Northern Prairie Wildlife Research Center
HABITAT: Breeds exclusively in shallow freshwater marshes and sloughs in the temperate prairie belt. Favors shallow wetlands up to 6 inches deep with bulrushes, cattails, whitetop, and common reeds, preferably near cultivated lands. In migration and in winter, inhabits sandy beaches, sandbars, fields, and pastures.
SPECIAL HABITAT REQUIREMENTS: Marshes and sloughs with sparse emergent vegetation no denser than one plant less than 3 feet tall per square foot.
NEST: Nests in colonies from a few hundred up to 50,000 pairs. Builds nests on masses of marsh vegetation, often floating on water and anchored to surrounding vegetation. Nests usually near open water.
FOOD: During the breeding season, forages in marshes and fields up to 30 miles from the nesting site. Feeds on a wide variety of foods, especially insects, also taking some amphibians; seeds of wheat, oats, and barley; a few small mammals; and in winter, fish and crustaceans.
REFERENCES: Clapp et al. 1983, Cramp and Simmons 1983, Guay 1968, Low and Mansell 1983, McAtee and Beal 1912.