724_Final Report.pdf - North Pacific Research Board

migration, or how the diets of juveniles and non-breeding adults compare with those of breeding adults or
chicks (Barrett et al. 2007). Because FAs provide information over a longer period of time, it may be
possible to get information about diets during non-breeding seasons (e.g., describe the diet during
migration by sampling birds at arrival to breeding sites). However, in order to do this, captive studies
must be performed to determine the period of time over which the diet can be back calculated. This non-
lethal technique of FA signature analysis may be particularly useful in estimating the diets of species of
conservation concern.
The spectacled eider Somateria fischeri and Steller’s eider Polysticta stelleri were listed as
threatened under the provisions of the U.S. Endangered Species Act in the 1990s (Federal Register 1993,
1997). Reasons for the population declines remain unknown, but changes in the marine environment and
available food resources may be limiting the recovery of both species (U.S. Fish and Wildlife Service
1996, 2002). Spectacled and Steller’s eiders use a range of marine habitats for staging, molting and
wintering (Petersen et al. 2000, Fredrickson 2001). Because eiders winter and stage in marine habitats, the
breeding outcome likely depends on availability of adequate marine resources, but information about
timing and sources of critical nutrient acquisition to reproduction is lacking for the threatened eider
species in the North Pacific. Also, the extent to which spectacled and Steller’s eiders use marine versus
terrestrial nutrients for reproduction is unknown. Determining the diet preferences and foraging habitat
associations of these eiders in relation to seasonal and life history stages will provide information to help
identify and characterize critical habitats of these threatened breeding populations. Our goal was to
validate QFASA to estimate the diets in captive spectacled and Steller’s eiders. We assessed the
quantitative characteristics of FA deposition and developed CCs for individual FAs to account for eider
lipid metabolism. We used simulation studies using the captive eider diet to evaluate the reliability with
which diet items could be distinguished in the model. Finally, we tested the model and CCs by estimating
the diets of experimentally fed captive eiders.
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