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Aquatic Biology

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AB 8:221-235 (2010)  -  DOI:

Oxygen stores and foraging behavior of two sympatric, planktivorous alcids

Kyle Hamish Elliott1,*, Akiko Shoji2, Kevin L. Campbell1, Anthony J. Gaston2,3

1Department of Biological Sciences, 190 Dysart Road, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
2Department of Biology, University of Ottawa, 30 Marie Curie, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
3Environment Canada, National Wildlife Research Centre, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada

ABSTRACT: Seabird species with overlapping diets commonly coexist at breeding colonies. For example, ancient murrelets Synthliboramphus antiquus and Cassin’s auklets Ptychoramphus aleuticus are similar-sized small alcids that feed on krill and small fish. Little is known regarding their partitioning of aquatic resources, so we assessed the O2 stores and foraging behavior of sympatrically breeding populations of these species. The attachment of recorders (1 to 3% of body mass) caused substantial nest desertion, but we reduced these effects by only equipping experienced birds early in the day. Auklets and murrelets had 18 to 24% higher mass-specific O2 stores than slightly larger non-diving kittiwakes Rissa tridactyla. When compared to published values, blood hemoglobin content was higher, muscle pH buffering capacity was similar and muscle myoglobin content was lower for small divers than for larger non-phocid divers. The slightly higher O2 stores of Cassin’s auklets was reflected in their aquatic behavior, as auklets dived longer than murrelets at any given dive depth. Moreover, chick-rearing auklets spent 31% more time underwater than incubating auklets and 50% more time underwater than incubating murrelets. In total, 45% of dives by chick-rearing auklets, 36% of dives by incubating auklets and 13% of dives by incubating murrelets exceeded their estimated aerobic dive limits. Murrelets primarily used V-shaped dives while auklets generally exhibited W-shaped dive profiles with a protracted bottom phase. Thus the O2 stores and foraging behavior of the 2 sympatric seabirds differed.

KEY WORDS: Cassin’s auklet · Ptychoramphus aleuticus · Ancient murrelet · Synthliboramphus antiquus · Reef Island · Haida Gwaii · Hemoglobin · Myoglobin

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Cite this article as: Elliott KH, Shoji A, Campbell KL, Gaston AJ (2010) Oxygen stores and foraging behavior of two sympatric, planktivorous alcids. Aquat Biol 8:221-235.

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