Abstract
Sexual segregation is common in many species and has been attributed to intra-specific competition, sex-specific differences in foraging efficiency or in activity budgets and habitat choice. However, very few studies have simultaneously quantified sex-specific foraging strategies, at sea distribution, habitat use, and trophic ecology. Moreover, these studies come from low latitude areas reflecting a lack of evidence for polar species. We investigated sexual segregation in snow petrels Pagodroma nivea and combined movement, foraging trip efficiency, stable isotope and oceanographic data to test whether sexual segregation results from sex-specific habitat use. Breeding birds foraging in the Dumont d’Urville sea, Antarctica, were tracked during incubation. Space-use sharing and utilization distribution were similar between males and females indicating no spatial segregation. Males and females foraged more in waters ≈400 m deep and less in waters deeper than ≈1000 m. There was no difference in δ13C values between males and females. Females foraged less than males in areas with higher sea ice concentration (SIC >70%) and had lower δ15N values in plasma, blood cells and feathers. Male and female foraging trip performances (trip duration, length, speed and directions, mass gain, proportion mass gain) were similar, but foraging efficiency (proportionate daily mass gain while foraging), was greater for females than for males, and was greater for larger females with deeper bills. Females were more efficient than males during short (<2 days) foraging trips. For females, but not for males, mass gain, proportion mass gain and body condition at return from a foraging trip were positively correlated to SIC of the foraging areas. Together, these results indicate that sexual segregation in snow petrels during incubation is mainly driven by habitat segregation between high (>70%) more profitable SIC and low SIC areas, probably driven by intra-specific competition.