Foraging and movement ecology of two sympatrically breeding Antarctic storm-petrels

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Storm-petrels are among the world’s most abundant pelagic seabirds, and thus form an important part of marine ecosystems. However, due to their small size and pelagic lifestyle, their trophic ecology is hard to study, especially during the non-breeding period which they spend on the open ocean. The trophic position and diet of black-bellied storm-petrels (Fregetta tropica) and Wilson's storm-petrels (Oceanites oceanicus) during the breeding period has been studied previously, revealing that BBSP forages at a higher trophic position consuming more fish than WSP. Additionally, stable isotope analyses (SIA) have shed some light upon their non-breeding movements. However, their non-breeding trophic position and distribution have so far remained understudied. In this project, we plan to build upon the body of work carried out over the past decades, and implement methods already proven successful in a pilot project and other petrel species. Using baseline-independent SIA, GPS and GLS tags, metabarcoding of diet contents and morphological and breeding parameter data collected during the breeding season on King George Island, Antarctica, we aim to further unravel the foraging and movement ecology of black-bellied and Wilson’s storm-petrels. We intend to use baseline-independent SIA to study the trophic position of the studied species both during and outside of the breeding period, for both adults and chicks, and to study how differences in observed diets and trophic position affect breeding success. We will equip adults with GPS tags during the breeding season to discover foraging ranges during the breeding period, and with GLS tags to study the non-breeding movements. We aim to test how differences in trophic positions between the species are connected to differences in distribution of the birds and their prey, how the foraging ecology changes among breeding seasons, and how it compares to the non-breeding season. As much of this information is still unknown, this study will set a baseline for future analyses of behavioural variability.