Foods of Lesser Scaup and Blue-Winged Teal in the Saskatchewan River Delta

Abstract

The food habits of adult lesser scaup (Aythya affinis) and blue-winged teal (Anas discors) were compared through analysis of monthly samples of gullet contents in an area of typical breeding habitat in the Saskatchewan River Delta. Lesser scaup consumed an average of 66 percent animal food and 34 percent plant food, whereas blue-winged teal used animal and plant foods in nearly equal amounts. Significant changes in the proportions of plant and animal foods occurred between months; they appeared to be correlated with changing abundance of food items. Major foods of lesser scaup were invertebrates and aquatic seeds abundant throughout the shallow eutrophic lakes of the Delta. Main foods of blue- winged teal were snails and seeds of emergent and other marsh plants associated chiefly with the lake shorelines. These differences in the diets reduce competition between the two species and contribute to their ecological separation within the habitat. Water levels constantly held high to increase duck nesting success will not diminish the food supply for scaup but, in the long run, will be detrimental to the food supply for teal. This paper compares the diets of adult lesser scaup and blue-winged teal, the most abundant diving and dabbling ducks in a marsh complex in the Saskatchewan River Delta. The data were obtained as part of a larger study of the capability of that area to support wildlife production and the fea- sibility of intensive wildlife management within an integrated land-use project (Dir- schl et al. 1967). Very little information is yet available on the food habits of adult ducks on the breed-