724_Final Report.pdf - North Pacific Research Board

ABSTRACT
The spectacled eider Somateria fischeri and the Alaska-breeding population of Steller’s eider Polysticta
stelleri were listed as threatened under the provisions of the U.S. Endangered Species Act in the 1990s.
Potential threats to the recovery of these populations include changes in the marine environment and
available food resources. However, relatively little is known of foraging ecology, nutritional
requirements, and food limitation in eiders. Quantitative fatty acid (FA) signature analysis (QFASA)
provides a minimally invasive method for studying foraging ecology in marine birds. Our goal was to
determine dietary FA deposition and calibration coefficients (CCs) for captive spectacled eiders (N = 8)
and Steller’s eiders (N = 8) for QFASA. From the long-term feeding period, we assessed the quantitative
characteristics of FA deposition and developed CCs for individual FAs to account for eider lipid
metabolism. Our results revealed that QFASA accurately estimated diet and diet switches in captive
eiders. QFASA also confirmed that complete FA turnover of the new introduced diets was not complete
by 21 or 29 days, and that diets could be estimated over > 29 days. Thus, our understanding of diet can be
back-tracked to more than a month in a feeding eider. We conclude that applying QFASA techniques to
eiders in the wild has the potential to provide valuable information about foraging ecology and habitat
associations of threatened populations.
KEYWORDS: Diet assessment technique, fatty acid analysis, Steller’s eider, spectacled eider, Polysticta
stelleri, Somateria fischeri, captive validation
CITATION: Wang, S.W., T.E. Hollmén, S.J. Iverson. 2009. Estimating diets of two species of threatened
sea ducks, the Steller’s eider (Polysticta stelleri) and the spectacled eider (Somateria fischeri): validation
of novel diet assessment techniques. North Pacific Research Board Final Report 724, 56 p.
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