Sexual segregation in the foraging distribution, behaviour, and trophic niche of the endemic Boyd’s shearwater (Puffinus lherminieri boydi)

Abstract

Studies on sex-speci c segregation in foraging and trophic niche have been focused on large and dimorphic seabirds, with less information on small monomorphic species. Here, we used mini-GPS loggers, habitat suitability models, and stable isotopes to assess the foraging movements, at-sea spatial distribution, and trophic ecology of male and female Boyd's shearwaters Pu nus lherminieri boydi in Raso Islet (16°36' N, 24°35' W), Cabo Verde, during the breeding seasons of 2018-2019. The existence of sexual foraging segregation was tested in short and long foraging trips. Females engaged on longer foraging trips, travelling towards more distant and northward regions from the colony when compared to males, especially during long foraging excursions. Spatial overlap within and between sexes was generally low, indicating a sex-speci c pattern in the foraging behaviour and spatial distribution of adult breeders. Habitat suitability models revealed a higher importance for chlorophyll a concentration in explaining females' at-sea distribution during long foraging trips when compared to males, although the most important predictors in explaining adults' distribution were sea surface temperature and height for short and long excursions, respectively. Stable isotope analysis revealed that both sexes occupied similar isotopic niches and stable isotope mixing models revealed no diet differences. This indicates that Boyd's shearwaters segregate at the spatial level while foraging but rely on similar food resources. Our results suggest that female-biased nutritional requirements at the onset of chick-rearing may be driving sexual foraging segregation in this population, which depends upon resources from a rather oligotrophic environment.