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

Abstract

Studies on sex-specific segregation in foraging behaviour and trophic niche have been focussed 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 sex differences in the foraging movements, spatial distribution, and trophic ecology of Boyd’s shearwaters Puffinus lherminieri boydi in Raso Islet (16°36’ N, 24°35’ W), Cabo Verde, during the chick-rearing periods of 2018–2019. The existence of sexual foraging segregation was tested in short (< 1 day) and in long trips (≥ 1 day). Females engaged in slightly longer and more distant foraging trips, reaching northerly regions when compared to males, although sex differences were more pronounced during short trips. Spatial overlap within and between sexes was low, indicating a sex-specific pattern, albeit slight, in the foraging behaviour and spatial distribution of adult breeders. Habitat suitability models revealed a higher contribution of sea surface temperature and height for short and long trips, respectively, and regardless of sex. Stable isotope analysis revealed that both sexes occupied similar isotopic niches and the mixing model revealed no diet differences. In the absence of sexual size dimorphism, these findings may indicate that differential energetic demands may not manifest in strong differences in foraging behaviour or prey preferences, however, may be perceptible in differences in provisioning behaviour. Thus, it is possible that other factors involving distinct parental investment in chick-provisioning, such as the sensitivity to chick begging, could help explain the occurrence of sexual segregation in Boyd’s shearwater.