Parent–offspring dietary segregation of Cory’s shearwaters breeding in contrasting environments

In pelagic seabirds, who often explore distant food resources, information is usually scarce on the level of trophic segregation between parents and their offspring.\udTo investigate this issue, we used GPS tracking, stable\udisotopes and dietary information of Cory’s shearwaters\udCalonectris diomedea breeding in contrasting environments.\udForaging trips at Selvagem Grande (an oceanic island)\udmainly targeted the distant African coast, while at Berlenga\udisland (located on the continental shelf), shearwaters foraged mainly over nearby shelf waters. The degree of isotopic segregation between adults and chicks, based on\udd13C, differed markedly between the two sites, indicating\udthat adult birds at Selvagem fed their chicks with a mixture\udof shelf and offshore pelagic prey but assimilated more\udprey captured on coastal shelf waters. Isotopic differences\udbetween age classes at Berlenga were much smaller and\udmay have resulted from limited dietary segregation or from\udage-related metabolic differences. The diet of shearwaters\udwas also very different between the two colonies, with\udoffshore pelagic prey only being detected at Selvagem\udGrande. Our findings suggest that spatial foraging constraints influence resource partitioning between pelagic\udseabirds and their offspring and can lead to a parent–offspring dietary segregation