Sex differences in foraging ecology of the chick rearing Brünnich’s Guillemots (Uria lomvia) breeding in a High Arctic colony

Some seabirds, such as alcids exhibit sexual monomorphism, often displaying intersexual variation in parental investment and breeding ecology. In the Brünnich’s Guillemot (Uria lomvia), both sexes contribute to incubation and chick rearing. However, it has been found that females provide more meals to chicks older than two weeks, while males spend more time defending the nest and exclusively take care of fledglings after leaving the colony. In this study combining GPS-tracking and remote sensing, we investigated sex-specific foraging ecology of the chick-rearing Brünnich’s Guillemots breeding in the High Arctic (where sex differences are poorly recognized). We found that although both sexes performed foraging trips of similar characteristics, males foraged significantly closer to the colony (mean ± SD: 41.8 ± 23.11 km) in shelf zone with optimal foraging conditions (low sea surface temperature) compared to females exploring further located suboptimal foraging areas (high sea surface temperature, greater depths) (54.2 ± 20.85 km). By utilising more diverse habitats, females exploited a broader foraging habitat niche (defined by sea surface temperature, sea depth, and distance from the colony) than males. This study illustrates how females and males of monomorphic seabird species may adopt different foraging strategies to balance their investment during the chick-rearing period.