We analyzed the diets of 83 Ring-necked Ducks (Aythya collaris) collected on breeding areas in Beltrami County, Minnesota. Larval Trichoptera, Odonata, and Diptera, adult Hirudinea, and seeds from three plant genera, Zizania, Nuphar, and Potamogeton, formed most of the diets of hens during the breeding season. Males differed from females in the amounts and proportions of animal taxa consumed and in their diversity. Differences between the sexes increased during the breeding season. Consumption of animals by females increased significantly between prelaying and laying periods, while consumption by males changed little. We suggest that temporal diet shifts of female Ring-necked Ducks relative to males are a result of the higher protein requirements of females during prelaying and laying periods.