American Crow    Corvus brachyrhynchos

Migratory Status: Short-distance migrant

PIF Population Estimate: 31 000 000

Percent of western hemisphere population breeding in boreal forest: <25%

BAM Effective Detection Radius (m) : 211.17

PIF Maximum Detection Distance (m) : 400

Canadian BBS Population trend: 0.3 n.s. (-0.2 to 0.8)

Life History

The American Crow is one of the best-known and most recognisable bird species in North America. Having learned how to coexist with humans and thrive in urban settings, as well as in more natural open landscapes, it is also one of the most successful birds on the continent. A member of the highly inquisitive and intelligent Corvid family (crows, ravens, and jays), the American Crow is a black, medium-sized bird, with a slightly rounded tail. Males are slightly larger than females. Young birds (<15 months old) can be distinguished by the presence of a brownish tinge to their head and back feathers, versus the violet sheen of older birds.

American Crows breed throughout most of North America. In Canada, their breeding range extends from the southeastern portion of the Yukon, east across the Prairie Provinces and through Ontario and southern Quebec into the Maritimes, avoiding the most northern regions of the country. In the United States, breeding populations occur everywhere but exceptionally dry regions where the habitat becomes unsuitable. The winter range of the American Crow consists of much of the southern portion of its breeding range, primarily south of the Canadian border. Because of the overlap in breeding and winter range, most southern populations are considered non-migratory.

The range of the American Crow overlaps with the Northwestern Crow (C. caurinus) on the west coast of North America, and the Fish Crow (C. ossifragus) on the east coast. Where crow species overlap, they can be very hard to distinguish from one another in the field, but, in general the American Crow is larger than those other two species, and has a higher pitched, less nasal “caw”.

During the breeding season, mated pairs in migratory populations defend a nesting territory and raise young on their own. However, some non-migratory populations exhibit cooperative breeding, where helpers (generally young from the previous year) assist a mated pair with nest building and raising young. In this case, the ‘helpers’ forgo breeding for that season and stay on their natal territory for another year. Regardless of breeding strategy, during winter all crows join huge communal roosts that can contain thousands of individuals. Roosting sites often persist in the same general area and in some cases are well over 100 years old.

American Crows are omnivores and will eat almost anything, including seeds, fruits, eggs, small birds, amphibians, and carrion. They obtain most of their food while foraging on the ground. Instances of tools being used to assist with foraging (e.g. a piece of wood used to probe holes for grubs) have been documented in this species. Interestingly, while foraging in flocks, sentinels will often perch in surrounding trees to keep watch and send out an alarm to flock mates when predators or other dangers arise.

Reference(s)

Verbeek, N. A., and C. Caffrey. 2002. American Crow (Corvus brachyrhynchos), The Birds of North America Online, . A. Poole, Ed. Ithaca: Cornell Laboratory of Ornithology; Retrieved from The Birds of North America Online database: http://bna.birds.cornell.edu/bna/species/647