724_Final Report.pdf - North Pacific Research Board

production (Parker & Holm 1990, Hario et al. 1999). Recent evidence suggests that some sea duck
species may employ mixed strategies where some of the nutrients required for successful breeding are
obtained from the nesting grounds (Hobson et al. 2005; Bond et al. 2007). 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 is lacking for the
threatened eider species in the North Pacific. During the nesting season, eiders feed on insects, insect
larvae, seeds, and plant materials in tundra ponds (Petersen et al. 2000, Fredrickson 2001), however, the
extent to which spectacled and Steller’s eiders use marine versus terrestrial nutrients for reproduction is
unknown. Understanding sources and timing of nutrient acquisition provides information for
characterization of critical habitats and conservation of the threatened breeding populations.
Traditionally, information on diets of marine birds has been collected by screening burrows to obtain
chick meals of puffins (Hatch & Sanger 1992); by various methods of live capture to cause adults and
chicks to regurgitate (Duffy & Jackson 1986); by visual identification to identify meals delivered to
chicks (Van Pelt & Shultz 2002, Litzow et al. 2002); and by collecting birds and determining stomach
contents by dissection (Petersen 1981, Duffy & Jackson 1986). There are several well-known problems
associated with these traditional methods (Barrett et al. 2007). Most methods employed in the past are
consumptive—vital meals are taken away from the adults or chicks, or the birds are sacrificed. Another
problem is that soft-bodied invertebrates or other food items that are not easily detected are often
inaccurately represented (Harrison 1984, Duffy & Jackson 1986). Hard food items that persist longer in
the digestive system are easier to identify than soft food items and can overemphasize the importance of
some prey items (Furness et al. 1984, Jobling & Breiby 1986). Moreover, each observation provides
information on only the most recent meal eaten, which may not represent the average diet. Also, eiders do
not provision food for ducklings on the nest. Indirect methodologies utilizing serum biochemistries have
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