THE INFLUENCE OF KINSHIP ON FORAGING COMPETITION IN SIBERIAN JAYS

Foraging competition in Siberian jay groups was examined in relation t o dominance and kinship to determine whether juvenile offspring, by as sociating with adults, gained in food acquisition relative to juvenile immigrants. Members of the adult pair were dominant over juvenile coh ort members and males were dominant to females, although an inter-sexu al hierarchy, with male juveniles occasionally overlapping adult femal es, was suggested. Few competitive asymmetries were found between adul ts and retained offspring or adults and immigrant juveniles when they were competing for food together, but in kin and non-kin foraging grou ps, respectively. Male offspring visited the bait site more frequently than adult males, and female immigrants spent less time at the bait s ite than adult females. Under these circumstances, hoarding activities may limit the ability of alpha members to control resources. In mixed groups containing both juvenile offspring and juvenile immigrants, no difference was found in the number of visits made to the bait site, a lthough load sizes and foraging rates were lower for immigrant birds. Retained juveniles obtained greater load sizes and foraging rates when associating with adults. The social dominance of parents suggests tha t they control juvenile foraging. Although offspring benefit in the pr esence of adults, adults may incur a cost to their restraint by spendi ng more time at the bait site when competing with immigrants. These re sults extend conclusions from previous work describing the role of sel ective tolerance by adults which relaxes competition with retained off spring in Siberian jay winter groups. The present findings suggest tha t offspring benefit in both immediate and future energy gains, which m ay have a direct influence on survival.