This cunning, inquisitive, vocal opportunist is one of the most widespread of North American birds. Everybody knows crows. You may have seen one pilfering the dog's food, tearing holes in your garbage bag, or emptying a temporarily neglected lunch bag. It is a mistake to underestimate a crow's ability. Most people have opinions about crows that run the gamut from outright hatred to bemused admiration.
Very similar in appearance to the Northwestern Crow (Corvus caurinus), this species is larger, has a higher-pitched voice, and is less social during the breeding season. The American Crow is also similar in appearance to the Fish Crow (Corvus ossifragus), which is smaller and has a distinct nasal voice. Where American Crow overlaps Northwestern Crow (e.g., Puget Sound, Washington) and Fish Crow (Atlantic seaboard and southeastern U.S.), identification is difficult, with voice the most reliable character.
American Crows are found in a wide variety of habitats, particularly in open landscapes, with scattered trees and small woodlots. Clearing of hardwood and coniferous forests, planting of trees around prairie homesteads and urban centers, and tilling of agricultural land has created additional habitat for the species, which is now more abundant than it was when the first European settlers arrived. Large-scale persecution during the nineteenth century and first half of the twentieth made crows shy of people. They learned quickly, however, that there is safety from guns in villages and cities and that food is abundant there.
Crows roost communally; often the same sites are used year after year. Outside of the breeding season, such roosts may contain thousands of local individuals, their numbers often augmented by migrants from northern regions. When these roosts are located in cities, they may become a nuisance requiring management.
Many people have contributed to what is known about this species. L. Kilham summarized his many publications, plus additional information, in book form ( Kilham 1989 ). Studies of breeding biology show that in some populations crows breed cooperatively; parents are assisted by auxiliaries (primarily young of the previous year or years) in raising young (Kilham Kilham 1984 , Kilham 1989 ; Chamberlain-Auger et al. 1990 ; Caffrey Caffrey 1992 , Caffrey 1999 , Caffrey 2000a ; McGowan 2001a ). An omnivorous diet ( Hering 1934 , Kalmbach 1939b , Platt 1956 ), with food mostly obtained on the ground, implies that almost everything edible is welcome. This includes the eggs and young of other species and certain agricultural crops. Many studies have dealt with ways of reducing economic losses caused by crows; see Johnson and Altman 1983 for a good summary.
Although much has been published about this crow, we still know relatively little about it—what individuals do and say, and why, over both the short (days) and long term (the lives of individuals, generations within populations). For example, why do some young become helpers and others not, even in the same population? Considering the near continent-wide distribution of the species, involving different habitats and climates, one might expect regional differences in social organization and breeding biology. Thus, statements in the account that follows may not necessarily pertain throughout the species' range. To answer many types of questions, one needs color-banded individuals, but crows are notoriously hard to capture, let alone recapture. One should keep in mind that several studies cited here (among others, Black 1941 ; Kilham Kilham 1984 , Kilham 1989 ) drew conclusions about social organization, breeding biology, and other topics based on unmarked birds.