Sexually distinct foraging strategies in an omnivorous seabird

Intra-specific differences in foraging behaviour can have fitness consequences, especially during breeding. We combined GPS tracking data from 34 lesser black-backed gulls (Larus fuscus) encompassing 2029 foraging trips with dietary information and morphometric measurements to test the effect of breeding status and sex as well as body size on foraging behaviour. We found sexually distinct foraging strategies in this generalist seabird, which were maintained throughout the breeding season. The larger males travelled further from the colony than females, spent more time offshore, and remained longer at the nest during nest bouts. Males fed mostly on fisheries discards at offshore trawlers with few alternative resources nearby. Females foraged predominantly on land or nearshore and in the Wadden Sea, where they had multiple foraging options. Individuals differed in foraging behaviour along a continuum of predominantly terrestrial to predominantly marine foragers. Foraging range, trip duration, and the proportion of time at sea increased with wing length. Our findings did not support the usual inference that sexual segregation is mediated primarily by differences in competitive strength as both sexes foraged substantially in competitive settings around fishing vessels, but in different habitats. Females accessed a wider variety of resources and a broad prey spectrum, by exploring a whole suite of foraging opportunities and habitats nearer the colony. Different behavioural strategies (a combination of individual specialisation and sexual segregation) during breeding could reduce intra-specific resource competition, competition between the sexes (and hence within a pair), or alternatively, reduce the risk of unbalanced food provisioning.