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Cooperation And Competition: Nepotistic Tolerance And Intrasexual Aggression In Western Bluebird Winter Groups, Janis L. Dickinson, Melody Euaparadorn, Katherine Greenwald, Chandreyee Mitra, Daizaburo Shizuka

Papers in Ornithology

Two hypothesized benefits of delayed dispersal are access to resources and prolonged brood care (or parental nepotism). Resource abundance (mistletoe wealth) is a key factor influencing whether sons stay home in western bluebirds, Sialia mexicana, but nepotism is also observed. Western bluebird sons commonly remain in their family groups throughout the winter, whereas daughters usually disperse before winter. Because pairing often takes place in winter groups, with newly formed pairs settling on exclusive all-purpose territories in spring, selection for sexual competition and nepotism co-occur and may simultaneously influence patterns of aggression within groups. We measured aggression at mealworm feeder …