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 sea- sonal 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 δ 15 N values and hence lowest trophic level in spring and summer, corresponding to their consumption of herbivorous copepods. In fall, their δ 15 N 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.
Highlights
The North Water is the largest and most productive Arctic polynya or seasonally ice-free body of water (Fig. 1)
We examined seasonal differences in stable isotope values, fatty acid composition, and stomach contents of 3 species of seabirds to understand the seasonal dynamics of energy flow in the North Water Polynya
Fatty acid signature analysis tissue was enriched compared to spring and summer values
Summary
The North Water is the largest and most productive Arctic polynya or seasonally ice-free body of water (Fig. 1). An estimated 33 million pairs of dovekies Alle alle (hereafter ‘dovekies’) breed along the western coast of Greenland adjacent to the North Water (Egevang et al 2003). These small subsurface feeders dive up to 35 m (Falk et al 2000). Black-legged kittiwakes Rissa tridactyla (hereafter ‘kittiwakes’) are surface feeders that make shallow dives (estimated population 30 000 pairs; McLaren 1982) These 3 species represent the vast majority of seabirds in the polynya’s food web and encompass a diversity of feeding guilds
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