American Ornithologists' Union Annual Meeting, Cincinnati, OH, August 1995.
The dynamics of winter American Crow foraging flocks in New York state. Kevin J. McGowan, Section of Ecology & Systematics, Cornell University, Ithaca, NY 14853.
American Crows (Corvus brachyrhynchos) form large foraging aggregations in winter. Although flocks are common, movements of crows within and between flocks, and the extent of use of the flocks by permanently resident crows is largely unknown. I censused winter flocks of crows around Ithaca, New York for the presence of approximately 450 marked individuals of the local breeding population. Several large flocks (up to 300 crows) were present dependably in agricultural areas outside the city. Resident marked crows were observed in all the consistent flocks, including first-winter crows, older non-breeders, and territory-holding breeders. Although American Crows are cooperative breeders and maintain complex family social relationships, family members did not associate with each other in the large foraging flocks. Crows moved back and forth between home territories and the foraging areas during the day. Individuals were present in different flocks on different days, although some stability of membership in each flock was found. Distance from the home territory affected which flock the crows joined, with closer flocks preferred. Younger crows appeared to be the first to join large foraging flocks in fall, but on average, first-winter crows spent less time in the flocks than older non-breeders. These results indicate a variety of movement and association options are available to resident crows during the winter.