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American Black Duck

 

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Common Name: American Black Duck

Scientific Name: Anas rubripes

Nest Type: Scrape

Nest Location: Ground, tree or stump

Clutch Size: 6-12; avg. 8-10

Food: Aquatic invertebrates, seeds, and tubers

Foraging Guild: Dabbler

The American Black Duck is a regular breeding species throughout northeastern Minnesota and an uncommon winter visitor in southeastern parts of the state, particularly at Silver Lake and Black Dog Lake (Janssen 1987). Peak spring migration typically occurs in mid-April, and the bulk of fall migration takes place throughout October (Janssen 1987). Minnesota is on the southwestern edge of the Black Duck's breeding range, which extends north to the shores of Hudson's Bay and east to the Atlantic Coast from North Carolina to the southern edge of the tundra. Wintering birds may migrate to the southern Great Lakes States, or as far south as northern Georgia, Alabama, Louisiana and northeastern Texas (National Geographic Society 1983).

Breeding habitat of the American Black Duck includes a wide variety of riparian forest types, wetlands, and water types free of human disturbance. Fall and winter habitat preferences are similarly broad, including most types of unfrozen water. Larger bodies of water are preferred, however (Spencer 1986). In Minnesota, this species requires wetland habitat which contains adequate emergent vegetation and aquatic invertebrates.

American Black Ducks are considered "dabblers," feeding primarily in shallow fresh and brackish water on invertebrates, small amphibians, seeds and other plant material (Roberts 1932, Spencer 1986). Nestlings and breeding females rely more heavily on aquatic invertebrates than many other dabbling duck species to provide needed protein. Upland feeding sites are used occasionally (Spencer 1986).

Nests are built on the ground, and are typically depressions lined with dry plant material and down. They are usually well hidden near small beaver ponds in grassy areas, wooded wetlands, or the riparian zone of boreal forest (Ehrlich et al. 1988, Cadman et al. 1987). Most nests are within 75 m of water (Spencer 1986). Abandoned nests of raptors and large corvids are occasionally used (Roberts 1932). Nesting in Minnesota occurs from mid-May through late July (Roberts 1932). Eight to ten eggs are usually laid and incubated by the female for 23 to 33 days prior to hatching. The precocial young are ready to fledge 58 to 60 days after hatching (Spencer 1986). Nest predation by American Crow, Herring Gull, Great Black-backed Gull and Red fox have been reported in Ontario (Atlantic Waterfowl Council 1968).

Population declines throughout the U.S. have been linked not only to habitat changes but also to lead poisoning, pesticide use for controlling spruce budworm, acid rain, overhunting (a disproportionately large harvest of young female black ducks may be accelerating population declines), and competition and hybridization with Mallards (Spencer 1986). Habitat alteration may be causing population decreases indirectly by facilitating the range expansion of Mallards which prefer less forested habitats (Cadman et al. 1987). Concern over Black Duck population declines began as early as the middle of this century (Spencer 1986). One nationwide survey indicates a 2% per year decline for the period 1955 to 1983, with present populations estimated at 40% of those at the beginning of the period (Grandy 1983). These population declines have led to listing the species on the Audubon Blue List (1980-1981), and identifying it as a Species of Special Concern in 1982 and 1986 (Ehrlich et al. 1988). In Minnesota, the species has increased by about 2% in the past 25 years (Janssen 1990). However, the sampling efficiency for this species is quite low and it was only observed on 4 routes.