Behavioral Ecology and Sociobiology

, Volume 39, Issue 2, pp 71-76

Fattening strategies in dominance-structured greenfinch (Carduelis chloris) flocks in winter

  • Mikael HakeAffiliated withDepartment of Zoology, Section of Animal Ecology, University of Göteborg, Medicinaregatan 18, S-413 90 Göteborg, Sweden

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Abstract

Relationships between social status and levels of body reserves stored by members of greenfinch (Carduelis chloris) flocks in winter were investigated. In addition, the adjustment of reserves by birds of different rank to experimental changes in food predictability and to changed weather conditions were examined. Birds with low social status carried overall larger body reserves than high-ranked birds. The results of the experiments suggest that this was mainly because subordinates, due to their low priority to food access, perceived future foraging success as less predictable than dominants. In response to severe weather, which probably increased the risk of starvation for birds, dominants temporarily increased their reserves more than subordinates. This response also indicated that birds with low social status carried larger reserves than high-ranked birds, and demonstrated that dominants could increase food intake when there was a risk of energetic shortfall. The results suggest that fattening strategies in greenfinches depend on social status. In winter, subordinates may be forced to carry larger reserves than dominants to safeguard against social constraints in access to food during critical times. As body reserves may be costly to carry and acquire, this should reduce the probability of surviving the winter for subordinates compared to dominants.

Key words Winter fattening Social rank Body reserves Food predictability