Canvasback (Aythya valisineria) and redhead (A. americana) productivity was studied at Ruby Lake National Wildlife Refuge in 1970, 71, and 77-82. Nest and egg success were high for both species. Canvasback clutch and brood sizes were lower than those reported from other areas, but because of high nest success and egg hatch rates the number of young produced per pair was high. Redhead clutch and brood sizes and productivity were within the range reported from other areas. Sixty-eight percent of all canvasback nests were parasitized by redheads. Productivity was affected by parasitism, spring weather and human disturbance. The effects of the weather and disturbance were not quantifiable.
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