Risk-Sensitivity and Foraging Groups

Several recent studies reveal that foraging animals select resources in response to the probability distributions of rewards obtained and costs expended, rather than the expected values alone. This paper suggests that both the mean and variance of an individual bird's foraging time may depend on flock size. If individuals prefer to avoid variation in foraging time while exploiting a patchy environment, flocking should often be favored. Even subordinate birds, which acquire less than the average amount of food when a patch is discovered, may reduce foraging time variation by flocking. Individuals prefering greater variation, in order to achieve a very small foraging time, should feed as solitaries or seek smaller flocks than do birds which avoid variation.