MEPS 466:233-247 (2012)  -  DOI: https://doi.org/10.3354/meps09916

ABSTRACT: Although seabirds search large areas for food, their distributions often correlate with physical characteristics of the marine environment that can serve to aggregate prey. Kittlitz’s murrelets Brachyramphus brevirostris are found almost exclusively in Alaskan waters, where they are closely associated with glacial fjords, suggesting that the distribution of this bird might be tightly linked to specific physical habitat characteristics of the fjords. We investigated relationships among locations used by Kittlitz’s murrelets, water column characteristics, and landscape features in Harriman Fjord and Heather Bay, Prince William Sound, Alaska, USA. In Harriman Fjord, Kittlitz’s murrelets were observed in shallow water near upwelling areas, indicated by a cold-water wedge near the surface (~10 m depth) in temperature-depth profiles. In Heather Bay, Kittlitz’s murrelets used locations closer to the glacial moraine than the average available habitat. The temperature-depth profiles at these locations showed a cold, fresh surface layer (near surface to 5 m depth); however, the temperature-depth profile variable was statistically insignificant, likely because of small sample size. Although the best temperature-depth profile variables were dramatically different between the 2 fjords, both of these glacially influenced water column characteristics may serve to concentrate prey at an optimal depth, allowing Kittlitz’s murrelets to focus their effort at predictable foraging locations. Given the widespread wasting of glaciers throughout their range, Kittlitz’s murrelets may face increased pressure as changes in water column dynamics within glacial fjords affect the distribution and concentration of preferred prey.

KEY WORDS: Brachyramphus brevirostris · Kittlitz’s murrelet · Seabird habitat use · Conductivity-temperature-depth meter · Temperature-depth profile · Water column profile · Glacial moraines · Case-controlled logistic regression