Tracing Sources of Nutrients and Energy for Clutch Formation by White-winged Scoters

Project Number: 45

Year Funded: 2005

Lead Institution(s): Simon Fraser University

Project Lead: Dan Esler

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Collaborator(s): Stuard Slattery (DUC), Jean-Michel DeVink (USask), Eric Anderson (UW), James Lovvorn (UW), Cindy Swoboda (USask), David Safine (UAF)

Location: Pacific Flyway

Focal Species: White-winged Scoter (Melanitta delgandi)

Project Description: In waterfowl, the egg synthesis stage of reproduction is particularly challenging, requiring large amounts of nutrients and energy over a relatively short period. Because waterfowl are diverse in morphology, distribution, behavior, and diet, considerable interspecific (and even intraspecific) variation exists in reliance on endogenous reserves for clutch formation. A study of prairie-nesting WWSC used proximate analyses to reveal that nutrients for egg production were primarily derived from dietary sources; endogenous reserves were used to a lesser extent during incubation. However, more recent studies on related species have indicated that relying only on proximate analyses without directly tracing nutrient pathways can produce misleading results. Also, this previous study did not consider birds from multiple breeding locations.

We are identifying important habitats for WWSC by determining where and when females acquire nutrients for reproduction. This is important because (1) the reasons for scoter declines are unknown; (2) WWSC strategies for nutrient acquisition are unclear; (3) acquisition and allocation of nutrients for reproduction have been linked to waterfowl productivity; and (4) this work will result in clear implications for management of habitats that contribute to WWSC productivity. In conjunction with related studies, samples of adult female reserves and reproductive tissue, as well as key prey items, were collected in 2004 and 2005 in three breeding areas.