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

• Published in: Marine ecology. Progress series (Halstenbek) Vol. 357; pp. 291 - 299
• Main Authors: Karnovsky, Nina J., Hobson, Keith A., Iverson, Sara, Hunt, George L.
• Format: Journal Article
• Language: English
• Published: Inter-Research 07-04-2008
• Subjects: Alle alle; Birds; Copepoda; Diet; Fatty acids; Gastrointestinal secretions; Isotopes; Limacina; Marine; Polynyas; Rissa tridactyla; Sea birds; Seasons; Signatures; Trophic levels; Uria lomvia; ANW, Atlantic, Baffin Bay; ANW, Atlantic, Baffin Bay, North Water Polynya
• ISSN: 0171-8630; 1616-1599
• DOI: 10.3354/meps07295

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: dovekieAlle alle, thick-billed murreUria lomvia, and black-legged kittiwakeRissa 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 pteropodLimacina 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.