Northern Prairie Wildlife Research Center
HABITAT: Primarily inhabits small, shallow, fresh or slightly alkaline lakes and ponds, preferably without broad margins of emergent or floating aquatic vegetation, in mixed coniferous-deciduous woodlands north and west of the Great Plains. Logs, stumps, rocks, open shore, and sometimes fence rails near water are used for resting and loafing. Winters in sheltered marine habitats, or on brackish or freshwater.
SPECIAL HABITAT REQUIREMENTS: Tree cavities excavated by woodpeckers, especially northern flickers, near shallow, fertile waters in forested regions.
NEST: Prefers to nest in aspen trees near water containing unaltered northern flicker holes, but will also use pileated woodpecker holes. Also nests in Douglas-fir, balsam poplar, black cottonwood, ponderosa pine, and a few other coniferous and deciduous trees. Nests generally within 75 feet of water and rarely in dense forest. In some areas, accepts nest boxes 7 inches in diameter and 16 inches deep with entrances 2 7/8 inches wide.
FOOD: Prefers to forage in shallow water, diving to depths of 6 to 10 feet for food which is primarily animal material. In summer, mostly eats aquatic insects and larvae, but also includes water boatmen, shrimplike amphipods, some snails and small fishes, and seeds of pondweeds and naiads. During winter, mostly eats shrimp, snails, and other crustaceans.
REFERENCES: Erskine 1971, Johnsgard 1975b, Palmer 1976b, Terres 1980.