Foods of Lesser Scaups on Breeding, Migration, and Wintering Areas

Abstract

This food habits study was based on stomach contents of 164 lesser scaups (Aythya affinis): 39 from a breeding area in Manitoba, 88 from a fall concentration area on the Mississippi River in Illinois, and 37 from two wintering areas on the Louisiana coast. Animal foods made up the bulk of the diet of all three groups: 91.1 percent on the breeding area, 93.5 percent on the fall concentration area, and 63.7 percent on the wintering areas. The most important animal foods were amphipod crustaceans on the breeding area, molluscs on the fall concentration area, and fishes on the wintering areas. The percentages of animal foods are similar to those found in other recent investigations, but they differ from earlier findings which show the lesser scaup to be chiefly vegetarian. Additional collecting is needed, especially in early spring, for a more accurate picture of seasonal food habits but present information shows that lesser scaups feed chiefly, and sometimes almost exclusively, on animals most of the year. Animal foods decrease in the diet from summer to winter and probably reach a low point in late winter and early spring. Food habits data reflect the close relationship of the lesser and the greater scaup and show that they differ sharply from other North American members of their genus, which are chiefly vegetarians. A general picture of the food habits of the lesser scaup was given by Cottam (1939:38-46) who presented data on 1,051 stomachs from various localities in North America and reviewed the findings of earlier investigators. Since then, additional information has been obtained from scaups collected along fall migration routes (Korschgen 1955, Anderson 1959) and on wintering areas (Cronan 1957, Harmon 1962), but little attention has been given to food habits on the breeding ground. Munro (1941:134-137) reported the foods of 45 lesser scaups from British Columbia breeding areas. Cottam's (1939) data also included specimens from breeding areas but they were not discussed separately, except for 17 juveniles collected in western Canada. No information from other parts of the breeding range was found in the literature. This paper reports the foods eaten by adult lesser scaups on a breeding area in southwestern Manitoba, a fall concentration area on the Mississippi River in Illinois, and two wintering areas in Louisiana. Comparisons are made with previously published studies. Data from breeding and wintering areas were derived from 76 stomachs taken from specimens collected primarily for a study of the reproductive organs. Nineteen specimens in 1959 and 20 in 1960 were obtained in the pothole country around Erickson, Manitoba, during spring and summer. The other 37 were collected in marshes around Lake Borgne near New Orleans, Louisiana, in December, 1959 (20 specimens), and f om roadside ditches and ponds near Grand Chenier, southwestern Louisiana, in late February and early March, 1960 (17 specimens). Data from the fall concentration area are based on 88 stomachs taken from lesser scaups shot by hunters at Keokuk Pool on the Mississippi River, Hancock County, Illinois, during fall, 1948. Illinois specimens were provided by George C. Arthur, Illinois Department of Conservation, who generously contributed them to this study. The authors are in1 Contribution from the Gaylord Memorial Laboratory, the Delta Waterfowl Research Station, the Missouri Department of Conservation, and the Missouri Cooperative Wildlife Research Unit.