美洲潜鸭种

The redhead (Aythya americana) is a medium-sized diving duck. Its scientific name is derived from Greek aithuia, an unidentified seabird mentioned by authors including Hesychius and Aristotle, and Latin americana, of America. The redhead is 40–56 cm (16–22 in) long with an 74–84 cm (29–33 in) wingspan; weights range from 1,030–1,080 g (36–38 oz), with males weighing an average of 1,080 g (38 oz) and females an average of 1,030 g (36 oz). It belongs to the genus Aythya, together with 11 other described species. The redhead and the common pochard form a sister group, which together are sister to the canvasback. This waterfowl is easily distinguished from most other ducks by the male's copper-colored head and pale blue bill during the breeding season; from its close relative, canvasback, it is distinguished by the more rounded head, shorter bill, and (in the males) yellow, not red, eyes. The Eurasian common pochard is even more similar, but very rarely overlaps in range; it also differs in having a red eye, and a more acute, less rounded head shape.

Other names that have been used for the redhead include red-headed duck and the red-headed pochard.

Taxonomy and phylogeny

Taxonomy

The redhead is in the family Anatidae (ducks, swans, geese) and genus Aythya (diving ducks). Currently, no subspecies of the redhead are accepted.

The two syntype specimens of Fuligula americana Eyton are held in the vertebrate zoology collections of National Museums Liverpool at World Museum, with accession numbers NML-VZ D829 (male immature) and NML-VZ D829a (female adult).

Description

The redhead is a pochard, a diving duck specially adapted to foraging underwater. Its legs are placed further back on the body, which makes walking on land difficult. The webbing on its feet is larger than dabbling ducks and its bills are broader to facilitate underwater foraging. In addition, pochards have a lobed hind toe. No pochard has a metallic-colored speculum, a characteristic of other ducks.

Distribution

During breeding season, redheads are found across a wide range of North America, from as far north as Northern Canada, south to the Caribbean in winter. Their preferred areas include the intermontane regions of British Columbia, Alberta, Saskatchewan, Manitoba, with some small localities in Ontario and Quebec, and North and South Dakota inn the United States. These pochards then migrate south to winter in warmer climates.

Habitat

Small, semipermanent wetlands in nonforested country where the water is deep enough to provide dense emergent vegetation is considered ideal breeding habitat for redheads. When wintering, redheads switch to large areas of water near the coast that are protected from wave action, but can also be found in reservoirs, lakes, playa wetlands, freshwater river deltas, coastal marshes, estuaries, and bays.

Predators

Redheads do not have many predators and are most likely to die of disease or indirect human impact. These ducks are considered less desirable as table fare than other puddle ducks like the mallard. However, their beautiful plumage makes them a targeted species for waterfowl hunters looking to focus on diving ducks. Adults can be preyed upon by northern river otters, red-tailed hawks, great horned owls, bald eagles, golden eagles, and to a greater extent, minks.

Population status

The North American Waterfowl Management Plan for redheads is 760,000 North American birds. The population size has increased in the past few decades to well over 1.4 million birds. Redheads make up 2% of North America's duck population and only 1% of its harvested ducks. Populations may be stable because of restrictive bag limits for the species. In addition, the species uses semipermanent and permanent wetlands to breed, and these habitats are less likely to be affected by drought.

Behavior

Migration

Spring

Redheads begin to leave their winter range in late January and February with the northernmost birds migrating by late April. In western North America, migrants begin arriving in Oregon, British Columbia, and Colorado in February. In central North America, migrants arrive as soon as temperatures open wetlands and lakes, which can range from late February (Nebraska) to early May (Alberta, Manitoba, and Iowa).