Consistency pays: sex differences and fitness consequences of behavioural specialization in a wide-ranging seabird.

Specialists and generalists often coexist within a single population, but the biological drivers of individual strategies are not fully resolved. When sexes differ in their foraging strategy, this can lead them to different environmental conditions and stability across their habitat range. As such, sexual segregation, combined with dominance, may lead to varying levels of specialization between the sexes. Here, we examine spatial and temporal niche width (intraindividual variability in aspects of foraging behaviour) of male and female black-browed albatrosses (Thalassarche melanophrys), and its consequences for fitness. We show that females, where maximum foraging range is under fluctuating selection, exhibit more variable behaviours and appear more generalist than males, who are under directional selection to forage close to the colony. However within each sex, successful birds had a much narrower niche width across most behaviours, suggesting some specialization is adaptive in both sexes. These results demonstrate that while there are sex differences in niche width, the fitness benefit of specialization in spatial distribution is strong in this wide-ranging seabird.