Winter Feeding Ecology of Scaup and Common Goldeneye in Michigan

Abstract

The feeding ecology of wintering greater scaup (Aythya marila), lesser scaup (A. affinis), and common goldeneye (Bucephala clangula) was studied on the Detroit River in southeast Michigan during 1980-81. Aquatic oligochaetes, wildcelery (Vallisneria americana), and pondweeds (Potamogeton spp.) were the principal foods consumed by all 3 species. Ducks foraged almost exclusively at sites with water depths -2 m. Macroinvertebrate densities were greater (P 31,000 in January and >16,000 in February. Waterfowl use of the Detroit River in winter is attributable to thermal and chemical discharges from power plants and factories that have increased amounts of ice-free water and to changes in current velocity in parts of the river caused by channel modifications. Maintaining winter shipping channels for transport of cargo would further open previously frozen habitats. Currently, there is little information available to develop effective management plans or to assess the effects of further alteration of wintering habitats. Temperature stress caused by low ambient temperatures could influence both survival and reproductive condition of waterfowl wintering at northern extremes of their range. Owen and Reinecke (1979) and Prince (1979) suggested energy expenditure for thermoregulation was high for waterfowl wintering at northern latitudes. Jorde et al. (1983) concluded that mallards (Anas platyrhynchos) were able to survive winters on Nebraska's Platte River by feeding on waste corn in nearby agricultural fields; however, this option is not available to diving ducks. Albright (1981) showed that body condition of female American black ducks (A. rubripes) wintering in Maine was adversely affected by low temperatures and wind chill. Habitat availability which was dependent on ice cover, also had an effect on condition of female black