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Marine Ecology Progress Series

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MEPS 607:221-236 (2018)  -  DOI:

Foraging ecology of tropicbirds breeding in two contrasting marine environments in the tropical Atlantic

Ngoné Diop1,2,*, Laura Zango2, Annalea Beard3, Cheikh Tidiane Ba1, Papa Ibnou Ndiaye1, Leeann Henry3, Elizabeth Clingham3, Steffen Oppel4, Jacob González-Solís2

1Department of Animal Biology, Cheikh Anta Diop University, Av Cheikh Anta Diop, Dakar 5005, Senegal
2Institut de Recerca de la Biodiversitat (IRBio) and Department de Biologia Evolutiva, Ecologia i Ciències Ambientals (BEECA), Universitat de Barcelona, Av Diagonal 643, Barcelona 08028, Spain
3Marine Section, Environmental Management Division of the Environmental and Natural Resources Directorate, St Helena Government, Essex House, Jamestown STHL 1ZZ, St Helena Island, South Atlantic
4RSPB Centre for Conservation Science, The David Attenborough Building, Pembroke Street, Cambridge CB2 3QX, UK
*Corresponding author:

ABSTRACT: Studying the feeding ecology of seabirds is important not only to understand basic aspects of their ecology and threats but also for the conservation of marine ecosystems. In this regard, tropical seabirds have been relatively neglected, and in particular the trophic ecology of tropicbirds is scarcely known. We combined GPS tracking, environmental variables and sampling of regurgitates during incubation and brooding to understand the feeding ecology of red-billed tropicbirds Phaethon aethereus as well as how foraging strategies may change between 2 contrasting marine environments: a coastal island in the Canary Current upwelling (Îles de la Madeleine) and an oceanic island in the middle of the south Atlantic (St Helena). Tropicbirds breeding on the Îles de la Madeleine headed west, foraging on and beyond the shelf slope, probably to associate with subsurface predators which bring pelagic fish close to the surface. Birds from St Helena showed a greater foraging effort and a strong attraction to areas with the greatest species richness of Scombridae, possibly due to a greater difficulty in finding prey in the oligotrophic oceanic waters. Tropicbirds ranged much beyond the extension of the protected areas around their colonies, indicating that current protected areas are insufficient for these populations. We found no evidence to suspect direct mortality of tropicbirds in regional fisheries, but overexploitation of small epipelagic fish and tuna may decrease feeding opportunities and lead to competition with fisheries. The substantial differences in foraging behaviour demonstrated by individuals from both colonies indicates that caution should be taken when extrapolating foraging patterns of tropical seabirds breeding in contrasting oceanographic environments.

KEY WORDS: Foraging area · Foraging behaviour · Contrasting environmental features · Red-billed tropicbirds · Phaethon aethereus · Eastern tropical Atlantic · Protected areas · Diet · GPS tracking

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Cite this article as: Diop N, Zango L, Beard A, Ba CT and others (2018) Foraging ecology of tropicbirds breeding in two contrasting marine environments in the tropical Atlantic. Mar Ecol Prog Ser 607:221-236.

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