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Trans-equatorial migration links oceanic frontal habitats across the Pacific Ocean: year-round movements and foraging activity of a small gadfly petrel

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Brooke, M de L 


jats:titleAbstract</jats:title>jats:pGadfly petrels are among the widest-ranging birds and inhabit oceanic regions beyond the legislative protection of national jurisdictions (the High Seas). Detailed information on breeding phenology, at-sea distributions, and habitat requirements is crucial for understanding threats and designing conservation measures for this highly threatened group. We tracked 10 Stejneger’s petrels jats:italicPterodroma longirostris</jats:italic>, endemic to Isla Alejandro Selkirk, Juan Fernández Islands in the southeast Pacific Ocean, with geolocator-immersion loggers over two years to examine year-round movements, phenology, habitat use, and activity patterns. Birds conducted round-trip trans-equatorial migrations of 54,725 km to the northwest Pacific Ocean between Hawaii and Japan. Across the boreal summer, birds followed the jats:italicc.</jats:italic> 1000 km northward movement of the North Pacific Transition Zone Chlorophyll Front, before their return migration which took a long detour south toward New Zealand before heading east at 40–50°S, presumably benefitting from Antarctic circumpolar winds. To our knowledge, a comparable triangular migration is unique among seabirds. During the pre-laying exodus, birds traveled southwest to the Sub-Antarctic Front, and unlike congeners, there was no evidence of sexual segregation. Foraging areas during incubation were similar to pre-laying, with trips lasting 13 d and taking birds up to 4810 km southwest of the colony. Petrels spent > 75% of their time flying during breeding and migration, yet flight activity was substantially lower during non-breeding, presumably due to flight feather molt. Birds spent 87% of their time at sea within the High Seas and their apparent preference for oceanic frontal regions demonstrates the importance of protecting these remote habitats.</jats:p>


Acknowledgements: We would like to thank James Fox at Migrate Technology for advice and help with device management, Danilo and Guillermo Araya for crucial on-island support, the owner and crew of Tio Lalo for inter-island transport and Iva Vasquez and Valentina Colodro of Oikonos plus Jose Luis Cabello and María José Vilches of Island Conservation for logistical support. We thank Associate Editor Vitor Paiva and two anonymous reviewers who provided useful comments on an earlier version of the manuscript, John Horsfall for facilitating COVID-19-impeded transit through continental Chile, and Samantha Andrzejaczek for providing guidance on the preparation of one of the figures.


3109 Zoology, 3103 Ecology, 31 Biological Sciences, 15 Life on Land

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Marine Biology

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Springer Science and Business Media LLC
National Geographic Society (NGS-59743R-19)