| Summary: | As a basis for an effective, long-time program of management for the waterfowl of the Mississippi Flyway, detailed information about the diet of ducks that migrate through Illinois was considered essential. In the autumns of 1938, 1939, and 1940, duck gizzards totaling 4,977 were collected from hunting clubs and individual hunters at 21 sites along the Illinois River between Ottawa and Florence and 11 sites along the Mississippi River between Rock Island and Quincy. The following 17 duck species were represented: mallard, pintail, green-winged teal, blue-winged teal, baldpate, gadwall, shoveler, black duck, wood duck, lesser scaup, ring-necked duck, redhead, canvasback, ruddy duck, greater scaup, common goldeneye, and oldsquaw. The analyses indicated that, during the fall, most species of ducks in Illinois are predominantly vegetarians, that most of them feed principally on native wild plants, and that the lesser scaup is the only species with a diet predominantly animal. Of the 95 wild plants and 4 cultivated plants found in the gizzards and identified to species, the following 19 were most important: corn, rice cutgrass, marsh smartweed, coontail, wild millet, longleaf pondweed, red-rooted nut-grass, waterhemp, nodding smartweed, buttonbush, large-seeded smartweed, nut-grass, chufa, Walter's millet, sago pondweed, duckpotato, river-bulrush, teal grass, and giant bur-reed. Snails and mussels provided the largest animal food volume and occurred in the largest number of gizzards. Insects were second in volume and occurrence. More than 200 of the gizzards examined contained lead shot pellets that had been ingested.
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