2015). ''European Red List of Birds''. Office for Official Publications of the European Communities, Luxembourg</ref><ref>{{cite journal|doi=10.3312/jyio.44.1|title=Cross-species amplification of microsatellite markers in the Great Horned Owl ''Bubo virginianus'', Short-eared Owl ''Asio flammeus'' and Snowy Owl ''B. scandiacus'' for use in population genetics, individual identification and parentage studies}}</ref> Other than northern part of the American continent, a majority of the snowy owl's breeding range is in northern Russia, but overall estimates are not known.<ref name= Holt/><ref>Stepanyan, L.S. (1990). ''Konspekt ornitologicheskoi fauny SSSR. [Conspectus of the Ornithological Fauna of the USSR]''. Nauka, Moscow. (In Russian with English summary.).</ref> An exact count of 4,871 individuals were seen on surveys between the [[Indigirka River|Indigirka]] and [[Kolyma river]]s.<ref name= Potapov/> The numbers estimated by Partners in Flight and other authors by the 2000s was that North America held about 72,500 snowy owls, about 30% of which were juveniles.<ref>Rich, T. D., Beardmore, C. J. Berlanga, H., Blancher, P. J., Bradstreet, M. S. W., Butcher, G. S., Demarest, D. W., Dunn, E. H., Hunter, W. C., Iñigo-Elias, E. E., Kennedy, J. A., Martell, A. M.. Panjabi, A. O., Pashley, D. N., Rosenberg, K. V., Rustay, C. M., Wendt, J. S. & Will, T. C. (2004). ''Partners in Flight North American Landbird Conservation Plan''. Cornell Lab of Ornithology, Ithaca, NY, USA.</ref><ref>{{cite journal|doi=10.2193/0091-7648(2006)34[1392:EOFHOW]2.0.CO;2}}</ref> The Canadian population of snowy owls was estimated at 10,000–30,000 (in the 1990s) or even to 50,000–100,000 individuals, perhaps improbably.<ref>{{cite journal|author=Kirk, D. A., Hussell D. & Dunn, E. |year=1995|title=Raptor population status and trends in Canada|journal= Bird Trends|volume= 4|pages= 2–9}}</ref><ref>Reding-License, A. A. (2015). Harfang des neiges (''Bubo scandiacus''). Government of Canada.</ref><ref>American Ornithologists' Union (1998). ''Check-list of North American Birds, 7th edition''. American Ornithologists' Union, Washington, DC, USA.</ref> Within Canada, the population on [[Banks Island]] was once claimed at up to 15,000–25,000 in productive years and in [[Queen Elizabeth Islands]] at about 932 individuals.<ref name= Manning/><ref>Miller, F. L. (1987). ''Snowy Owl numbers on twelve Queen Elizabeth Islands, Canadian High Arctic''. Journal of Raptor Research 21 (4): 153–157.</ref> Alaska is the only state with breeding snowy owls but has probably quite a bit fewer breeding owls than does Canada.<ref>Alaska Department of Fish and Game. State of Alaska special status species 2011.</ref> Furthermore, the Partners in Flight and the [[IUCN]] estimated that the world population was roughly 200,000–290,000 individuals as recently as the 2000s.<ref>PIFSC. ''Partners in Flight Science Committee (2013)''. Population estimates database (Version 2.0) 2013. Available from http://rmbo.org/pifpopestimates.</ref><ref>BirdLife International. ''Nyctea Scandiaca''. 2006 IUCN Red List of Threatened Species (2004). Available from http://www.iucnredlist.org.</ref><ref>Burton, J. A. (1973). ''Owls of the world''. New York: E. P. Dutton.</ref> However, in the 2010s, it has been discovered that all prior estimates were extremely excessive and that more precise numbers could be estimated with better surveying, [[Phylogeography|phylogeographic data]] and more insights into the owl's free-wheeling wanderings.<ref name="iucn status 19 November 2021" /><ref name= Holt/> It is now believed that there are only 14,000–28,000 mature breeding pairs of snowy owls in the world.<ref name= Holt/><ref name= Marthinsen/> During lemming declines, the number of nesting females may drop down to as low as 1,700 worldwide, a dangerously low number, and the number of snowy owls worldwide is less than 10% of what it was once thought to be.<ref name= Holt/><ref name= Marthinsen/><ref name=chitty>{{cite journal|doi=10.2307/1527}}</ref> Due to the small and rapidly declining population, the snowy was uplisted in 2017 to being a [[vulnerable species]] by the [[IUCN]].<ref name="iucn status 19 November 2021" /> A 52% decline has been inferred for the North American population since the 1960s with another even more drastic estimate placing the decline from 1970 to 2014 at 64%.<ref>{{cite journal|doi=10.1650/CONDOR-17-57.1}}</ref> Trends are harder to delineate in Scandinavia but a similar downward trend is thought to be occurring.<ref name= Holt/><ref name= Saurola/>', 14 => 'Snowy owls can be quite wary, as they are not infrequently hunted by [[Circumpolar peoples]].<ref name= Voous/> Historically, the snowy owl was one of the most persecuted owl species.<ref name= Holt/> In the irruption of 1876–77, an estimated 500 snowy owls were shot, with similar numbers in 1889–90 and an estimated 500–1,000 killed in [[Ontario]] alone during 1901–02 invasion and about 800 killed in the 1905–06 invasion.<ref name= Bent/> Indigenous people of the Arctic historically killed snowy owls as food but now many communities in northern Alaska are fairly modernized, therefore biologists feel that the permitted killing of snowy owls by the indigenous is outdated.<ref name= Holt/><ref>{{cite journal|url=https://brooklynworks.brooklaw.edu/bjil/vol30/iss2/6/|author=Bakalar, E. M. |year=2004|title=Subsistence Whaling in the Native Village of Barrow: Bringing Autonomy to Native Alaskans Outside the International Whaling Commission|journal= Brook. J. Int'l L.|volume= 30|pages= 601}}</ref> The consumption of snowy owls by humans has been proven as far back as ancient cave deposits in France and elsewhere, and they have even been considered as one of the most frequent food species for early humans.<ref>{{cite journal|url=https://www.researchgate.net/publication/285483173_La_chasse_aux_oiseaux_pendant_la_Prehistoire|author=Mourer-Chauviré, C. |year=1979|title=La chasse aux oiseaux pendant la Préhistoire|journal= La Recherche|volume= 106|issue=10|pages= 1202–1210}}</ref><ref>{{cite journal|doi=10.1016/J.QUAINT.2015.11.146|title=Hunting fast-moving, low-turnover small game: The status of the snowy owl (''Bubo scandiacus'') in the Magdalenian}}</ref> They do not shun developed areas especially with old field that hold rodents and, due to lack of human experience, can be extremely tame and unable to escape armed humans.<ref name= Voous/> In British Columbia, of 177 snowy owl deaths, the most often diagnosed cause of death was shootings at 25%, often well after legal protection of the species.<ref name= Campbell/> The number [[Poaching|poached]] snowy owls in Ontario is opined to be unusually high considering their scarcity.<ref name= Desmarchelier>Desmarchelier, M., Santamaria-Bouvier, A., Fitzgérald, G., & Lair, S. (2010). ''Mortality and morbidity associated with gunshot in raptorial birds from the province of Quebec: 1986 to 2007''. The Canadian Veterinary Journal, 51(1), 70.</ref> While the species was once otherwise killed as food and then later shot out of resentment for perceived threats against domestic and favored game stock, the reasoning behind ongoing shooting of snowy owls into the 21st century is not well-understood.<ref name= Holt/><ref name= Dufresne/><ref name= Desmarchelier/> Siberian snowy owls are frequently victim to [[Bait (luring substance)|baited]] [[Trapping|fox traps]], with possibly up to around 300 killed in a year based upon very rough estimates.<ref>{{cite journal|author=Ellis, D. H. & D. G. Smith|year=1993|title=Preliminary report of extensive Gyrfalcon and Snowy Owl mortality in northern Siberia|journal= Raptor-Link |volume=1 |issue=2|pages=3–4}}</ref> [[Warfarin]] poisoning in use as [[rodenticide]]s are known to kill some wintering snowy owls, including up to six at Logan Airport alone.<ref name= Campbell/><ref>{{cite journal|author=Stone, W. B., Okoniewski, J. C. & Stedelin, J. R. |year=1999|pmid=10231745|title=Poisoning of wildlife with anticoagulant rodenticides in New York|journal= Journal of Wildlife Diseases |volume=35|pages=187–193}}</ref> [[Mercury (element)|Mercury]] concentrations, most likely through [[bioaccumulation]], have been detected in snowy owls in the [[Aleutian Islands]] but it is not known whether fatal [[mercury poisoning]] has occurred.<ref>{{cite journal|doi=10.1016/j.marpolbul.2014.02.034}}</ref> [[Polychlorinated biphenyl|PCB]]s may have killed some snowy owls in concentration.<ref name= Heggoy/> Some airports have advocated and instituted the practice of shooting owls to avoid birdstrikes but successful [[Wildlife translocation|translocation]] is possible and preferred given the species protected status.<ref name= Holt/><ref name= Linnell/>', 15 => '[[Global warming|Climate change]] is now widely perceived to perhaps the primary driver of the snowy owl's decline. As temperatures continue to rise, abiotic factors such as increased rain and reduced snow are likely to effect lemming populations and, in turn, snowy owls. These and potentially many other issues (possibly including modifying migrating behavior, vegetation composition, increased insect, disease and parasite activities, risk of [[hyperthermia]]) are a matter of concern.<ref name="iucn status 19 November 2021" /><ref name= Holt/><ref name= Heggoy/><ref>Inouye, D. W. (2019). "Climate change in other taxa". ''Effects of Climate Change on Birds'', p. 257. {{ISBN|9780198824268}}</ref> Additionally, reduction of sea ice, which snowy owls are now known to rely extensively on, as a result of warming climates, impacts could be significant.<ref name="iucn status 19 November 2021" /><ref name= Holt/><ref name= Marine/> The effect of [[climate change]] was essentially confirmed in northern Greenland where a perhaps irrevocable collapse of the lemming population was observed. From 1998 to 2000, the lemming numbers appeared to have quickly declined. The number of lemmings per hectare (ha) is less than one-fifth of what it once was in Greenland (i.e. from 12 lemmings per ha to less than 2 per ha at peak). This is almost certainly correlated with a 98% decline in owl productivity as well as that of the local [[Stoat|stoats]] (the [[long-tailed jaeger]] and [[Arctic fox]]es, though previously thought to be almost as reliant on lemmings, seem to be more loosely coupled and more generalized and did not decline as much).<ref name= Schmidt>{{cite journal|pmid=22977153}}</ref><ref>{{cite journal|doi=10.4080/gpcw.2011.0113}}</ref> The amount of lemming mounds is much less than it once in northern Greenland and any variety of [[population cycle]] has been apparently abandoned by what remains of the lemmings.<ref name= Schmidt/>' ]
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[ 0 => 'Snowy owls may be active to some extent at both day, from dawn to dusk, and night.<ref name= Konig/><ref name="Manniche" /> Snowy owls have been seen to be active even during the very brief winter daytime in the northern winter.<ref name= Voous/> During the Arctic summer, snowy owls may tend to peak in activity during the twilight that is the darkest time available given the lack of full nightfall.<ref name= Voous/><ref>Young, C.M. (1973). ''The Snowy Owl migration of 1971–72 in the Sudbury region of Ontario''. American Birds 27(1): 11–12.</ref><ref>Shields, M. (1969). ''Activity cycles of Snowy Owls at Barrow, Alaska''. Murrelet 50 (2): 14–16.</ref> Reportedly, the peak time of activity during summer is between 9:00&nbsp;pm and 3:00&nbsp;am in Norway.<ref name= Hagen>Hagen, Y. (1960). ''The Snowy Owl on Hardangervidda in the Summer of 1959''. Papers of The Norwegian State Game Research. 2, No. 7.</ref> The peak time of activity for those owls that once nested on Fetlar was reported between 10:00 and 11:00&nbsp;pm.<ref name= Tulloch>Tulloch, R. J. (1968). ''Snowy Owls breeding in Shetland in 1967''. British Birds 61:119–132.</ref> According to one authority, the least active times are at noon and midnight.<ref name= Watson/> As days become longer near autumn in [[Utqiaġvik, Alaska|Utqiaġvik]], the snowy owls in the tundra become more active around nightfall and can often be seen resting during the day, especially if it is raining.<ref>Shields, M. (1969). ''Activity cycles of Snowy Owls at Barrow, Alaska''. Murrelet 50 (2):14–16.</ref> During winter in [[Alberta]], snowy owls were tracked in the daytime, despite being also active at night (as they were deemed too difficult to track). In the study, they were most active from 8:00–10:00&nbsp;am and 4:00–6:00&nbsp;pm and often rested mostly from 10:00&nbsp;am to 4:00&nbsp;pm. The owls were perched for 98% of observed daylight and seemed to time their activity to peak times for rodents.<ref>Boxall, P. C. & Lein, M. R. (1989). ''Time budgets and activity of wintering Snowy Owls''. Journal of Field Ornithology 60 (1): 20–29.</ref> The variation of activity is probably in correspondence with their primary prey, the [[lemming]]s, and like them, the snowy owl may be considered [[Cathemerality|cathermal]].<ref name= Konig/><ref name= Voous/><ref name="National Geographic">{{cite web|title=Snowy Owl (Nyctea Scandia)|url=http://animals.nationalgeographic.com/animals/birds/snowy-owl/|website=animals.nationalgeographic.com|publisher=National Geographic|date=11 November 2010}}</ref> This species can withstand extremely cold temperatures, having been recorded in temperatures as low as minus 62.5 [[Celsius|degrees Celsius]] with no obvious discomfort and also withstood a 5-hour exposure to minus 93 degrees Celsius but may have struggled with oxygen consumption by the end of this period. The snowy owl has perhaps the second lowest [[thermal conduction]] to the plumage on average of any bird after only the [[Adelie penguin]] (''Pygoscelis adeliae'') and rivals the best insulated mammals, such as [[Dall sheep]] (''Ovis dalli'') and [[Arctic fox]], as the best insulated polar creature.<ref name= Voous/><ref name= Gessaman>Gessaman, J. A. (1972). ''Bioenergetics of the snowy owl (Nyctea scandiaca)''. Arctic and Alpine Research, 4(3), 223–238.</ref><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/condor/v057n06/p0362-p0365.pdf|author=Irving, L. |title=Nocturnal decline in the temperature of birds in cold weather|doi=10.2307/1364794}}</ref> Presumably as many as 7 rodents would need to be eaten daily to survive an extremely cold winter's day.<ref name= Voous/> Adults and young both have been seen to shelter behind rocks to shield themselves from particularly harsh winds or storms.<ref name= Holt/> Snowy owls often spending a majority of time on the ground, perched mostly on a slight rise of elevation.<ref name= Konig/> It has been interpreted from the morphology of their skeletal structure (i.e. their short, broad legs) that snowy owls are not well-suited to perching extensively in trees or rocks and prefer a flat surface to sit upon.<ref name= Potapov/> However, they may perch more so in winter though do so only mainly when hunting, at times on [[hummock]]s, [[Fence]]posts, [[telegraph pole]]s by roads, [[Radio tower|radio]] and [[transmission tower]]s, [[Hay]]stacks, [[chimney]]s and the roofs of houses and large buildings.<ref name= Voous/> Rocks may be used as perches at times in all seasons.<ref name= Voous/> Though often relatively sluggish owls, like most related species, they are capable of sudden dashing movements in various contexts.<ref name= Potapov/> Snowy owls can walk and run quite quickly, using outstretched wings for balance if necessary.<ref name= Konig/> This owl flies with fairly rowing wingbeats, occasionally interrupted by gliding on stretched wings. The flight is fairly buoyant for a ''Bubo'' owl.<ref name= Konig/><ref name= Holt/> When displaying, the male may engage in an undulating flight with interspersed wingbeats and gliding in a slight dihedral, finally dropping rather vertically to the ground.<ref name= Konig/> They are capable for swimming but do not usually do so. Some seen to be swimming were previously injured but young have been seen to swim into water to escape predators if they cannot fly yet. They will also drink when unfrozen water is available.<ref name= Holt/><ref name= Tulloch/><ref>Mebs, T. & Scherzinger, W. (2000). ''Snowy Owl''. In: ''Die eulen Europa: biolgie, kennzeichen, bestande'', edited by T. Mebs and W. Scherzinger, 167–183. Stuttgart: Franckh-Kosmos Verlags-Gmbh and Co.</ref> Snowy owl mothers have been observed to [[Preening (bird)|preen]] their young in the wild, while pairs in captivity have been observed to allopreen.<ref name= Watson/> In the period leading up to breeding, snowy owls switched regularly between searching (for nesting grounds) and loafing, often searching less when snow cover was less extensive.<ref>Therrien, J. F., Pinaud, D., Gauthier, G., Lecomte, N., Bildstein, K. L., & Bety, J. (2015). ''Pre-breeding prospecting behaviour of snowy owls'' (data from Therrien et al. 2015)-reference-data.</ref> ', 1 => 'It is fair to say that the snowy owl is a partial, if fairly irregular, [[Bird migration|migrant]], having a very broad but patchy wintering range.<ref name= Konig/> 1st year birds tend to disperse farther south in winter than older owls with males wintering usually somewhat more to the south than females of equivalent ages, adult females often wintering the farthest north.<ref name= Voous/><ref name= Scandinavica>Kerlinger, P. & Lein, M.R. (1986). ''Differences in winter range among age-sex classes of Snowy Owls Nyctea scandiaca in North America''. Ornis Scandinavica. 17(1): 1–17.</ref> The snowy owl likely covers more ground than almost any other owl in movements but many complex individual variations are known in movements, and they often do not take the traditional north–south direction that might be assumed.<ref name= Holt/> Migratory movements appear to be somewhat more common in America than in Asia.<ref name= Konig/> A study of wintering owls in the [[Kola Peninsula]] determined that the mean date of arrival of owls was 10 November with a departure date of 13 April, covering an average of {{convert|991|km|mi|abbr=on}} during the course of the wintering period and clustering where [[Ptarmigan|prey]] was more concentrated.<ref>Øien, I. J., Aarvak, T., Jacobsen, K. O., & Solheim, R. (2018). ''Satellite Telemetry Uncovers Important Wintering Areas for Snowy Owls On the Kola Peninsula, Northwestern Russia''. Орнитология, 42, 42–49.</ref> Some variety of movements recorded each autumn and snowy owls winter annually in plains of [[Siberia]] and Mongolia and [[prairie]]s and [[marsh]]lands of Canada.<ref name= Voous/> The [[Great Plains]] area of southern Canada host wintering snowy owls about 2 to 10 times more frequently than other areas of the continent.<ref name= Holt/> Some weak correlation has made with individuals having some level of fealty to certain wintering sites.<ref>Oeming, A. F. (1957). ''Notes on the Barred Owl and the Snowy Owl in Alberta''. Blue Jay 15:153–156.</ref><ref>Follen, D. & Luepke, K. (1980). ''Snowy Owl recaptures''. Inland Bird Banding 52: 60.</ref> Wintering snowy owls, a total of 419, recorded in [[Duluth, Minnesota]] from 1974 to 2012 would occur in larger numbers in years where [[Brown rat|rats]] were more plentiful. The amount of individual returns among 43 Duluth-wintering owls was fairly low in subsequent winters (8 for 1 year, a small handful in the next few years, and 9 in non-consecutive years).<ref name= Holt/> Sometimes surveys appeared to reveal hundreds of wintering snowy owls on coastal sea ice during an irruptive year.<ref name= Voous/><ref name= Marine/> Three siblings that hatched in same nest in [[Cambridge Bay]] were recovered in drastically different spots at least a year later: one in eastern [[Ontario]], one in [[Hudson Bay]] and one in [[Sakhalin Island]].<ref name= Parmelee/> A nestling banded in [[Sogn og Fjordane|Hordaland]] was recovered {{convert|1380|km|mi|abbr=on}} to the northeast in [[Finnmark]].<ref name= Voous/> In the [[Logan Airport]], 17 of 452 owls were recorded to return, eleven the following year, three 2 years later, and then singles variously 6, 10 and 16 years later.<ref name= Holt/> A banded female from Utqiaġvik was recorded to migrate over {{convert|1928|km|mi|abbr=on}} along seacoast down to Russia, returning over {{convert|1528|km|mi|abbr=on}} and covering at least {{convert|3476|km|mi|abbr=on}} in total. Another banded young female from Utqiaġvik went to the same Russian areas, returned to Utqiaġvik and then onto [[Victoria Island (Canada)|Victoria Island]], but did appear to breed, while another also covered a similar route but ended up nesting on [[Banks Island]]. Another female migrated to the [[Canada–United States border]], then moved back to the [[Gulf of Alaska]], then to winter in the same border areas and then finally to both Banks and Victoria Island.<ref name= Holt/><ref name= Fuller/> Snowy owls from the Canadian Arctic were monitored to have covered an average of {{convert|1100|km|mi|abbr=on}} in one autumn then covered an average of {{convert|2900|km|mi|abbr=on}} a year later.<ref name= Therrien2>Therrien, J.-F., Fitzgerald, G., Gauthier G. & Bêty, J. (2011). ''Diet-tissue discrimination factors of carbon and nitrogen stable isotopes in blood of Snowy Owl (Bubo scandiacus)''. Canadian Journal of Zoology 89 (4): 343–347.</ref> In late winter, owls from the same area were found to have covered a mean of {{convert|4093|km|mi|abbr=on}} of ground in the tundra and spent a mean of 108 days, apparently searching for a suitable nesting situation the entire time.<ref>Therrien, J.-F. , Gauthier, G., Pinaud, D. & Bêty, J. (2014). ''Irruptive movements and breeding dispersal of Snowy Owls: a specialized predator exploiting a pulsed resource''. Journal of Avian Biology. 45(6): 536–544.</ref>', 2 => 'In no fewer than 24 winters between 1882 and 1988, large numbers have occurred in Canada and the United States. These were [[Irruptive growth|irruption]] years.<ref name= Voous/> Record breeding irruptive years were recorded in the winters of 2011–2012 and 2014–2015.<ref name= Holt/><ref>Jorgensen, J. G., Dinan, L. R., & Walker Jr, T. J. (2012). ''Snowy Owl Invasion of 2011–12''.</ref> In the 1940s, it was calculated that the mean gape in time between large irruptions was 3.9 years.<ref name= Gross1/> Southbound movements as such are much more conspicuous after peak vole years, once thought to be separated by periods of around 3–7 years.<ref name= Voous/><ref>Snyder, L. L. (1943). ''The Snowy Owl migration of 1941–42''. Wilson Bulletin 55 (1):8–10.</ref><ref>Shelford, V. E. (1945). ''The relation of Snowy Owl migration to the abundance of the Collared Lemming''. Auk 62 (4):592–596.</ref><ref>Chitty, H. (1950). ''Canadian Arctic wild life enquiry, 1943–1949: With a summary of results since 1933''. Journal of Animal Ecology 19 (2):180–193.</ref><ref name="Godfrey" /> However, more extensive research has weakened the argument that irruptions are entirely food-based and the data indicates that irruptive movements are far from predictable. This is because a statewide survey in Alaska found no statewide synchrony in lemming numbers. Therefore, rather than decline of lemmings, it is the successful productivity of several pairs that plays the role, resulting in a large number of young owls that then irrupt. However, the snowy owls cannot breed in high numbers unless lemmings are widely available on the tundra.<ref name= Holt/><ref name= Kerlinger2/><ref name= Gross/><ref>Pitelka, F. A. & Batzli, G. O. (1993). ''Distribution, abundance, and habitat use by lemmings on the north slope of Alaska''. In: ''The biology of lemmings'', edited by N. C. Stenseth and R. A. Ims, 213–236. London: Academic Press.</ref><ref name="Krebs">Krebs, C. J. (1993). ''Are lemmings large Microtus or small reindeer? A review of lemming cycles after 25 years and future recommendations for future work''. In: ''The biology of lemmings'', edited by N. C. Stenseth and R. Ims, 247–260. London: Academic Press for the Linnean Society of London.</ref> This connection of irruptions to high years of productivity was confirmed in a study by Robillard et al. (2016).<ref>Robillard, A., Therrien, J. F., Gauthier, G., Clark, K. M., & Bêty, J. (2016). ''Pulsed resources at tundra breeding sites affect winter irruptions at temperate latitudes of a top predator, the snowy owl''. Oecologia, 181(2), 423–433.</ref> About 90% of the snowy owls seen in irruptive years from 1991 to 2016 that were ageable were identified as juveniles.<ref name= Santonja/>', 3 => 'Snowy owls may hunt at nearly at any time of the day or night, but may not attempt to do so during particularly severe weather.<ref name= Holt/> During the [[summer solstice]], the owls appear to hunt during "theoretical nightfall".<ref name= Holt/> [[Night-vision device]]s have allowed biologists to observe that snowy owls hunt quite often during the extended nighttime during the northern winter.<ref name= Potapov/><ref name= Holt/><ref name="Manniche" /> Prey are both taken and eaten on the ground.<ref name= Konig/> Snowy owls, like other carnivorous birds, often swallow their small prey whole.<ref name= Konig/> Strong stomach juices digest the flesh, while the indigestible bones, teeth, fur, and feathers are compacted into oval pellets that the bird regurgitates 18 to 24 hours after feeding. Regurgitation often takes place at regular perches, where dozens of pellets may be found. Biologists frequently examine these pellets to determine the quantity and types of prey the birds have eaten. When large prey are eaten in small pieces, pellets will not be produced.<ref>[http://www.owlpages.com/owls.php?genus=Bubo&species=scandiacus Snowy Owl — ''Bubo scandiacus'', formerly ''Nyctea scandiaca'']. owlpages.com</ref> Larger prey is often torn apart, sometimes include removal of the head, with the large muscles, such as the [[humerus]] or [[Thorax|breast]], typically eaten first.<ref name= Holt/> The scattering of remains that results from the increment feeding on larger prey is thought to result in under-identification of them compared to smaller prey items.<ref>{{cite journal|title=A taphonomic investigation of small vertebrate accumulations produced by the snowy owl (''Bubo scandiacus'') and its implications for fossil studies|doi=10.1016/j.palaeo.2018.10.018}}</ref> The aptitude for hunting by day, hunting from the ground and hunting in almost always completely open and treeless areas are the primary ways in which the snowy owl differs in hunting from other ''Bubo'' owls. Otherwise, the hunting habits are similar.<ref name= Holt/><ref name= Johnsgard>[[Paul Johnsgard|Johnsgard, P. A.]] (1988). [https://digitalcommons.unl.edu/johnsgard/46/ ''North American owls: biology and natural history'']. Smithsonian Institution.</ref> It is thought, due to their less refined hearing compared to other owls, prey is usually perceived via vision and movement.<ref name= Voous/><ref name= Holt/> Experiments indicate that snowy owls can detect prey from as far as {{convert|1.6|km|mi|abbr=on}} away.<ref name= Smith/> Snowy owls generally use a rise or, occasionally, a perch while hunting.<ref name= Konig/> 88% of observed 34 hunts in Utqiaġvik were undertaken from an elevated watch-site (56% mounds or rises, 37% [[telephone pole]]s).<ref name= Holt/> Their hunting style may recall that of [[Buteo|buzzard]]s, with the hunting owl sitting rather low and perching immobile for a long spell.<ref name= Hume/> Although their usual flight is a slow, deliberate downbeat on the broad, fingered wings, when prey is detected from their perch, flight may undertaken with a sudden, surprisingly quick accelerated style with interspersed wing beats.<ref name= Hume/><ref>{{cite journal|author=Hohn, E. O. |year=1973|title=Winter hunting of Snowy Owls in farmland|journal= Canadian Field-Naturalist|volume= 87 |issue=4|pages= 468–469}}</ref> In Utqiaġvik, snowy owls may most frequently engage in a brief pursuit hunting style.<ref name= Holt/> In high winds capable of keeping their bulk aloft, snowy owls may too engage in a brief [[Levitation|hovering]] flight before dropping onto prey.<ref name= Watson/> When hunting fish, apparently, some snowy owls will hover in a style reminiscent of the [[osprey]] (''Pandion haliaetus''), although in at least one other case a snowy owl was observed to capture fish by lying on its belly upon a rock by a fishing hole.<ref name= Audubon>Audubon, J. J. (1840). ''The Birds of America''. Dover Publications, Inc., New York, NY, USA.</ref> A dashing stoop or pounce down onto their prey, ending in a high-impact "wallop", is fairly commonly recorded.<ref name= Holt/><ref name= Hume/> Another common technique is the "sweep", wherein they fly by and grasp the prey while continuing to fly.<ref name= Holt/><ref>{{cite journal|author=Dancey, H.E. |year=1983|title=Winter foraging habits of a Snowy Owl|journal= Indiana Audubon Quarterly|volume= 61|issue=4|pages= 136–144}}</ref> In winter, snowy owls have been shown to be able to "snow plunge" to capture prey in the [[Subnivean climate|subnivean zone]], under at least {{convert|20|cm|in|abbr=on}} of snow.<ref name= Smith/> Perhaps least frequently, snowy owls may pursue their on foot, in doing so never taking wing.<ref name= Holt/> Snowy owls have been known to capture [[Bird migration|night-migrating]] [[passerine]]s and [[shorebird]]s, sometimes perhaps on the wing, as well as large and/or [[Bird of prey|potentially dangerous]] birds that were caught in air by snowy owls during daylight.<ref name= Holt/> On the wing pursuits against other various other carnivorous birds are sometimes undertaken as well to [[Kleptoparasitism|kleptoparasitize]] the prey caught by the other birds.<ref name= Holt/><ref>Duffy, D. C., Beehler B. & Haas, W. (1976). ''Snowy Owl steals prey from Marsh Hawk''. Auk 93 (4): 839–840.</ref> Few variations of hunting technique were observed in winter observations from [[Alberta]], almost all of the hunts being with the sit-and-wait method (also known as still-hunts). Adult females in Alberta had a considerably better hunting rate than juvenile females.<ref name= Boxall2>{{cite journal|doi=10.14430/arctic2326|title=Feeding ecology of Snowy Owls (''Nyctea scandiaca'') wintering in S. Alberta}}</ref> Much as in Alberta, in [[Syracuse, New York]], 90% of 51 hunts were still-hunting, with the sweep variant used after perch departure in 31% of hunts and the pounce method in 45% of hunts. The Syracuse-wintering owls used tall perches, a mixture of manmade objects and trees of around {{convert|6|m|ft|abbr=on}} high, in nearly 61% of hunts, while nearly 14% were from low perches (i.e. fence-posts, snow banks and scrap piles) about half as high as the tall perches and started from a ground position nearly 10% of the time.<ref name= Winter>Winter, R. E. (2016). ''Hunting Behaviors and Foraging Success of Winter Irruptive Snowy Owls in New York''. SUNY College of Environmental Science and Forestry, Thesis.</ref> In Sweden, males hunted from a perch more so than did females and adults both focused on significantly smaller prey (small [[mammal]]s) and may have had more success hunting than juvenile snowy owls.<ref name= Lind/> Some snowy owls can survive a fast for up to about 40 days off of [[Fatty acid metabolism|fat reserves]].<ref name= Hume/> These owls were found to have extremely thick [[Subcutaneous tissue|subcutaneous fat deposits]] of around {{convert|19|to|22|mm|in|abbr=on}} and it is likely owls that overwinter in the Arctic rely heavily on these to survive during this scarce time, in combination with lethargic, energy-conserving behavior.', 4 => 'Data from the [[Logan Airport]] in over 6,000 pellets shows that meadow vole and brown rat predominated the diet in the area, supplanted by assorted birds both small and large.<ref name= Holt/><ref name= Smith/> [[American black duck]]s were primarily taken among bird species with other birds taken here including relatively large and diverse species [[Canada geese]] (''Branta canadensis''), brants, [[American herring gull]]s (''Larus argentatus''), [[double-crested cormorant]] (''Phalacrocorax auritus''), [[great blue heron]] (''Ardea herodias''), in addition to some formidable mammals such as [[Cat|house cat]], [[American mink]] (''Mustela vision''), and [[striped skunk]] (''Mephitis mephitis'').<ref name= Holt/><ref name= Smith/> Given the large size of some of this prey, it can be projected that the snowy owl can kill adult prey of around twice their own weight (i.e. geese, cats, skunks, etc.).<ref name= Holt/><ref name= Smith/> Other large prey is sometimes taken by snowy owls, all roughly within the {{convert|2|to|5|kg|lb|abbr=on}} weight range often include adults of large [[leporid]]s such as [[Arctic hare]] (''Lepus arcticus''),<ref name= Holt/> [[Alaskan hare]] (''Lepus othus''),<ref>Best, T. L., & Henry, T. H. (1994). ''Lepus othus''. Mammalian Species, (458), 1–5.</ref> [[mountain hare]]<ref>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V54/V54_N08/V54_N08_P307_320_A051.pdf|author=Bergman, G. |year=1961|title=The food of birds of prey and owls in Fenno-Scandia|journal= British Birds|volume= 54|issue=8|pages= 307–320}}</ref> and [[white-tailed jackrabbit]]s (''Lepus townsendii'').<ref name= Boxall2/> As well as several species of geese, probable cygnets of [[Tundra swan|Bewick's swan]]s (''Cygnus columbianus bewickii'')<ref>Nagy, S., Petkov, N., Rees, E., Solokha, A., Hilton, G., Beekman, J., & Nolet, B. (2012). [https://www.unep-aewa.org/en/publication/international-single-species-action-plan-conservation-northwest-european-population International single species action plan for the conservation of the northwest European population of Bewick's Swan (''Cygnus columbianus bewickii'')]. Wetlands International and The Wildfowl & Wetlands Trust (WWT), AEWA Technical Series, (44).</ref> as well as adults of the following: [[western capercaillie]] (''Tetrao urogallus'') (of both sexes),<ref>Gilyazov, A. V. (2005). ''Snowy Owl Nyctea scandiaca Linnaeus, 1758''. Red-data Book of the Murmansk Region. Murmansk: Murmansk book publishers: 316—318. [in Russian].</ref> [[greater sage-grouse]] (''Centrocercus urophasianus'')<ref>{{cite journal|doi=10.1002/jwmg.21168}}</ref> and [[yellow-billed loon]]s (''Gavia adamsii'').<ref>Uher-Koch, B. D., M. R. North, and J. A. Schmutz (2020). Yellow-billed Loon (''Gavia adamsii''), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.</ref> At the other end of the scale, the snowy owl has been known to take birds down to size of {{convert|19.5|g|oz|abbr=on}} [[dark-eyed junco]]s (''Junco hyemalis'') and mammals down the size of {{convert|8.1|g|oz|abbr=on}} [[common shrew]]s (''Sorex araneus'').<ref name= Hakala/><ref name= Young/><ref name= CRC1>Dunning, Jr., J. B. (1993). ''CRC handbook of avian body masses''. CRC Press, Boca Raton, FL.</ref> Fish are rarely taken anywhere but the snowy owl has been known to prey upon [[Arctic char]] (''Salvelinus alpinus'') and [[lake trout]] (''Salvelinus namaycush'').<ref name= Voous/><ref name= Gross/><ref name= Bailey>Bailey, A. M. (1948). ''Birds of Arctic Alaska''. Colorado Mus. Nat. Hist., Popular Ser., 8.</ref>', 5 => 'When it goes south to winter outside of the Arctic, the snowy owl has a potential to interact with a number of additional predators.<ref name= Voous/> By necessity, it shares its wintertime diverse prey with a number of formidable predators.<ref name= Voous/><ref name= Holt/> These are known to include their cousins, the [[great horned owl]] and the [[Eurasian eagle-owl]]. They are relieved of heavy competition from the related species by differing temporal activity, i.e. being more likely to actively hunt in daytime, and by habitat, using rather more open (quite often nearly treeless) habitats than them.<ref name= Potapov/><ref name= Voous/> During a study of wintering snowy owls in [[Saskatchewan]], the authors indicated that the snowy owls may avoid areas inhabited and defended by great horned owls. Although they usually occurred here outside of a {{convert|800|m|ft|abbr=on}} radius of central great horned owl ranges, they did not avoid the {{convert|1600|m|ft|abbr=on}} radius and different habitat usage may be a dictating factor.<ref name= Chang2>Chang, A. M. (2017). ''Habitat use, movement patterns, and body condition of male and female Snowy Owls (Bubo scandiacus) in winter'' (Doctoral dissertation, University of Saskatchewan).</ref> Given their mildly slighter size, it is unlikely that great horned owls (unlike the larger eagle-owl) would regularly dominate snowy owls in interactions and either species may give way to other depending on the size and disposition of the owls involved.<ref name= Potapov/><ref name= Voous/> Little study has been undertaken into the [[Trophic level|trophic competition]] of snowy owls with other predators during winter and, due to their scarcity, few predators are likely to expel much energy on competitive interactions with them, although many other predators will engage in anti-predator [[Mobbing (animal behavior)|mobbing]] of snowy owls.<ref name= Voous/><ref name= Holt/> Largely in winter, snowy owls have been the victim of a number of larger avian predators, though attacks are likely to be singular and rare.<ref name= Voous/><ref name= Holt/> Instances of predation on snowy owls are known to have been committed several times in winter only by [[Eurasian eagle-owl]]s.<ref name= Mikkola3>{{cite journal|url=https://britishbirds.co.uk/wp-content/uploads/article_files/V69/V69_N04/V69_N04_P144_154_A030.pdf|author=Mikkola, H. |year=1976|title=Owls killing and killed by other owls and raptors in Europe|journal= British Birds|volume= 69|pages= 144–154}}</ref> Additionally, [[golden eagle]]s (''Aquila chrysaetos'') have been known to prey on snowy owls as well as all northern [[sea eagle]]s: the [[Bald eagle|bald]] (''Haliaeetus leucocephalus''), [[White-tailed eagle|white-tailed]] (''Haliaeetus albicilla'') and [[Steller's sea eagle]]s (''Haliaeetus pelagicus'').<ref name= Holt/><ref name= Campbell/><ref>{{cite journal|author=Johnson, M.J. |year=1995|title=Bald Eagle predation on Snowy Owl|journal= Loon|volume= 67|issue=2|pages=107}}</ref> Snowy owls are also sometimes killed by birds that are mobbing them. In one instance, a [[peregrine falcon]] killed a snowy owl in a stoop after the owl had itself killed a fledgling falcon.<ref name= Bent/><ref name= Bailey/><ref>Nelson, E. W. (1887). ''Birds of Alaska'', p. 35-222. In H. W. Henshaw [ed.], Report upon natural history collections made in Alaska between the years 1877 and 188 1. No. III Arctic Series, Signal Service, U.S. Army, Government Printing Office,-Washington, DC.</ref> Anecdotal report indicate predation by [[gyrfalcon]]s (on snowy owls of unknown age and condition) but it was possibly also an act of mobbing.<ref name= Heggoy>Heggøy, O., & Øien, I. J. (2014). ''Conservation status of birds of prey and owls in Norway''. NOF/BirdLife Norway-Report, 1, 1–129.</ref> In another, a huge [[Flock (birds)|throng]] of [[Arctic tern]]s (''Sterna paradisaea'') relentlessly swarmed and attacked a snowy owl until it meet its demise.<ref>Meinertzhagen, R. (1959). ''Pirates and Predators: The piratical and predatory habits of birds''. Oliver & Boyd.</ref>', 6 => 'Almost certainly more often than being victim of other predators, snowy owls are known to dominate, kill and feed on a large diversity of other predators.<ref name= Voous/><ref name= Mikkola3/> Snowy owls, much like other ''Bubo'' owls, will opportunistically kill other birds of prey and predators. Although they will readily plunder the nests of other raptorial birds given the opportunity, most predations are on full-grown raptorial birds during winter due to the scarcity of raptor nests in the open tundra.<ref name= Voous/> In addition, most competing predators of the Arctic, excepting the very large mammals, are probably vulnerable to a hungry snowy owl.<ref name= Voous/><ref name= Holt/> In data from the [[Logan Airport]] alone over different winters, the snowy owls were observed to have preyed upon an impressive diversity of other raptorial birds: [[rough-legged buzzard]]s, [[American kestrel]]s (''Falco sparverius''), [[peregrine falcon]]s, [[barn owl]]s, other snowy owls, [[barred owl]]s (''Strix varia''), [[northern saw-whet owl]]s (''Aegolius acadicus'') and [[short-eared owl]]s. While owls are likely encountered during corresponding hunting times, it is likely that the swift falcons are usually ambushed at night (much as other ''Bubo'' owls will do).<ref name= Holt/><ref name= Smith/> In both the tundra and the wintering ground, there are several accounts of predation by snowy owls on short-eared owls.<ref name= Potapov/><ref name= Mikkola3/><ref>{{cite journal|doi=10.2307/1368028}}</ref> In addition, snowy owls have been known to prey on [[northern harrier]]s,<ref name= Holt/><ref name= Smith/> [[northern goshawk]]s (''Accipiter gentilis'')<ref name= Voous/> and [[gyrfalcon]]s.<ref name= Voous/><ref name= Mikkola3/> In a few cases, both juvenile and adult [[Arctic fox]]es have been known to fall prey to snowy owls.<ref name= Parker/><ref name= Stenkewitz/><ref name= Krechmar/><ref name="Gilg">{{cite journal|doi=10.1111/j.2006.0030-1299.14125.x}}</ref><ref>{{cite journal|title=''Alopex lagopus''|doi=10.1644/0.713.1}}</ref> A wintering snowy owl in [[Saskatchewan]] was observed to have preyed on an adult [[red fox]] (''Vulpes vulpes''). Predation by snowy owls on red foxes was also reported in the [[Irkutsky District]] of Russia. With an adult weight around {{convert|6|kg|lb|abbr=on}} (and far from defenseless), red fox may be the largest known prey known for snowy owls.<ref name= Maleev/><ref>{{cite journal|doi=10.29173/bluejay3979}}</ref> Besides aforementioned predation on domestic cats and skunks, several members of the [[weasel]] family, both small and relatively large, are known to be opportunistically hunted by snowy owls.<ref name= Potapov/><ref name= Voous/><ref name= Holt/><ref name= Smith/><ref name= Hakala/><ref>{{cite journal|doi=10.2307/3565424}}</ref> As a result of its potential predator status, the snowy owl is frequently mobbed at all times of the year by other predatory birds, including fierce dive-bombing by several of the northern falcons on the wintering grounds, including even by the relatively tiny but fierce and very agile [[Merlin (bird)|merlin]] (''Falco columbarius''). The much bulkier snowy owls cannot match the speed and flight ability of a falcon, ai may be almost relentlessly tormented by some birds such as peregrines.<ref name= Voous/><ref name= Mikkola3/><ref>{{cite journal|doi=10.29173/bluejay208}}</ref>', 7 => 'In Utqiaġvik, of 239 recorded breeding attempts, 232 were monogamous, the other 7 [[Bigamy|social bigamy]].<ref name= Holt/> On [[Baffin Island]], 1 male bred with 2 females and sired 11 total fledged young.<ref name= Watson/> Another case of bigamy was reported in Norway where the 2 females bred to one male were {{convert|1.3|km|mi|abbr=on}} apart in nest site location.<ref name= Hagen/> On Feltar from 1967 to 1975, a male breed with two females, 1 younger and was possibly his own [[Incest|daughter]]. In the Feltar males first time breeding with both females, he did not bring food to the younger female. However, when older female disappeared the following year, the male and younger female producing 4 young, but disappeared the subsequent year altogether in 1975.<ref name= Robinson/> There are also unconfirmed cases of [[polyandry]], with 1 female being fed by 2 males. Snowy owls can breed once per year but when food is scarce many do not even attempt to breed.<ref name= Konig/><ref name= Voous/> Despite frequent wandering in search of food, they generally adhere more so than to a strict breeding season than [[short-eared owl]]s nesting in the tundra.<ref name= Voous/> 9 radio-tagged female snowy owls about [[Bylot Island]] were tracked to study how pre-laying snow cover effects their searching behavior for breeding area. These tracked females searched an average of 36 days and covered an average of {{convert|1251|km|mi|abbr=on}}. It is thought that the male and female mutually find an attractive breeding spot independently and converge.<ref>{{cite journal|doi=10.1186/s40462-015-0028-7}}</ref> The breeding territory normally averages about {{convert|2.6|km2|sqmi|abbr=on}} as in both [[Baffin Island]] and [[Ellesmere Island]] but varies in accordance to abundance of food and density of owls.<ref name= Konig/><ref name= Watson/><ref name= MacDonald/> Nesting territories average at Baffin island in the range of {{convert|8|to|10|km2|sqmi|abbr=on}} during poor lemming years.<ref name= Watson/> Nesting territories may up to {{convert|22|km2|sqmi|abbr=on}} on [[Southampton Island]] and had a mean distance of {{convert|4.5|km|mi|abbr=on}} between active nests.<ref name= Sutton1/> In Utqiaġvik, nesting pairs can vary from none to at least 7 and the territories average {{convert|5|to|10|km2|sqmi|abbr=on}}, with mean nest distances of {{convert|1.5|to|6|km|mi|abbr=on}}.<ref name= Pitelka/> In the Norwegian highlands, nesting occurs only at times of plenty distances of {{convert|1.2|to|3.7|km|mi|abbr=on}} between nests, averaging {{convert|2.1|km|mi|abbr=on}}.<ref name= Hagen/> Males marks territory with singing and display flights and likely always initiates.<ref name= Watson/> During the display, he engages in exaggerated wing beats with a shallow undulating and bouncy courtship flight with wings held in a [[Dihedral (aeronautics)|dihedral]]. He often drops to the ground but then flies again to only glide gently back down. Overall, the flight is somewhat reminiscent of the flight of a [[moth]].<ref name= Watson/><ref name= Pitelka/><ref name= Tulloch/><ref name= Robinson/> Females will answer her mate with her song during courtship.<ref name= Konig/> While courting, the male often also carries a lemming in his bill, then bows with cocked tail, similarly as in related owls (seldom displaying some other prey like [[snow bunting]]s). He then flaps his wings open in an emphatic manner, with the ground display being relatively brief (about 5 minutes). The female may possibly refuse to breed if ritual not performed.<ref name= Watson/><ref name= Taylor/> A possible courtship was engaged in by a male in southern Saskatchewan when a female was sighted.<ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v094n01/p0079-p0081.pdf|author1=Boxall, P. C. |author2= Lein, M. R. |year=1982|title=Possible courtship behavior of Snowy Owls in winter|journal= Wilson Bulletin|volume= 94|pages=79–81}}</ref> On Southampton Island, at least 20 males observed in late May in a "lemming year".<ref name= Voous/><ref name= Sutton1/> Nesting territory defense displays, not highly different from courtship displays, includes undulating flight and stiffly raised wings with bouts of exaggerated, delayed wing beats, looking like enormous white moths exposing their white wings under the sun.<ref name= Taylor/> At times, competing males will interlock claws in mid-air.<ref name= Voous/> Territorial and nuptial displays are followed by a ground display by the male with the wings arched up in an "angel" posture, visible for well over a mile.<ref name= Voous/>', 8 => 'Most individuals arrive at the nest site by April or May with a few overwintering arctic exceptions.<ref name= Murie/><ref name= Marine/><ref name= Pitelka2/><ref name= Fuller/> Males advertises potential nest sites to his mate by scratching the ground and spreading his wings over it.<ref name= Konig/> The nest is usually a shallow depression on a windswept eminence in the open tundra. There seems to be a variety of qualifiers for appropriate nest sites. The nest site is typically snow-free and dry relative to the surrounding environment, usually with a good view of the surrounding landscape. The nest may be made of [[ridge]]s, [[Mound|elevated mound]]s, high [[polygon]]s, [[hummock]]s, hills, man-made mounds and occasionally [[Outcrop|rocky outcrops]]. If covered with vegetation, taller plants that may obstruct view are plucked away sometimes.<ref name= Konig/><ref name= Voous/><ref name= Watson/><ref name= Pitelka2/><ref name= Holt3>{{cite journal|doi=10.5253/078.097.0422}}</ref> The nest sites are often long-established and naturally created by the freeze-thaw process of the tundra.<ref name= Voous/><ref name= Holt/> [[Bar (river morphology)|Gravel bars]] may be used as well.<ref name= Potapov/> The female may take the most active role in the nest's condition of any owl species.<ref name= Holt/><ref name= Mikkola/> No owl build their own nests but female snowy owls take about three days constructing a scrape, digging with her claws and rotating until a fairly circular bowl is formed. She will still not construct or add foreign materials to the nest (despite some circumstantial evidence of moss and grass from outside the nest mound being found).<ref name= Holt/><ref name= Murie/><ref name= Tulloch/> In two separate cases in Utqiaġvik, two separate females dug out a second scrape to the side and below the main nests and appeared to have called all chicks to the more secluded nest to ride out severe weather until the skies cleared.<ref name= Holt/> The Utqiaġvik nest scrapes averaged {{convert|47.7|x|44|cm|in|abbr=on}} in 91 with a mean depth of {{convert|9.8|cm|in|abbr=on}} while the scrapes were smaller in [[Hooper Bay]], reportedly {{convert|25|to|33|cm|in|abbr=on}} diameter and {{convert|4|to|9|cm|in|abbr=on}} in depth.<ref name= Murie/><ref name= Holt3/> Occasionally, in the lower tundra, snowy owls may too use old nests of [[rough-legged buzzard]]s as well as abandoned [[eagle]] nests.<ref name= Voous/> Unlike other northerly breeding raptorial birds, the snowy owl is not known to nest on cliffs and the like, so do not enter into direct competition with eagles, falcons, ravens or other ''Bubo'' owls when nesting to the relative south.<ref name= Voous/> The area of nest mound often has a relatively rich plant life which attract the lemmings, which may tunnel right under and around the owl's nest.<ref name= Voous/> [[Goose|Geese]], ducks and [[shorebird]]s of several species known to gain incidental protection by nesting close to snowy owls. Conversely, the snowy owls will sometimes kill and eat both young and adults of these birds, which implies a trade-off in the benefits.<ref name= Parmelee/><ref name= Murie/><ref name= Robinson/><ref>{{cite journal|url=https://sora.unm.edu/sites/default/files/journals/wilson/v109n03/p0449-p0461.pdf|author=Tremblay, J. P., Gauthier, G., Lepage, D., & Desrochers, A. |year=1997|title=Factors affecting nesting success in greater snow geese: Effects of habitat and association with snowy owls|journal= The Wilson Bulletin|pages= 449–461|volume=109|issue=3|jstor=4163840}}</ref><ref>{{cite journal|doi=10.1139/z96-210}}</ref><ref>{{cite journal|doi=10.1007/BF02465456|title=How do Brent Geese (''Branta b. bernicla'') cope with evil}}</ref><ref>Smith, P. A. (2003). ''Factors affecting nest site selection and reproductive success of tundra nesting shorebirds'' (Doctoral dissertation, University of British Columbia).</ref>', 9 => 'Food is brought to the nest by males and surplus food is stored nearby.<ref name= Konig/> Females in breeding season often develop a very extensive [[brood patch]] which in this species is a fairly enormous, high vascularized featherless area of pink belly skin.<ref name= Voous/><ref name= Parmelee/> Incubation lasts 31.8–33 days (unconfirmed and possibly dubious reports from as little as 27 to as much as 38-day incubations).<ref name= Konig/><ref name= Murie/><ref name= Robinson/><ref name= Schaanning/> The female alone broods the young, often while simultaneously incubating still unhatched eggs.<ref name= Konig/><ref name= Holt/> Sometimes older chicks incidentally brood their younger siblings and females may shelter the young under her wings during inclement weather.<ref name= Parmelee/><ref name= Watson/> When first feeding the young, the female may dismantle prey to feed the young only the softer body parts then gradually ramping up the size of proportions until they eat a whole prey item.<ref name= Watson/> Aggressive encounters with parent snowy owls are said to be "genuinely dangerous" and one resource claimed the snowy owl to be the bird species with the most formidable nest defense displays towards humans.<ref name= Voous/><ref name= Bent/><ref>Couzens, D. (2008). ''Extreme Birds: The World's Most Extraordinary and Bizarre Birds''. Firefly Books.</ref> The usual response to sighted humans near the nest is mild but continued approach begins to increasingly irritate the parents.<ref name= Holt/> At times, humans are forcefully dive-bombed upon, while other potential threats are dealt with in a “forward-threat” where the male walks towards the intruders, engaging in impressive feather-raising and fanning out of half-spread wings until they run forward and slash with both their feet and bill.<ref name= Voous/><ref name= Bent/><ref name= Watson/><ref name= Sutton1/><ref name= Parmelee/> Fairly serious injuries have been sustained in the worst of snowy owl defensive attacks, including cranial trauma, requiring researchers to make the long trek back to medical care, although human fatalities are not known.<ref name= Sutton/><ref>Barth, E. K. (1950). ''Efter fjallugglor pf Hardangervidda''. Fauna Flora, 45: 235–242.</ref> Snowy owl parents have been seen to aggressively attacked glaucous gulls, arctic fox and dogs in breeding ground in Utqiaġvik.<ref name= Holt/> Non-predatory animals like [[Reindeer|caribou]] in Utqiaġvik and sheep (''Ovis aries'') in Fetlar are attacked as well, possibly to avoid potential trampling of the eggs or the young.<ref name= Parmelee/><ref name= Tulloch/> Males are said to do the majority of nest defense but the female will also often become involved as well.<ref name= Holt/> Analysis showed in [[Lapland, Sweden]], that females in nest defense against people engaged in vocal displays (warning and mewing calls) and that males did not engage in mewing but did engage in most hooting calls, many warning calls and almost all physical attacks.<ref name= Wiklund>Wiklund, C. G., & Stigh, J. (1983). ''Nest defence and evolution of reversed sexual size dimorphism in Snowy Owls Nyctea scandiaca''. Ornis Scandinavica, 58–62.</ref> In other instances, [[distraction display]]s are engaged in against predators, with a "broken-wing act" including high, thin squeals interspersed with weird squeaks, often taking flight only to quickly fall from the sky and imitate a struggle.<ref name= Voous/><ref>[http://animaldiversity.ummz.umich.edu/site/accounts/information/Nyctea_scandiaca.html ADW: ''Nyctea scandiaca: Information'']. Animaldiversity.ummz.umich.edu. Retrieved on 19 October 2010.</ref> One author recorded a male to draw him about {{convert|2|km|mi|abbr=on}} from the nest before ceasing.<ref name= Parmelee/> 77% of 45 distraction displays in Lapland, Sweden were by females.<ref name= Wiklund/>', 10 => 'Hatching intervals are generally from 1 to 3 days, quite often within 37–45 hours apart.<ref name= Watson/><ref name= Tulloch/> New chicks are [[Altriciality|semi-altricial]] (i.e. typically helpless and blind), initially being white and rather wet but dry by the end of the first day. The weight of 7 hatchlings was {{convert|35|to|55|g|oz|abbr=on}}, with an average of {{convert|46|g|oz|abbr=on}} while 3 were {{convert|44.7|g|oz|abbr=on}}.<ref name= Parmelee/><ref name= Watson/> Due to the pronounced asynchrony of the egg-laying and hatching, the size difference between siblings can be enormous and in some cases when the smallest chick weighs only {{convert|20|to|50|g|oz|abbr=on}}, the biggest chick already has attained a weight of around {{convert|350|to|380|g|oz|abbr=on}}.<ref name= Watson/><ref name= Barth/> When the oldest chick is about 3 weeks, the female will start to hunt as well as the male and both may directly feed the young although in some cases they may not need hunt very much if lemmings are particularly numerous.<ref name= Konig/><ref name= Voous/> [[Hoarding (animal behavior)|Caches]] of lemmings around a nest may include more than 80 lemmings that can support the family.<ref name= Voous/> Unlike many owls, the chicks of snowy owls are not known to behave aggressively toward one another or to engage in [[siblicide]], perhaps in part due to the need for energy conservance.<ref name= Holt/><ref name= Tulloch/> Some cases of [[cannibalism]] of chicks by the family group were thought to be cases where chicks die from other causes.<ref name= Sutton/> When they are about 2 weeks, the chicks may begin to walk around the nest site which they leave by 18–28 days, although they are still unable to fly and may find safety in nooks and crannies of vegetation and rocks usually only about {{convert|1|to|2|m|ft|abbr=on}} from the nest mound, as well as via their parents defense.<ref name= Konig/><ref name= Voous/><ref name= Romero>Romero, L. M., Holt, D. W. Maples M. & Wingfield, J. C.. (2006). ''Corticosterone is not correlated with nest departure in Snowy Owl chicks (Nyctea scandiaca)''. General and Comparative Endocrinology 149 (2): 119–123.</ref> Leaving the nest is thought to likely be an anti-predator strategy.<ref name= Holt/><ref>Holt, D. W. & Leasure, S. M. (1993). ''Short-eared Owl (Asio flammeus)''. In: ''The birds of North America, No. 62'', edited by A. Poole and F. Gill. Washington, DC: Acad. Nat. Sci., Philadelphia, PA; Am. Ornithol. Union.</ref> The male snowy owl may drop fresh prey deliveries directly on the ground near the wandering young.<ref name= Voous/> After about three weeks of age, the young may wander fairly widely, rarely to {{convert|1|km|mi|abbr=on}}, but usually stay within {{convert|500|m|ft|abbr=on}} of the nest mound.<ref name= Watson/><ref name= Tulloch/> Threat postures by young in reaction to researchers were first noticeable at about 20–25 days of age and common at about 28 days and the chicks can be impressively quick and agile-footed.<ref name= Holt/><ref name= Watson/> The first fledgling occurs at around 35–50 days, and by 50–60 days the young can fly well and hunt on their own.<ref name= Konig/><ref name= Voous/> The total care period is for 2–3.5 months, increasing in length with increased size of the brood.<ref name= Konig/><ref name= Parmelee/> Although independence was once thought to be sought by late August or early September but is more likely by late September to October when migration season for the species begins.<ref name= Holt/><ref name= Pitelka2/> The nesting cycle is similar in length to the Arctic short-eared owls and faster than Eurasian eagle-owls by up to 2 months.<ref name= Schrezinger>Schrezinger, W. (1974). ''Zur Ethologie und Jugendentwicklung der Schnee-Eule Nyctea scandiaca nach Beobachtungen in Gefangenschaft''. J. Orn, 115: 8–49.</ref>', 11 => 'Sexual maturity reached the following year but the first breeding is normally at no sooner than the end of the second year of life.<ref name= Konig/> There is little strong evidence of typical age of first breeding but initial breeding by males could be inferred by the plumage of males in Utqiaġvik by plumage. At that stage, which the males were essentially all pure white, most were aged to about 3 to 4 years old.<ref name= Holt/> The snowy owl seems to markedly inconsistent in regard to breeding every year, often taking at least up to two years between attempts and sometimes as much as nearly a decade.<ref name= Potapov/><ref name= Fuller/> 7 satellite-marking females in Canada proved that they did breed in consecutive years, with 1 breeding over 3 consecutive years.<ref name= Therrien/> In 23 years at Utqiaġvik, snowys bred in 13 of them.<ref name= Holt/><ref name= Fuller/> Nesting success can reach 90–100% in even the largest clutches in high lemming years.<ref name= Voous/> While over the course of 21 years, 260 total nests were recorded in Utqiaġvik. There, from 4–54 nests were recorded annually. The Utqiaġvik nests bore 3 to 10 sized-clutches with a mean of 6 eggs per nest and an annual mean hatching success from 39 to 91%. 31–87% of chicks were able to depart on foot and 48–65% were annually estimated to survive to fledge; elsewhere, 40% survived to fledge.<ref name= Holt/><ref name= Parmelee/> In another set, 97% of observed eggs both hatched and fledged.<ref name= Watson/> In Norway, the fledging success from 10 nests was much lower at about 46%.<ref name= Hagen/> Norwegian data, which previously indicated it to be an almost accidental breeder in northern Norway, indicates that it is a more regular breeder than expected, though. 3 good years were found for snowy owls between 1968 and 2005: 1974 (when there were 12 pairs), 1978 (22 pairs) and 1985 (20 pairs), with 14 additional locations when potential (but not confirmed) breeding has occurred.<ref name= Jacobsen/> The main determinable causes of nest failure were deemed to be [[starvation]] and [[Hypothermia|exposure]].<ref name= Holt/> A number of Norwegian and Finnish nests were known to fail due to severe [[black fly]] parasitism.<ref>Solheim, R., Jacobsen, K. O., Øien, I. J., Aarvak, T., & Polojärvi, P. (2013). ''Snowy Owl nest failures caused by blackfly attacks on incubating females''. Ornis Norvegica, 36, 1–5.</ref>', 12 => 'The snowy owl can live a long life for a bird.<ref name= Holt/> Records show that the oldest snowy owls in captivity can live to 25 to even 30 years of age.<ref name= Konig/><ref name= Holt/><ref>Schenker, A. (1978). Höchsalter europaischer Vögel im Zoologischen Garten Basel. Ornithol. Beob. 75: 96–97.</ref> Typical lifespans probably reach around 10 years in the wild.<ref name= Konig/><ref name= Mikkola/> The longest known lifespan in the wild was one that initially banded (possibly in its first winter) in [[Massachusetts]] and recovered dead in [[Montana]] 23 years and 10-month later.<ref name= Holt/> The annual survival rate for twelve females on [[Bylot Island]] was estimated at around 85–92.3%.<ref>{{cite journal|doi=10.1002/jwmg.414}}</ref> It is often reputed that snowy owls frequently died from starvation, with historical accounts frequently opined they "had to" leave their breeding grounds due to lemming "crashes" but would starve to the south.<ref name= Kerlinger/><ref name= Gross1/><ref name= Zettenberg>{{cite journal|doi=10.1898/NWN07-19.1}}</ref> However, it was proven fairly early on that snowy owls often do survive throughout the winter.<ref name= Bent/> This is reinforced somewhat by small radio-tracking and banding studies of the northern [[Great Plains]] and the intermountain [[valley]]s of the northwestern United States.<ref name= Zettenberg/><ref name= Kerlinger3>{{cite journal|doi=10.2307/1368844}}</ref> More circumstance evidence shows a lack of starvation in the eastern part of North America as well.<ref>{{cite journal|title=Winter irruptive Snowy Owls (''Bubo scandiacus'') in North America are not starving|doi=10.1139/cjz-2017-0278|url=https://www.researchgate.net/publication/322843463_Winter_irruptive_snowy_owls_in_North_America_are_not_starving}}</ref> There is evidence that some adults are known to return to the same wintering areas in ensuing years, areas which are far south of their breeding range.<ref>{{cite journal|doi=10.29173/bluejay1721}}</ref><ref>{{cite journal|author1=Follen, D. |author2= Luepke, K. |year=1980|title= Snowy Owl recaptures|journal= Inland Bird Banding |volume=52|pages= 60}}</ref> At Logan Airport, most snowy owls that are seen appear to be in good condition.<ref name= Holt/><ref name= Smith/> Of 71 dead snowy owls found in winter in the northern Great Plains, 86% died from assorted [[Major trauma|traumas]], including [[Roadkill|collisions]] with automobiles and other, usually manmade, objects as well as [[electrocution]]s and [[Culling|shootings]]. Only 14% of the 71 deaths were due to apparent starving. Data showed some owls appeared to incur injuries but healed and survived.<ref name= Kerlinger3/> More evidence was found in wintering snowy owls in New York of [[Bone healing|healed fractures]], though some may require surgery to recover.<ref>{{cite journal|pmid=30204018|title=Successful Management of Open, Contaminated Metacarpal Fractures in an Adult Snowy Owl (''Bubo scandiacus'') With a Minimal Type II External Skeletal Fixator}}</ref> 537 wintering birds in Saskatchewan were studied based on [[Fatty acid metabolism|fat reserves]], which were superior in females over males and adults over juveniles; while 31% of females lacked fat reserves, at least 45% of males found starving or in a state of infirmity were males and 63% turned into [[Wildlife rehabilitation]] centres were also males.<ref name= Chang/> In British Columbia, of 177 snowy owl deaths, of owls to die, only a small percentage were due to natural causes, such as assumed starvation at 13% and 12% were "found dead".<ref name= Campbell/> 1 fledgling on Fetlar dead due to [[pneumonia]] and ''[[Staphylococcus]]'' while a second died from ''[[Aspergillosis]]''.<ref name= Robinson/> Evidence shows that in Utqiaġvik during exceptionally prolonged rains (i.e. 2 to 3 days), nest-departed young in Utqiaġvik were vulnerable to starvation, leading to [[hypothermia]] and pneumonia.<ref name= Holt/> Due to their natural history, the snowy owl may be effected more severely by [[Parasitism|blood parasitism]] than other raptors, due to lowered [[Immunity (medical)|immunity]].<ref>{{cite journal|pmid=29517448|title=Clinical effect of hemoparasite infections in snowy owls (''Bubo scandiacus'')}}</ref> Conversely, they appear to have lower levels of ectoparasites like [[Mallophaga|chewing lice]] than in other large owls per large samples from [[Manitoba]]. The snowy owls averaged about 3.9 chewing lice per host against 7.5 for great grey owls and 10.5 for great horned owls.<ref>{{cite journal|doi=10.4039/tce.2019.42|title=Infestation parameters for chewing lice (Phthiraptera: Amblycera, Ischnocera) infesting owls (Aves: Strigidae, Tytonidae) in Manitoba, Canada}}</ref>', 13 => 'This species presence and numbers is dependent on amount of food available. In "lemming years", snowy owls can appear to be quite abundant in habitat.<ref name= Konig/> Numbers of snowy owls are difficult to estimate even within studies that take place over decades due to the nomadic nature of adults.<ref name= Holt/> The population of [[Scandinavia]] has long been perceived as very small and [[Ephemerality|ephemeral]] with Finland holding 0–100 pairs; Norway holding 1–20 pairs and Sweden holding 1–50 pairs.<ref name= Holt/><ref name= Jacobsen/><ref>Väisänen, R. A., Lammi, E., & Koskimies, P. (1998). ''Distribution, numbers and population changes of Finnish breeding birds''. Otava, Helsinki, Finland.</ref><ref name= Saurola>{{cite journal|doi=10.5253/078.097.0411}}</ref> A low breeding population within [[European Russia]] has been estimated to hold 1,300–4,500 pairs and Greenland to have 500–1,000 pairs.<ref>BirdLife International (2015). ''European Red List of Birds''. Office for Official Publications of the European Communities, Luxembourg</ref><ref>{{cite journal|doi=10.3312/jyio.44.1|title=Cross-species amplification of microsatellite markers in the Great Horned Owl ''Bubo virginianus'', Short-eared Owl ''Asio flammeus'' and Snowy Owl ''B. scandiacus'' for use in population genetics, individual identification and parentage studies}}</ref> Other than northern part of the American continent, a majority of the snowy owl's breeding range is in northern Russia, but overall estimates are not known.<ref name= Holt/><ref>Stepanyan, L.S. (1990). ''Konspekt ornitologicheskoi fauny SSSR. [Conspectus of the Ornithological Fauna of the USSR]''. Nauka, Moscow. (In Russian with English summary.).</ref> An exact count of 4,871 individuals were seen on surveys between the [[Indigirka River|Indigirka]] and [[Kolyma river]]s.<ref name= Potapov/> The numbers estimated by Partners in Flight and other authors by the 2000s was that North America held about 72,500 snowy owls, about 30% of which were juveniles.<ref>Rich, T. D., Beardmore, C. J. Berlanga, H., Blancher, P. J., Bradstreet, M. S. W., Butcher, G. S., Demarest, D. W., Dunn, E. H., Hunter, W. C., Iñigo-Elias, E. E., Kennedy, J. A., Martell, A. M.. Panjabi, A. O., Pashley, D. N., Rosenberg, K. V., Rustay, C. M., Wendt, J. S. & Will, T. C. (2004). ''Partners in Flight North American Landbird Conservation Plan''. Cornell Lab of Ornithology, Ithaca, NY, USA.</ref><ref>{{cite journal|doi=10.2193/0091-7648(2006)34[1392:EOFHOW]2.0.CO;2}}</ref> The Canadian population of snowy owls was estimated at 10,000–30,000 (in the 1990s) or even to 50,000–100,000 individuals, perhaps improbably.<ref>{{cite journal|author=Kirk, D. A., Hussell D. & Dunn, E. |year=1995|title=Raptor population status and trends in Canada|journal= Bird Trends|volume= 4|pages= 2–9}}</ref><ref>Reding-License, A. A. (2015). Harfang des neiges (''Bubo scandiacus''). Government of Canada.</ref><ref>American Ornithologists' Union (1998). ''Check-list of North American Birds, 7th edition''. American Ornithologists' Union, Washington, DC, USA.</ref> Within Canada, the population on [[Banks Island]] was once claimed at up to 15,000–25,000 in productive years and in [[Queen Elizabeth Islands]] at about 932 individuals.<ref name= Manning/><ref>Miller, F. L. (1987). ''Snowy Owl numbers on twelve Queen Elizabeth Islands, Canadian High Arctic''. Journal of Raptor Research 21 (4): 153–157.</ref> Alaska is the only state with breeding snowy owls but has probably quite a bit fewer breeding owls than does Canada.<ref>Alaska Department of Fish and Game. State of Alaska special status species 2011.</ref> Furthermore, the Partners in Flight and the [[IUCN]] estimated that the world population was roughly 200,000–290,000 individuals as recently as the 2000s.<ref>PIFSC. ''Partners in Flight Science Committee (2013)''. Population estimates database (Version 2.0) 2013. Available from http://rmbo.org/pifpopestimates.</ref><ref>BirdLife International. ''Nyctea Scandiaca''. 2006 IUCN Red List of Threatened Species (2004). Available from http://www.iucnredlist.org.</ref><ref>Burton, J. A. (1973). ''Owls of the world''. New York: E. P. Dutton.</ref> However, in the 2010s, it has been discovered that all prior estimates were extremely excessive and that more precise numbers could be estimated with better surveying, [[Phylogeography|phylogeographic data]] and more insights into the owl's free-wheeling wanderings.<ref name="iucn status 19 November 2021" /><ref name= Holt/> It is now believed that there are only 14,000–28,000 mature breeding pairs of snowy owls in the world.<ref name= Holt/><ref name= Marthinsen/> During lemming declines, the number of nesting females may drop down to as low as 1,700 worldwide, a dangerously low number, and the number of snowy owls worldwide is less than 10% of what it was once thought to be.<ref name= Holt/><ref name= Marthinsen/><ref>{{cite journal|doi=10.2307/1527}}</ref> Due to the small and rapidly declining population, the snowy was uplisted in 2017 to being a [[vulnerable species]] by the [[IUCN]].<ref name="iucn status 19 November 2021" /> A 52% decline has been inferred for the North American population since the 1960s with another even more drastic estimate placing the decline from 1970 to 2014 at 64%.<ref>Berlanga, H., Kennedy, J. A., Rich, T. D., Arizmendi, M. C., Beardmore, C. J., Blancher, P. J., Butcher, G. S., Couturier, A. R., Dayer, A. A., Demarest, D. W., Easton, W. E., Gustafson, M., Iñigo-Elias, E., Krebs, E. A., Panjabi, A. O., Rodriguez Contreras, V., Rosenberg, K. V., Ruth, J. M., Santana Castellón, E., Vidal, R. Ma. & Will, T. (2010). ''Saving our shared birds: Partners in Flight tri-national vision for landbird conservation''. Ithaca: Cornell Laboratory of Ornithology.</ref><ref>Rosenberg, K. V., Blancher, P. J., Stanton, J. C., & Panjabi, A. O. (2017). ''Use of North American Breeding Bird Survey data in avian conservation assessments''. The Condor: Ornithological Applications, 119(3), 594–606.</ref> Trends are harder to delineate in Scandinavia but a similar downward trend is thought to be occurring.<ref name= Holt/><ref name= Jacobsen/><ref name= Saurola/>', 14 => 'Snowy owls can be quite wary, as they are not infrequently hunted by [[Circumpolar peoples]].<ref name= Voous/> Historically, the snowy owl was one of the most persecuted owl species.<ref name= Holt/> In the irruption of 1876–77, an estimated 500 snowy owls were shot, with similar numbers in 1889–90 and an estimated 500–1,000 killed in [[Ontario]] alone during 1901–02 invasion and about 800 killed in the 1905–06 invasion.<ref name= Bent/> Indigenous people of the Arctic historically killed snowy owls as food but now many communities in northern Alaska are fairly modernized, therefore biologists feel that the permitted killing of snowy owls by the indigenous is outdated.<ref name= Holt/><ref>{{cite journal|url=https://brooklynworks.brooklaw.edu/bjil/vol30/iss2/6/|author=Bakalar, E. M. |year=2004|title=Subsistence Whaling in the Native Village of Barrow: Bringing Autonomy to Native Alaskans Outside the International Whaling Commission|journal= Brook. J. Int'l L.|volume= 30|pages= 601}}</ref> The consumption of snowy owls by humans has been proven as far back as ancient cave deposits in France and elsewhere, and they have even been considered as one of the most frequent food species for early humans.<ref>{{cite journal|url=https://www.researchgate.net/publication/285483173_La_chasse_aux_oiseaux_pendant_la_Prehistoire|author=Mourer-Chauviré, C. |year=1979|title=La chasse aux oiseaux pendant la Préhistoire|journal= La Recherche|volume= 106|issue=10|pages= 1202–1210}}</ref><ref>{{cite journal|doi=10.1016/J.QUAINT.2015.11.146|title=Hunting fast-moving, low-turnover small game: The status of the snowy owl (''Bubo scandiacus'') in the Magdalenian}}</ref> They do not shun developed areas especially with old field that hold rodents and, due to lack of human experience, can be extremely tame and unable to escape armed humans.<ref name= Voous/> In British Columbia, of 177 snowy owl deaths, the most often diagnosed cause of death was shootings at 25%, often well after legal protection of the species.<ref name= Campbell/> The number [[Poaching|poached]] snowy owls in Ontario is opined to be unusually high considering their scarcity.<ref name= Desmarchelier>Desmarchelier, M., Santamaria-Bouvier, A., Fitzgérald, G., & Lair, S. (2010). ''Mortality and morbidity associated with gunshot in raptorial birds from the province of Quebec: 1986 to 2007''. The Canadian Veterinary Journal, 51(1), 70.</ref> While the species was once otherwise killed as food and then later shot out of resentment for perceived threats against domestic and favored game stock, the reasoning behind ongoing shooting of snowy owls into the 21st century is not well-understood.<ref name= Holt/><ref name= Dufresne/><ref name= Desmarchelier/> Siberian snowy owls are frequently victim to [[Bait (luring substance)|baited]] [[Trapping|fox traps]], with possibly up to around 300 killed in a year based upon very rough estimates.<ref>{{cite journal|author=Ellis, D. H. & D. G. Smith|year=1993|title=Preliminary report of extensive Gyrfalcon and Snowy Owl mortality in northern Siberia|journal= Raptor-Link |volume=1 |issue=2|pages=3–4}}</ref> [[Warfarin]] poisoning in use as [[rodenticide]]s are known to kill some wintering snowy owls, including up to six at Logan Airport alone.<ref name= Campbell/><ref name= Smith/><ref>{{cite journal|author=Stone, W. B., Okoniewski, J. C. & Stedelin, J. R. |year=1999|pmid=10231745|title=Poisoning of wildlife with anticoagulant rodenticides in New York|journal= Journal of Wildlife Diseases |volume=35|pages=187–193}}</ref> [[Mercury (element)|Mercury]] concentrations, most likely through [[bioaccumulation]], have been detected in snowy owls in the [[Aleutian Islands]] but it is not known whether fatal [[mercury poisoning]] has occurred.<ref>{{cite journal|doi=10.1016/j.marpolbul.2014.02.034}}</ref> [[Polychlorinated biphenyl|PCB]]s may have killed some snowy owls in concentration.<ref name= Heggoy/> Some airports have advocated and instituted the practice of shooting owls to avoid birdstrikes but successful [[Wildlife translocation|translocation]] is possible and preferred given the species protected status.<ref name= Holt/><ref name= Smith/><ref name= Linnell/>', 15 => '[[Global warming|Climate change]] is now widely perceived to perhaps the primary driver of the snowy owl's decline. As temperatures continue to rise, abiotic factors such as increased rain and reduced snow are likely to effect lemming populations and, in turn, snowy owls. These and potentially many other issues (possibly including modifying migrating behavior, vegetation composition, increased insect, disease and parasite activities, risk of [[hyperthermia]]) are a matter of concern.<ref name="iucn status 19 November 2021" /><ref name= Holt/><ref name= Heggoy/><ref name= ACIA>ACIA. (2004). ''Impacts of a warming climate: Arctic climate impact assessment''. Cambridge: Cambridge University Press.</ref><ref>Inouye, D. W. (2019). "Climate change in other taxa". ''Effects of Climate Change on Birds'', p. 257. {{ISBN|9780198824268}}</ref> Additionally, reduction of sea ice, which snowy owls are now known to rely extensively on, as a result of warming climates, impacts could be significant.<ref name="iucn status 19 November 2021" /><ref name= Holt/><ref name= Marine/> The effect of [[climate change]] was essentially confirmed in northern Greenland where a perhaps irrevocable collapse of the lemming population was observed. From 1998 to 2000, the lemming numbers appeared to have quickly declined. The number of lemmings per hectare (ha) is less than one-fifth of what it once was in Greenland (i.e. from 12 lemmings per ha to less than 2 per ha at peak). This is almost certainly correlated with a 98% decline in owl productivity as well as that of the local [[Stoat|stoats]] (the [[long-tailed jaeger]] and [[Arctic fox]]es, though previously thought to be almost as reliant on lemmings, seem to be more loosely coupled and more generalized and did not decline as much).<ref name= Schmidt>{{cite journal|pmid=22977153}}</ref><ref>{{cite journal|doi=10.4080/gpcw.2011.0113}}</ref> The amount of lemming mounds is much less than it once in northern Greenland and any variety of [[population cycle]] has been apparently abandoned by what remains of the lemmings.<ref name= Schmidt/>' ]
All external links added in the edit (added_links)
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All external links in the new text (all_links)
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Whether or not the change was made through a Tor exit node (tor_exit_node)
false
Unix timestamp of change (timestamp)
1638346238
Retrieved from "https://en.wikipedia.org/wiki/Special:AbuseLog/31415295"