MEPS prepress abstract  -  DOI: https://doi.org/10.3354/meps12979

Breeding together, feeding apart: sympatrically breeding seabirds forage in individually distinct locations

Ellie Owen*, Ewan Wakefield, Paul Hollinrake, Alan Leitch, Laura Steel, Mark Bolton

*Email: ellie.owen@rspb.org.uk

ABSTRACT: Individuals can specialise such that mutually exclusive home ranges arise and the acquisition of site familiarity early in life can favour individual site fidelity in mature animals. Non-territorial Individual Foraging Site Fidelity (IFSF) has been reported frequently and, among seabirds, foraging theory predicts that IFSF is more likely in short-ranging, benthic-foraging species, because their prey occur predictably at small scales. We tracked 17 adult and 2 immature black guillemots Cepphus grylle (mean mass 406 g, median of individual maximum foraging range 4.3 km). Individuals consistently returned to the same feeding areas, such that IFSF was significantly greater than the null expectation at spatial scales of 0.1 to 5 km and did not decay significantly over 10 d. Immature birds ranged more widely than adult birds. Our study demonstrates that space use varies between individuals and that processes or threats occurring within the foraging range of a given colony may act disproportionately on some individuals rather than be equally distributed across a population. This finding contributes to a growing body of research on IFSF, which may have important implications for species management.