Sex-specific chick provisioning and kleptoparasitism in the Least Frigatebird, Fregata ariel

Abstract

We examined sex-specific patterns of provisioning behaviour and kleptoparasitic host-use in the Least Frigatebird Fregata ariel. We aimed to determine, first, whether sex-specific kleptoparasitism, either at sea, or adjacent to the breeding colony, is an important source of food for chick provisioning and, second, whether observed behaviour is consistent with the expectation that sexual size-dimorphism in resource-poor environments consistently results in sex-specific divergence of foraging behaviour. We observed sex-specific differences in the time of day that adult frigatebirds provision chicks but no differences in the overall provisioning rate between sexes. We also observed no sex-specific kleptoparasitism via simultaneous monitoring of provisioning by Least Frigatebirds and Masked Boobies. Sex-specific differences in prey types attacked at the colony were observed, but these conflicted with predictions based on previous studies and were directly correlated with diural patterns of adult frigatebird attendance. Overall, we suggest that sexual differences in foraging behaviour in Least Frigatebirds are minimal and relate to either the use of different risk-sensitive foraging strategies by each sex, or are a consequence of body size differences in independently foraging sexes. While our results must be considered preliminary, we believe they provide justification for further critical examination of mechanisms of sex-specific behavioural divergence in seabird taxa.