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Factors Influencing the At-Sea Distribution of Cassin's Auklets (Ptychoramphus aleuticus) That Breed in the Channel Islands, California - Factores que Influencian la Distribución Marina de Individuos de Ptychoramphus aleuticus que Anidan en las Islas del Canal en California
Josh Adams, John Y. Takekawa, Harry R. Carter and Julie Yee
Vol. 127, No. 3 (July 2010), pp. 503-513
Published by: American Ornithological Society
Stable URL: http://www.jstor.org/stable/10.1525/auk.2010.09273
Page Count: 11
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Abstract. We used radiotelemetry to evaluate at-sea habitat use by Cassin's Auklets (Ptychoramphus aleuticus) that bred at Prince Island, off southern California, from 1999 through 2001. We used logistic regression to compare paired radiotelemetry (presence) with random (pseudo-absence) location-associated habitat variables derived from (1) satellite remote-sensing of sea surface temperature and chlorophyll-a concentration and (2) bathymetry. Compared with random locations within their foraging area and after controlling for distance to colony, odds ratios indicated that Cassin's Auklets with dependent young occurred in relatively shallower, warmer, and chlorophyll-rich water associated with chlorophyll fronts near the insular shelf break. These oceanographic features characterize habitats that support key euphausiid prey (e.g., Thysanoessa spinifera) and also other krill predators. Radiotelemetry combined with satellite remote-sensing of the ocean provides an alternative to vessel-based surveys for evaluating seabird foraging habitats. In the absence of information on the actual distribution, abundance, and, hence, availability of zooplankton prey for seabirds, environmental factors can serve as proxies to help elucidate distributional patterns of seabirds at sea.
The Auk © 2010 American Ornithologists' Union