Abstract Understanding resource partitioning and niche segregation is crucial for explaining coexistence among seabirds. During the breeding season, colonial seabirds, such as storm-petrels, act as central-place foragers and face strong competition for resources. This study focused on intersexual niche segregation and interspecific differences in two sympatric storm-petrel species, the Black Storm-petrel ( Hydrobates melania ) and Leach’s Storm-petrel ( H. leucorhous chapmani ), breeding on San Benito Oeste Island (28°18’12” N, 115°35’24” W), Baja California, Mexico, in the Eastern Pacific. Fieldwork was conducted during the chick-rearing period in 2022. Foraging movements and main foraging areas of chick-rearing adults were determined by GPS tracking, and prey composition was identified using DNA metabarcoding of faeces and regurgitate samples. The results show that intersexual segregation differed between species and was not equally evident across niche dimensions. In Leach’s storm-petrels, molecular diet analysis revealed no evidence of dietary segregation between sexes. In Black Storm-petrels, by contrast, the sexes showed a tendency towards dietary differences, accompanied by sex-specific differences in foraging movements. Furthermore, the findings indicated distinct resource partitioning strategies between species: Black Storm-petrels primarily foraged in neritic waters, whereas the single tracked Leach’s Storm-petrel used oceanic waters. In addition, gastrointestinal parasites were documented for both species. This study contributes to the understanding of niche segregation in colonial seabirds and highlights the importance of integrating spatial and dietary components when studying resource partitioning in avian communities.
Schäfer et al. (Tue,) studied this question.