This large dabbling duck breeds in a variety of North American wetlands, including freshwater wetlands created by beaver (Castor canadensis); brooks lined by speckled alder (Alnus incana); lakes, ponds, and bogs throughout mixed hardwood and boreal forests; and salt marshes. Postmolting males, females, and fledged young assemble near breeding areas in early September. Southward movements of migrants begin in September to early October, depending on latitude, and individuals travel overland or follow major rivers and the Atlantic Coast to reach wintering sites in coastal marshes from Nova Scotia to the mid-Atlantic states. Migrants eat seeds, foliage, and tubers of aquatic plants and seeds and fruits of terrestrial species, a variety of invertebrates, agricultural grains, and occasionally fish and amphibians.
This duck begins nesting in February in southern parts of its range, but often not until late May in northern parts. Most pairs form, or re-form, pair bonds annually in winter, many by December, and males defend territories until their mates reach mid-incubation. Nest sites are abundant and variable, and nests usually are well concealed and on the ground, often in uplands. Only females incubate. Ducklings hatch together within a few hours; after they dry, females lead broods to rearing areas where abundant invertebrates and vegetative cover can be found.
Land-use changes, including drainage in southern Ontario associated with agriculture, deforestation, and urbanization, have altered historical inland and coastal breeding habitats. Winter habitats have been degraded and destroyed by human activities in the Chesapeake Bay and within many mid-Atlantic states. Corresponding with these changes has been a long-term decline in winter populations of American Black Ducks from about 800,000 in the 1950s to 300,000 in the 1990s. The population, which has been the primary source of ducks for hunters in most states and provinces of eastern North America, has been heavily exploited ( Wright 1947 ). A key action that stopped this population decline was a lawsuit brought by the Humane Society of the U.S. et al. ( Humane Society of the United States %AMaine Audubon Society %ASpaulding et al. 1982 ), which led to severe restrictions (30-day season, 1 bird per day limit) on harvest of American Black Ducks in 1983 in the United States and later modest restrictions in Canada. The breeding population increased during the next 15 years.
As an intensively hunted duck of management concern, this species has been well studied, although gaps remain in our knowledge of it. Its breeding ecology has been studied in Maryland ( Stotts and Davis 1960 ), Vermont and Maine ( Coulter and Miller 1968 ), and Quebec ( Reed 1970 ); molting in Labrador ( Bowman 1987b ); and fall staging in Ohio ( Robb 1997 ), Quebec, Nova Scotia, and Vermont (JRL). Controversy regarding the effects of hunting on population declines of this species is described in Blandin 1982 , Grandy 1983 , and Francis et al. 1998a ; possible effects of interactions with the Mallard (Anas platyrhynchos) in Johnsgard 1960c and Ankney et al. 1987 . These issues were also discussed in 2 symposia: Barske 1968 and Kehoe 1997 .