American Black Duck (Anas rubripes)

The American black duck is widely sought by hunters in Eastern Canada. Ironically, however, the greater threat to its survival is that its genes will be gradually eliminated by interbreeding with the mallard duck, which was introduced into its breeding areas as an alternative quarry for hunters.

Description

The American black duck is a dark duck measuring 53-63 cm, about the same size as a mallard. These two species often hybridize, producing offspring with plumage that are intermediate in colouration between their parents. Pure bred black ducks are dark chocolate brown all over, with a lighter brown head and neck, a yellow bill, dark or orange legs and a blue speculum, or wing-patch. Females are smaller than males, and have similar plumage but a darker bill. In flight, this duck shows a white patch under the leading edge of each wing.

Distribution

The American black duck is restricted to freshwater and marine habitats in eastern North America. In Canada, it breeds from eastern Manitoba to the Maritimes and north to the treeline in Labrador. It winters from southeastern Canada south to Florida and Bermuda. Many year-round populations exist, primarily in the southern Great Lakes region.

Ecology

The American black duck is monogamous, and breeds in freshwater and brackish wetlands with abundant emergent vegetation. The nest is concealed in a grass tussock, thicket, or tree stump, usually on or near the ground, but occasionally as high as 14 metres up. The female builds the nest from leaves, grass, and other vegetation, and lines it with down once incubation has begun. Eight to ten creamy or greenish eggs are laid, and are incubated for 26-29 days. The male abandons the female towards the end of the incubation period. The young fledge in 58-63 days.

The American black duck is a dabbling duck; it feeds in shallow water, tipping its body forward so that it can reach the bottom with its bill. While foraging on pond or lake-bottoms, the posterior ends of black ducks are often the only parts of their bodies visible! These ducks feed primarily on aquatic invertebrates, particularly snails, insects, and worms. They also eat berries, the seeds and tubers of aquatic plants, and, in the fall, grain crops. Predators of American black ducks include raccoons, which eat eggs, and also occasionally incubating females. Crows and gulls also steal eggs and ducklings. A further natural threat is flooding, which in years of heavy rainfall may drown eggs.

The American black duck faces several threats, including overhunting, habitat destruction due to agricultural expansion, pesticide poisoning, and competition and interbreeding with the mallard duck.