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Marine Ecology Progress Series

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MEPS 357:291-299 (2008)  -  DOI:

Seasonal changes in diets of seabirds in the North Water Polynya: a multiple-indicator approach

Nina J. Karnovsky1,*, Keith A. Hobson2, Sara Iverson3, George L. Hunt Jr.4,5

1Pomona College, Department of Biology, 175 W. 6th St., Claremont, California 91711, USA
2Environment Canada, 11 Innovation Blvd., Saskatoon, Saskatchewan S7N 3H5, Canada
3Dalhousie University, Department of Biology, 1355 Oxford St., Halifax, Nova Scotia B3H 4J1, Canada
4University of California - Irvine, Department of Ecology and Evolutionary Biology, Irvine, California 92697, USA
5Present address: School of Aquatic and Fishery Sciences, Box 355020, University of Washington, Seattle, Washington 98195, USA

ABSTRACT: Each year, millions of seabirds migrate to the North Water Polynya, northern Baffin Bay, to feed in its productive waters during the 6 months that the polynya is free of ice. We evaluated seasonal shifts in diets of 3 species using the North Water: dovekie Alle alle, thick-billed murre Uria lomvia, and black-legged kittiwake Rissa tridactyla. Diets were assessed through a combination of stable isotope analysis of muscle tissue, fatty acid analysis of subcutaneous fat, and stomach content analysis. Dovekies had the lowest δ15N values and hence lowest trophic level in spring and summer, corresponding to their consumption of herbivorous copepods. In fall, their δ15N values increased as they switched to feeding at a higher trophic level on primary carnivores such as amphipods and fish. Throughout the study period, kittiwakes and murres had stomach contents and stable isotope values similar to dovekies in fall. Fatty acid signatures of black-legged kittiwakes and dovekies feeding in fall were similar, likely due to the reliance of both species on the pteropod Limacina limacina. Our study highlights the seasonal nature of prey availability and seabird diets in the polynya, as well as the utility of simultaneously using conventional stomach content analysis and stable isotope and fatty acid analyses to infer dietary patterns in marine food webs.

KEY WORDS: Diet assessment · Stomach contents · Stable isotope analysis · Fatty acid signatures · Seabird · Arctic · Polynya

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Cite this article as: Karnovsky NJ, Hobson KA, Iverson S, Hunt GL Jr. (2008) Seasonal changes in diets of seabirds in the North Water Polynya: a multiple-indicator approach. Mar Ecol Prog Ser 357:291-299.

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