Don Edwards
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Canvasback, cont.

ducklings hatch, the females bring their broods to large ponds where they eat aquatic invertebrates. Females usually stay with the ducklings until they are almost ready to fly, but as many as 25% of the ducklings die before fledging in early August. The ducklings are dying as a result of predation by avian and mammalian predators and possibly largemouth bass, exposure when separated from hens, and severe weather.

This year, we plan to capture 60 female canvasbacks and implant them with radio transmitters with a 1-year life, so we may track the birds from Ruby Lake to their wintering areas on San Francisco Bay and back again. We hope to examine the distribution and movements of these radio-marked canvasbacks, determine their foraging areas and diet, and the bioaccumulation of contaminants on their wintering areas and its subsequent effect on their nesting success. With a little luck, we may find new information which improves our understanding of this species and provides a way to improve their populations across the seasons.

Kammie Kruse is a graduate candidate with the University of Wyoming, working at the San Francisco Bay Estuary Field Station of the U . S. Geological Survey, Biological Resources Division. Her research topic is the breeding biology of canvasbacks at Ruby Lake National Wildlife Refuge. John Takekawa is a research wildlife biologist and station chief at the field station which is co-located with San Pablo Bay National Wildlife Refuge on Mare Island in Vallejo. His research specialties include studies of the migration and wintering ecology of migratory waterbirds with radio telemetry, and biology of the San Francisco Bay estuary.