Source and Additional Information

Animal Diversity Web
 
Cynthia Sims Parr
Some rights reserved

American crows have an unusual social system - they are cooperative breeders. This means that they may stay close to the place where they were born to help raise young and defend the area against predators. It is not well understood why these offspring do not obtain mates and raise their own families, but pairs with such helpers do not appear to be more successful at fledging offspring than those without helpers. Family members often preen each other (allopreening).

Most American crows defend large all-purpose territories. All members of the family assist in chasing predators away from the territory. Some individuals may remain on their territories during the winter, even if they participate in winter roosts or large flocks searching for food. Winter roosting behavior begins in autumn and peaks in mid-winter. Large numbers of crows, from tens to hundreds of thousands, will assemble in the late afternoon hours in an area with large trees. Often the flock will move from this area to a final roosting area at nightfall.

Some American crows migrate. Researchers have found marked crows from southeastern Michigan as far south as Tennessee, but more often migrants go shorter distances.

In addition to family groups and winter roosts, crows may join a third kind of social group called a floater flock. During the breeding season, floater flocks of up to 50 birds have been observed. Flock participants probably lack mates; at least some of these individuals also spend time on their natal territories as helpers. American crow floater flocks have not been well studied but in other species they allow individuals to roam an area finding mates or vacant territories while staying safely in a group.

American crows engage in a fascinating behavior called anting. A crow will position itself over an anthill and allow ants to scramble among its feathers, or it may pick up an ant and smear its feathers with it.

American crows are considered among the most intelligent birds, though there is little scientific evidence to prove this. American crows are resourceful in their food habits and are extremely difficult for researchers to capture in traps.

Communication and Perception

Source and Additional Information

Animal Diversity Web
 
Cynthia Sims Parr
Some rights reserved

American Crows are highly vocal birds. Unlike most other songbirds, males and females have the same songs. They have a complex system of loud, harsh caws that are often uttered in repetitive rhythmic series. Shorter and sharper caws called "kos" are probably alarm or alert calls. Slightly longer caws are probably used in territorial defense, and patterns of repetition may be matched in what may be considered "countersinging," or exchanges between territorial neighbors. "Double caws," short caws repeated in stereotyped doublets, may serve as a call-to-arms vocalization, alerting family members to territorial intruders. Sometimes pairs or family members coordinate their cawing in a duet or chorus. Harsher cawing is used while mobbing potential predators.

People are less familiar with the large variety of softer calls crows can make. Melodic, highly variable coos accompanied by bowing postures are used among family members, possibly as greetings or other bonding signals. Coos of cage-mates become similar over time; this vocalization may therefore be the basis of the mimicry ability shown by pet crows. Crows also give several kinds of rattles.

Young crows make gargling sounds that eventually turn into adult vocalizations. Yearling crows also "ramble" or run through long sequences of different patterns and rhythms of cawing.