Ecology and Management of Islands, Peninsulas and Structures for Nesting Waterfowl

Waterfowl Production on Nesting Islands in Mountain Meadows Reservoir, California

Virginia K. Getz
Jones & Stokes Associates, Inc.
1242 14th Avenue
Sacramento, California 95822

James R. Smith
Pacific Gas and Electric Company
3400 Crow Canyon Road
San Ramon, California 94583

In 1976 the California Department of Fish and Game constructed eleven nesting islands along the northern shoreline of Mountain Meadows Reservoir in northern California. We studied waterfowl nesting on these islands from March through July 1986 to determine waterfowl production and identify factors influencing productivity. Nests were located and nesting chronology was followed until the fate of all located nests and eggs were determined. Thirty-eight Canada goose (Branta canadensis moffitti) nests were located. Only 5% hatched successfully; 82% were destroyed by predation. Hatching success of eggs in successful nests was 40%. Forty-three duck nests were located. Of these nests, 40% hatched successfully and 44% were destroyed by predation. Hatching success of eggs in successful nests was 87%. Predation losses were primarily due to canids. Predation losses were greatest when reservoir elevations dropped, allowing canids to reach the islands. This study indicates that a combination of distance between island and shore of approximately 60-150 m and water depths of 0.6-1.0 m are required to reduce canid predation at Mountain Meadows Reservoir.

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