RSPB Spotlight Crows

Contents

Meet the Crows

Ancestors and Relatives

An All-purpose Anatomy

Ultimate Omnivores

Crows at Home

The Cycle of Life

Intelligence and Communication

Crows and People

Glossary

Further Reading and Resources

Acknowledgements

Image Credits

Index

Meet the Crows

The black plumage, intelligent eyes and formidable bill of a Raven exemplify all that people most admire – and most fear – in corvids.

Love ’em or hate ’em, you certainly can’t miss ’em. The crows include some of Britain’s best-known, most abundant and most opinion-dividing birds. Clad mostly in black (with a couple of notable exceptions), they have a conspicuous appearance, which along with their confident habits and raucous voices makes them instantly identifiable. Sadly, familiarity can breed contempt: in towns, we tend to overlook crows as just part of the urban furniture; in the country, we have long accused them of damaging crops and harming livestock. In short, crows have an image problem – and this is unfortunate, as few birds are more rewarding of our attention.

What makes a crow?

The crow family is classified by scientists as the Corvidae and its members are known as corvids. As well as crows themselves, corvids include ravens, jackdaws, magpies, jays, choughs and other related species around the world. Many have a particularly close relationship with humans. Living alongside us, they have cemented themselves deeply within our culture, generating myths and folklore that are hundreds, or even thousands, of years old: for proof of this you need only look at our language, which is littered with expressions such as ‘scarecrow’ and ‘raven-haired’. As we have modified our landscapes over the centuries, clearing forests and building towns and roads, many corvids have taken advantage of the new opportunities, displaying a resourcefulness that allows them to thrive where most other birds decline.

Scientists who study corvids have discovered that these birds are among the most intelligent creatures on our planet. Indeed, their brain-to-body size ratio is the equal of any in the animal kingdom other than humans. In addition to their advanced capacity for tool use, problem solving, vocal communication and other skills, their behaviour also suggests an emotional range barely known outside the great apes and humans, including, for example, a capacity for grief and empathy (see here).

Carrion Crows adapt from an early age to the human environment.

Given these remarkable qualities, you might presume that corvids belong to some separate, ‘higher’ order of birds. In fact, they belong to the Passeriformes, the same order as thrushes, sparrows, finches, warblers and many other families of small bird – known collectively as passerines. Corvids are bigger than most of these relatives, however, with nearly all species being dove-sized or larger. Indeed, the Raven (Corvus corax) is bigger than a Common Buzzard (Buteo buteo) and is the largest of all the world’s passerines. Other features typical of corvids are their largely monochromatic plumage – most temperate species are either all black or black and white; the long wings of most species, adapted for powerful, agile flight; and a covering of fine feathers over their nostrils.

The success and intelligence of corvids come as part and parcel of their versatile lifestyle. These birds are generalists. In other words, rather than being adapted to specialise in feeding on a particular food – like finches with seeds, say, or swallows with flying insects – their robust, all-purpose bill allows them to enjoy a broad, omnivorous diet. This means they can adapt to a wide variety of food sources – and can continue to adapt as their environment changes around them, using their intelligence to exploit whatever new feeding opportunities arise.

This opportunistic Hooded Crow has captured a fish.

It is crows’ appetites that largely explains the bad press they receive. In farmland, species such as Rooks (Corvus frugilegus) may gather in large numbers to feed on cereal crops, which does not endear them to some farmers – although the birds also hoover up agricultural pests in the process. During the breeding season, species such as Carrion Crows (Corvus corone) and Magpies (Pica pica) also turn predator on eggs and nestlings, which does not go down well with some gamekeepers, nor with lovers of garden birds. Meanwhile, many people find the appetite of corvids for roadkill and other carrion unappealing – even though, like all scavengers, they provide an invaluable natural clean-up service. The birds’ reputation was not enhanced in bygone days when, during times of war and disease, human corpses were also sometimes on the menu.

Feeding, however, also illustrates some of the most impressive qualities of crows. These include a variety of problem-solving techniques, including using a selection of tools and in some cases even fashioning their own. Many species, notably Jays (Garrulus glandarius), are also habitual hoarders, collecting and caching food in secret hideaways, and then demonstrating prodigious powers of memory when they later retrieve it for consumption. This penchant for collecting and hiding explains the popular reputation of certain species, notably Magpies, for thieving.

Rooks are the most sociable of UK corvids, often gathering in enormous numbers.

Most corvids are highly sociable birds. Some, such as Rooks, nest in large colonies and many gather in large flocks outside the breeding season. These assemblages encompass a range of complex social behaviours. Individuals use a broad vocabulary of calls and body language to observe hierarchies, convey messages about food, warn their companions of danger and establish pair-bonds. They are capable of both assisting and deliberately deceiving one another, and some species even play games – such as ‘king of the mountain’ and ‘follow my leader’ – that appear to have no immediate practical function other than diversion.

Male and female corvids are similar in appearance and hard to distinguish from one another in the field. Most species establish monogamous pair-bonds and, like the majority of other passerines, are stick nesters, generally building their nests high in trees or on cliff ledges, depending on what their habitat offers. They lay anything from three to 10 eggs, the number varying both by species and by conditions. Incubation lasts around 20 days in most species, with the young fledging around four weeks later. Some corvids may live for upwards of 20 years in the wild, with records from some captive birds far exceeding that.

British crows

The British Isles are home to eight species of corvid, a figure that represents 6.6 per cent of the world’s 120-odd species. Most are either common or very common – only one, the Chough (Pyrrhocorax pyrrhocorax), is rare – and all range far beyond our borders across the northern hemisphere. Six species have largely glossy black and black-and-grey plumage: the Carrion Crow and its close northern relative the Hooded Crow (Corvus cornix), the Rook, the Raven, the Jackdaw (Corvus monedula) and the Chough. Distinguishing these can sometimes be a little tricky – although, with experience, the distinctive behaviour and appearance of each can be recognised. Two others, the Magpie and Jay, are strikingly different. A ninth species, the Nutcracker (Nucifraga caryocatactes), is a rare visitor from eastern Europe that occasionally turns up on our shores during harsh winters further east.

UK corvid populations

The table below lists the most recent estimates of corvid breeding populations in the UK, as published by the Avian Population Estimates Panel in September 2019. The figures are collated from numerous conservation sources and represent extrapolation from trends as well as actual counts. For species where actual nests can be counted, figures are given in pairs. For others, they are given as occupied breeding territories. Populations of all British corvids are currently increasing and thus may have risen slightly since these estimates were released. Overall populations are highest immediately after the breeding season when young have fledged.

*The Chough population rises to 433 pairs when the Isle of Man is included.

Carrion Crow

Corvus corone

The Carrion Crow is the definitive corvid.

This species – commonly known simply as the Crow – is the definitive corvid, with its strutting walk, all-black plumage, strong flight and signature caw. It is common and conspicuous in pretty much every corner of the British Isles, except for the far north-west of Scotland, the Isle of Man and much of Ireland, where it is replaced by its very close relative, the Hooded Crow. A medium-large bird with a powerful bill, it measures 45–47cm (17.5–18.5in) in length and has a wingspan of around 1m (3ft). This makes it much larger than a Jackdaw, Blackbird (Turdus merula) and Starling (Sturnus vulgaris), the other all-black species you might also meet in an urban park or garden.

Carrion Crows aren’t confined to urban settings, however, and range across virtually all habitats, from mountains and beaches to forest and farmland. In the last of these, they are often confused with Rooks (see here–here). The latter tend to be more gregarious, but this is not a foolproof distinction, as Carrion Crows may also gather in flocks outside the breeding season. A good look at a Carrion Crow, however, whether alone or in a crowd, should confirm its identity. It appears neater and less shaggy than a Rook, and lacks the Rook’s bare face and peaked cap. It also has a less pointed bill, and generally shows a greenish rather than bluish gloss to its black plumage.

This species is the ultimate generalist, feeding on insects, worms, grain, fruit, eggs, small vertebrates (including rodents, frogs and even ducklings) and, of course, carrion. It will pursue and harass other predators, from Foxes (Vulpes vulpes) to large raptors, to exploit their kills, and has adapted to feed on human waste, on high streets, in back gardens and in landfill sites. Through this last habit the Carrion Crow has grown tame and apparently fearless, and it will often snatch whatever it can find from under our noses – competing with the likes of gulls and Feral Pigeons (Columba livia) for the best pickings.

Carrion Crows establish a large breeding territory and generally build their bulky stick nest in a tall tree, although they may also use cliff ledges and old buildings. In early spring, the female lays 3–4 greenish eggs, blotched with brown, which she incubates alone for 18–20 days. The young fledge after 29–30 days, and offspring from one year may stay with their parents the following year to help them raise the next brood.

This species is found across much of central Europe, although