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Marine Ecology Progress Series

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MEPS 414:293-302 (2010)  -  DOI:

Geographic and seasonal variability in the isotopic niche of little auks

Jérôme Fort1,*, Yves Cherel2, Ann M. A. Harding3, Jorg Welcker4, Dariusz Jakubas5, Harald Steen4, Nina J. Karnovsky6, David Grémillet1,7

1Centre d’Ecologie Fonctionnelle et Evolutive, UMR 5175 du CNRS, 1919 Route de Mende, 34 293 Montpellier cedex 5, France
2Centre d’Etudes Biologiques de Chizé, UPR 1934 du CNRS, 79360 Villiers-en-Bois, France
3Environmental Science Department, Alaska Pacific University, 4101 University Drive, Anchorage, Alaska 99508, USA
4Norwegian Polar Institute, Polar Environmental Centre, 9296 Tromsø, Norway
5Department of Vertebrate Ecology and Zoology, University of Gdańsk, Legionów 9, 80-441 Gdańsk, Poland
6Department of Biology, Pomona College, 175 W. 6th St, Claremont, California 91711, USA
7Percy FitzPatrick Institute, DST/NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, South Africa

ABSTRACT: The non-breeding season of seabirds is extremely challenging to study because it is often spent offshore under harsh environmental conditions. We used stable isotope analysis to investigate little auk Alle alle feeding ecology throughout the annual cycle. The geographic distribution of little auks in the Arctic covers a wide range of oceanographic conditions. We sampled birds from 5 different colonies located in the most important breeding areas (Greenland and Spitsbergen) to examine how individuals breeding in contrasting marine environments differ in their trophic niche throughout the year. We found differences in summer δ15N values among the colonies, suggesting different target species despite low overall δ15N values in blood, which indicates a diet that is primarily composed of copepods. A rise in δ15N values between summer and autumn indicated that adults changed their trophic status to feed at a higher trophic level. During autumn, a large overlap in feather δ13C values between colonies suggests a common moulting area off Northeast Greenland. During winter, the isotopic signatures show that the trophic status of Greenland and Spitsbergen birds differed, with birds from Greenland feeding at low trophic levels (probably mostly on copepods), and birds from Spitsbergen maintaining a higher trophic level. These findings highlight contrasting seasonal and regional diet in little auk populations, and reveal possible population overlaps during the autumn moult. We found substantial trophic variability in little auks, which may indicate unsuspected capabilities to adapt to current, drastic environmental change in the North Atlantic.

KEY WORDS: Alcid · Annual cycle · Copepod · Diet · North Atlantic · Pelagic ecosystem · Seabird · Stable isotopes

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Cite this article as: Fort J, Cherel Y, Harding AMA, Welcker J and others (2010) Geographic and seasonal variability in the isotopic niche of little auks. Mar Ecol Prog Ser 414:293-302.

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