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Marine Ecology Progress Series

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MEPS 382:211-219 (2009)  -  DOI:

Seabird seasonal trophodynamics: isotopic patterns in a community of Pacific alcids

W. E. Davies1,3, J. M. Hipfner1, K. A. Hobson2, R. C. Ydenberg1,*

1Centre for Wildlife Ecology, Simon Fraser University, 8888 University Blvd., Burnaby, British Columbia V5A 1S6, Canada
2Environment Canada, 11 Innovation Blvd., Saskatoon, Saskatchewan S7N 3H5, Canada
3Present address: Department of Ecology & Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario M5S 3B2, Canada

ABSTRACT: We measured δ15N and δ13C values in the blood of breeding adults and nestlings of 5 species of alcids at Triangle Island, British Columbia, to estimate the extent to which these seabirds alter their foraging ecology across successive breeding stages. Considerable intraspecific (stage-to-stage) and interspecific variation was found. Two species—common murre Uria aalge and pigeon guillemot Cepphus columba—fed consistently at high trophic levels (i.e. diets of fish) in inshore or benthically linked habitats. The foraging ecology of 3 others—Cassin’s auklet Ptychoramphus aleuticus, rhinoceros auklet Cerorhinca monocerata and tufted puffin Fratercula cirrhata—was more variable. Tufted puffins exhibited especially dramatic trophic and habitat shifts between early and late-season diets. With the exception of tufted puffin, the diet of provisioning adults differed from that fed to their nestlings. Trophic level of the community as a whole increased as the season progressed due to the combination of trophic shifting by rhinoceros auklets and tufted puffins, and earlier breeding by zooplanktivorous Cassin’s auklets than by piscivorous murres and guillemots. Our results contribute to a growing body of evidence that marine bird species exhibit considerable flexibility in their foraging behaviour and also shed new light on seasonal patterns in the trophic relations within marine bird communities.

KEY WORDS: Alcids · Breeding stages · 13C · Community ecology · Foraging ecology · 15N · Trophic relationships · Stable isotope analysis

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Cite this article as: Davies WE, Hipfner JM, Hobson KA, Ydenberg RC (2009) Seabird seasonal trophodynamics: isotopic patterns in a community of Pacific alcids. Mar Ecol Prog Ser 382:211-219.

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