Animal Behavior Society Annual Meeting, Binghamton, New York, May 1990.
VIGILANCE AND GROUP SIZE IN THE AMERICAN CROW.
Kevin J. McGowan, Section of Ecology & Systematics, Cornell University, Ithaca, New York.
American Crows (Corvus brachyrhynchos) forage solitarily, in pairs or extended family groups, and in large flocks. I investigated the function of flocking by examining the vigilance of foraging crows in flocks of different sizes. Other studies have related flocking to predator detection by showing that individual vigilance decreases with increasing group size. American Crow scanning rates went down with increasing flock size, but the total amount of time foraging crows were vigilant actually increased. These results suggest that group formation in crows is for purposes other than predator detection, possibly for the enhancement of food acquisition or for socialization.