|Anas||rubripes||NA||ne, c, e|
Anas is a genus of dabbling ducks. It includes mallards, wigeons, teals, pintails and shovelers in a number of subgenera. Some authorities prefer to elevate the subgenera to genus rank. Indeed, as the moa-nalos are very close to this clade and may have evolved later than some of these lineages, it is rather the absence of a thorough review than lack of necessity that this genus is rather over-lumped. The phylogeny of this genus is one of the most confounded ones of all living birds. Research is hampered by the fact the radiation of the two major groups of Anas ? the teals and mallard groups ? took place in a very short time and fairly recently, roughly in the mid-late Pleistocene. Furthermore, hybridization may have long played a major role in Anas evolution, with within-subgenus hybrids regularly and between-subgenus hybrids not infrequently being fully fertile. The relationships between species are much obscured by this fact, and mtDNA sequence data is of dubious value in resolving their relationships; on the other hand, nuclear DNA sequences evolve too slowly to resolve the phylogeny of the subgenus Anas for example. Some major clades can be discerned. For example, that the traditional subgenus Anas, the mallard group, forms a monophyletic (in the loose sense, i.e. non-holophyletic) group has never been seriously questioned by modern science and is as good as confirmed (but see below). On the other hand, the phylogeny of the teals is very confusing. For these reasons, the dabbling duck lineages more distantly related to mallard group (which includes the type species of Anas) than the wigeons should arguably be separated in their own genera. These would include the Baikal Teal, the Garganey, the spotted black-capped Punanetta group, and the shovelers and other blue-winged species. Whether the wigeons, which are very distinct in morphology and behavior, but much less so in mtDNA cytochrome b and NADH dehydrogenase subunit 2 sequences, should also be considered a distinct genus Mareca (including the Gadwall and Falcated Duck) is essentially the one remaining point of dispute as regards the question which taxa should remain in this genus and which ones should not.
Sooty brown with a paler head and metallic violet wing patch; feet may be red or brown. Sexes similar except for bills (yellow in male, dull green in female).
Listen to the sound of American Black Duck
[audio:http://www.planetofbirds.com/MASTER/ANSERIFORMES/Anatidae/sounds/American Black Duck.mp3]
Copyright remark: Most sounds derived from xeno-canto
|wingspan min.:||88||cm||wingspan max.:||95||cm|
|size min.:||53||cm||size max.:||61||cm|
|incubation min.:||26||days||incubation max.:||29||days|
|fledging min.:||55||days||fledging max.:||65||days|
Wide variety of aquatic habitats; found on lakes in northern forest and in salt marsh more often than most dabblers. Majority in winter in coastal estuaries and tidal marshes, lesser numbers on inland lakes, tree-lined ponds, wooded swamps.
Nest: Site variable; usually near water, as on banks or small islands, but can be up to a mile distant. Generally on ground among clumps of dense vegetation, sometimes raised as on to
p of stump, in large tree cavity, on duck blind in water. Typical ground nest (built by female) is a shallow depression with plant material added, lined with down.
Clutch 7-11, sometimes 6-12, rarely 4-17. Creamy white to greenish buff. Incubation by female only, 23-33 days, typically 26-29.
Young: All eggs typically hatch in space of a few hours. Female leads young to water, often after dark. Ducklings find their own food. Young fledge at age of about 2 months and are abandoned by female about that time. 1 brood per year.
Diet varies with location and season. On fresh water, feeds mainly on plant material, including seeds, leaves, roots, berries. Seeds of various grasses, pondweeds, sedges, and others often a major part of diet. In tidal zones may feed ma
inly on mussels, clams, snails, small crustaceans, aquatic arthropods. Young ducklings eat many insects.
Behavior: Feeds in water by dabbling, upending, rarely by diving; feeds on land by grazing, plucking seeds, grubbing for roots.
Video American Black Duck
copyright: Robert Schaefer
Those breeding in northern interior may migrate long distances, but coastal and southerly birds may move only short distances. Fall migration is often late in season, as waters freeze or food supply is depleted. Much of migration apparently occurs at nigh