The influence of kinship on foraging competition in Siberian jays |
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Authors: | B Sklepkovych |
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Institution: | (1) Department of Zoology, University of Stockholm, S-106 91 Stockholm, Sweden Fax: +46-08-16 77 15; e-mail: bohdan@zoologi.su.se, SE;(2) Uppsala University, S-751 22 Uppsala, Sweden, SE |
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Abstract: | Foraging competition in Siberian jay groups was examined in relation to dominance and kinship to determine whether juvenile
offspring, by associating with adults, gained in food acquisition relative to juvenile immigrants. Members of the adult pair
were dominant over juvenile cohort members and males were dominant to females, although an inter-sexual hierarchy, with male
juveniles occasionally overlapping adult females, was suggested. Few competitive asymmetries were found between adults and
retained offspring or adults and immigrant juveniles when they were competing for food together, but in kin and non-kin foraging
groups, respectively. Male offspring visited the bait site more frequently than adult males, and female immigrants spent less
time at the bait site 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, although 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
that they control juvenile foraging. Although offspring benefit in the presence of adults, adults may incur a cost to their
restraint by spending more time at the bait site when competing with immigrants. These results extend conclusions from previous
work describing the role of selective tolerance by adults which relaxes competition with retained offspring in Siberian jay
winter groups. The present findings suggest that offspring benefit in both immediate and future energy gains, which may have
a direct influence on survival.
Received: 18 September 1996 / Accepted after revision: 26 January 1997 |
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Keywords: | Competition Dominance Foraging Kinship Perisoreus infaustus |
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