The diet of the American crow consists mostly of invertebrates such as earthworms, grasshoppers, moth and butterfly larvae, beetles, and marine invertebrates (2) (3). An opportunistic feeder (3), the American crow also eats plant matter such as seeds, fruits and crops, as well as amphibians, reptiles, small birds and mammals, carrion, fish, crabs and gastropods (2) (3) (5). Its existence in inner city areas leads this species to also eat discarded human food (3), which it will occasionally harass people for (2).
The American crow mostly forages on the ground (3), although it also feeds along the edges of water bodies and in shallow water, using its bill to pick, probe, grab or dig for food (2) (3). When chasing prey or moving quickly on the ground, the American crow moves by hopping, with one foot hitting the ground slightly before the other (3). The American crow is known to drop certain types of prey out of the air onto a hard surface to crack their thick shells (2) (3). Excess food may be buried in a hole in the ground and retrieved at a later date (2) (3) (5).
A gregarious species, the American crow usually occurs in pairs or family groups and can form enormous flocks outside of the breeding season (2) (4) (5), with some winter roosts averaging around 200,000 birds (5). Large flocks of between 30 and 200 individuals, occasionally up to 1,000, are formed in the northern areas of the range for the southward migration between August and December. The return northern migration to the breeding grounds usually occurs between February and April (2) (3) (5).
The American crow is usually monogamous (2). The nest is built by both sexes between February and early June, and is usually well hidden in the high horizontal branches of a tree, typically close to the trunk. However, nests can sometimes also be found in bushes, buildings or telegraph poles (2) (3) (5). A new nest is built each year (3), and is composed of an outer layer of twigs, stuffed internally with bark, grass, stalks, animal hair, mud, roots, leaves and occasionally refuse (2) (3) (5). The nest of the American crow is usually solitary, although colonies are occasionally formed by some populations (5). Breeding pairs are occasionally known to allow one or more non-breeding individuals to live with them as ‘helpers’, to help defend the nest from predators and feed the young (2) (5).
The female American crow lays a clutch of four or five eggs between February and June, which are blue-green or pale olive, speckled brown and grey and are smooth and slightly glossy (3) (5). The female then incubates the eggs for between 16 and 18 days (2) (5), with the male and any ‘helpers’ bringing food to the nest (2) (3). When the eggs have hatched, the female also begins to forage for food (3) (5). Most fledging occurs between May and July (2), after which the young follow the male and female while they are foraging and learn how to catch prey (3). Some young remain within the territory of the breeding pair to act as ‘helpers’ in future breeding seasons, whereas others travel to join other flocks. Occasionally, the young American crows leave the natal territory but return in the following breeding season to assist the adults (2).
The American crow is known to live for up to 14 years in the wild and up to 59 years in captivity (2).