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MEPS 429:291-301 (2011)  -  DOI:

Exploiting the closest productive area: geographical segregation of foraging grounds in a critically endangered seabird

M. Louzao1,2,*, J. Navarro3, M. G. Forero4, J. M. Igual1, M. Genovart1, K. A. Hobson5, D. Oro1

1Institut Mediterrani d’Estudis Avançats IMEDEA (CSIC-UIB), Miquel Marquès 21, 07190 Esporles, Mallorca, Spain.
2Helmholtz Centre for Environmental Research-UFZ, Permoserstraße 15, 04318 Leipzig, Germany
3Institut de Ciències del Mar (CSIC), Passeig Marítim de la Barceloneta 37–49, 08003 Barcelona, Spain
4Departamento de Biología de la Conservacíon, Estación Biológica de Doñana (CSIC), Apartado 1056, 41013 Sevilla, Spain
5Environment Canada, 11 Innovation Blvd., Saskatoon, Saskatchewan S7N 3H5, Canada

ABSTRACT: While breeding, seabirds are limited to exploiting resources within a restricted area around their breeding site and should exploit the closest productive marine areas within their distribution range. We investigated this hypothesis in one of the most endangered European seabirds, the Balearic shearwater Puffinus mauretanicus (ca. 3200 breeding pairs), restricted to the Balearic Islands. Our aims were (1) to assess whether isotopic evidence (i.e. stable isotopes of δ13C and δ15N) of foraging habitat partitioning occurs among northern, central and southern populations, (2) to geographically locate population-specific potential foraging grounds along the Iberian continental shelf, and (3) to assess whether oceanographic conditions could explain observed patterns of stable isotopes (SI). SI values showed a latitudinal gradient, with birds from the northern population having lower δ15N and δ13C values than central and southern populations. Potential foraging grounds of northern, central and southern populations were centred in Cape Creus, Ebro Delta and Cape La Nao, respectively, results which were supported by habitat models. Oceanographic conditions in each potential foraging ground were different; the northern population used richer, colder and deeper waters compared to the central and southern populations. Chlorophyll a was the main oceanographic variable that explained variation in SI values. We hypothesised that SI differences among Balearic shearwater populations might be a consequence of differences in baseline isotopic values among potential foraging grounds rather than real differences in diet. Our comprehensive study also provides important information for management strategies to conserve this critically endangered shearwater.

KEY WORDS: Balearic shearwater · Geographical foraging ground segregation · Habitat modelling · Mediterranean Sea · Oceanography · Puffinus mauretanicus · Stable isotopes

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Cite this article as: Louzao M, Navarro J, Forero MG, Igual JM, Genovart M, Hobson KA, Oro D (2011) Exploiting the closest productive area: geographical segregation of foraging grounds in a critically endangered seabird. Mar Ecol Prog Ser 429:291-301.

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