The Evolution of Group Territorial Behavior and Cooperative Breeding

Abstract

Group territorial behavior and cooperative breeding are now recognized as widespread phenomena among birds of warm-temperate, subtropical and tropical climates. Ecological factors which cause selection for group territorial behavior are considered to be high adult survival and saturation of suitable habitat, modified by the demands of different feeding strategies. Cooperative breeding is viewed as a consequence of group territorial behavior, and a nonmathematical model is presented which predicts that maximum positive assistance by nonbreeders to the reproductive success of the breeding pair should occur in situations where it would not otherwise increase the fitness of the breeders to allow nonbreeders to remain within their territory. A decrease in the per capita reproductive rate of group territorial species, compared with similar pair-territorial species, is regarded as a by-product of the social system, not a specific adaptation.