Prey size selectivity by kelp gulls on Antarctic limpets at King George Island, Antarctica

Abstract

The present study was performed at Potter Peninsula (King George Island, Antarctica) with the following goals: (1) to assess the size selection of kelp gulls on Antarctic limpets during the chick-rearing period, and (2) to evaluate the degree of accuracy in the use of populational abundance and size-frequency distribution as an indicator of prey availability. The average size of limpets available to kelp gulls was significantly smaller than that of the population as a whole and those actually consumed by gulls. The odds ratio revealed a strong selectivity for large limpets, when available and consumed sizes were compared. However, only a proportion of the limpets present was available to gulls. These differences clearly show that using abundance information as an indicator of a resource importance can lead to substantial errors in ecological interpretations.