Diets of Ring-Necked Ducks Wintering on Catahoula Lake, Louisiana

Abstract

Ring-necked ducks (Aythya collaris) use lipid reserves accumulated on wintering and spring stopover areas to meet their subsequent reproductive requirements (Hohman, 1986; Hohman et al., 1988; Alisauskas et al., 1990). In 1989 midwinter surveys, 75% of ring-necked ducks observed in the Mississippi Flyway and 56% observed throughout the United States were in Louisiana (U.S. Fish and Wildlife Service, unpubl. data). Because numbers of ring-necked ducks counted in midwinter surveys at Catahoula Lake and the adjacent Catahoula National Wildlife Refuge have averaged 34,000 in recent years (Louisiana Department of Wildlife and Fisheries, unpubl. data), habitat conditions there could have a significant influence on the continental population of this species. We quantitatively describe diets of ring-necked ducks wintering on Catahoula Lake, a 12,000ha wetland basin located in the Mississippi River floodplain of central Louisiana (31030'N, 92008'W). Historically, the lake basin filled during late fall, and water levels generally remained high through June and then receded in July, exposing about 6,000 ha of mud flats by the first week of August (Wills, 1971). The annual cycle of drying and reflooding stimulated growth of moist-soil plants that attracted large concentrations of wintering waterfowl. In the 1960s, a navigation project on the Red River necessitated construction of a diversion canal and a water-control