Birds
American Crow
Corvus brachyrhynchos · also called common crow
The American crow is the black bird you already know: cawing from a roadside tree, walking across a lawn, streaming across the evening sky toward a roost. It is also one of the most intelligent birds in North America, able to solve problems, use simple tools, and remember the face of a person who once wronged it.
Overview
Corvus brachyrhynchos is an all-black member of the crow family, about 45 cm long, with a fan-shaped tail and a flat, familiar caw. It lives across most of the United States and southern Canada in nearly every habitat that offers open ground for feeding and trees for nesting, and it eats an enormous range of foods, from insects and grain to carrion and rubbish.
Crow, not raven
The two are often confused. The common raven is much larger, with a wedge-shaped tail, a shaggy throat, a deep croak, and a habit of soaring. The American crow is smaller, flaps steadily, has a squared tail and a plain caw, and is far more tied to farms and towns.
A social, clever bird
American crows live in extended families: young often stay for years and help raise later broods. Outside the breeding season they form communal roosts of thousands. They recognise individual human faces, scolding and avoiding people who have trapped them years earlier and teaching that reaction to others, and they gather around dead crows in a way that seems to help them learn about danger.
Status
The American crow is Least Concern and increasing, having adapted well to human landscapes. The one sharp setback was West Nile virus, which arrived in 1999 and killed a large fraction of crows in affected regions before the population recovered.
American Crow: common questions
What is the difference between a crow and a raven?
In North America the common raven is clearly bigger, close to the size of a hawk, while the American crow is about pigeon-plus size. In flight a raven shows a diamond or wedge-shaped tail and long fingered wings and often soars and tumbles, whereas a crow has a squared or rounded fan of a tail and flaps steadily with few glides. The raven has a heavier bill, a shaggy set of throat feathers called hackles, and a deep, resonant croak or knocking call, while the crow gives the familiar flat caw. Ravens tend to travel in ones and twos in wilder country; crows are more social and more tied to farms and towns.
Can American crows really recognise individual humans?
Yes, this is one of the best-documented cases of face recognition in a wild animal. In a long-running study, researchers trapped and banded crows while wearing a distinctive mask, then walked around campus wearing either that mask or a different one. Crows scolded and mobbed the trapping mask for years afterward, even though those particular birds were never harmed again, and the response spread to crows that had not been present at the trapping, meaning the information was passed socially. Crows also remember people who feed them and will bring small objects to a reliable feeder.
Why do crows gather in huge numbers in winter?
They form communal roosts, and the reasons are thought to include safety in numbers against owls, warmth from packing together on cold nights, and information sharing, since a bird that fed poorly can follow better-fed neighbours to food the next morning. The roosts assemble every evening from a wide area, with birds funnelling in along traditional routes and often gathering first at staging sites before the final move to the roost trees at dusk. Large roosts in towns can become a nuisance through noise and droppings, and cities sometimes try to disperse them.
Are American crows a threat to songbirds?
Crows do eat the eggs and nestlings of other birds, and around a crow nest or a concentrated roost this predation can be locally noticeable. Across whole landscapes, though, studies generally find that crows are not a major driver of songbird declines, which are far more strongly linked to habitat loss, pesticides, cats, and collisions. Crows are opportunists taking a seasonal food source, and songbird populations evolved alongside them. Removing crows has rarely been shown to boost songbird numbers in a lasting way.