Jordan F. D. auteur aut IRD Shaffer S. A. auteur aut IRD Conners M. G. auteur aut IRD Stepanuk J. E. F. auteur aut IRD Gilmour M. E. auteur aut IRD Clatterbuck C. A. auteur aut IRD Hazen E. L. auteur aut IRD Palacios D. M. auteur aut IRD Tremblay Yann auteur aut IRD Antolos M. auteur aut IRD Foley D. G. auteur aut IRD Bograd S. J. auteur aut IRD Costa D. P. auteur aut IRD Thorne L. H. auteur aut IRD text journalArticle eng text/pdf reformatted digital access Understanding the at-sea movements of wide-ranging seabird species throughout their annual cycle is essential for their conservation and management. Habitat use and resource partitioning of Laysan (Phoebastria immutabills) and black-footed (Phoebastria nigripes) albatross are well-described during the breeding period but are less understood during the post-breeding period, which represents similar to 40% of their annual cycle. Resource partitioning may be reduced during post-breeding, when birds are not constrained to return to the nest site regularly and can disperse to reduce competitive pressure. We assessed the degree of spatial segregation in the post-breeding distributions of Laysan (n=82) and black-footed albatrosses (n=61) using geolocator tags between 2008 and 2012 from two large breeding colonies in the Northwestern Hawaiian Islands, Midway Atoll, and Tern Island. We characterized the species-and colony-specific foraging and focal distributions (represented by the 95 and 50th density contours, respectively) and quantified segregation in at-sea habitat use between species and colonies. Laysan and black-footed albatross showed consistent and significant at-sea segregation in focal areas across colonies, indicating that resource partitioning persists during post-breeding. Within breeding colonies, segregation of foraging areas between the two species was more evident for birds breeding at Tern Island. Spatial segregation decreased as the post-breeding season progressed, when spatial distributions of both species became more dispersed. In contrast to studies conducted on breeding Laysan and black-footed albatross, we found that sea surface temperature distinguished post-breeding habitats of black-footed albatrosses between colonies, with black-footed albatrosses from Midway Atoll occurring in cooler waters (3.6 degrees C cooler on average). Our results reveal marked at-sea segregation between Laysan and black-footed albatross breeding at two colonies during a critical but understudied phase in their annual cycle. The observed variation in species-environment relationships underscores the importance of sampling multiple colonies and temporal periods to more thoroughly understand the spatial distributions of pelagic seabirds. specialized habitat overlap distribution loggers movement ecology spatial ecology post-breeding segregation PACIFIQUE PACIFIQUE NORD 034 080 082 10 1028317 [18 p.] 2022 2296-701X https://www.documentation.ird.fr/hor/fdi:010086731 10.3389/fevo.2022.1028317 2296-701X [F B010086731] https://www.documentation.ird.fr/hor/fdi:010086731 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2023-02/010086731.pdf IRD - Base Horizon / Pleins textes 2023-02-08 2025-02-24 fdi:010086731 fre