The redhead (Aythya americana) is a medium-sized diving duck. The 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 long with an wingspan. Redhead weight ranges from 2.0 to 2.5 lbs (907-1134 g), with males weighing an average of 2.4 lbs (1089 g) and females weighing an average of 2.1 lbs (953 g). It belongs to the genus Aythya, together with 11 other described species. The redhead and the common pochard form a sister group which together is sister to the canvasback. The redhead goes by many names, including the red-headed duck and the red-headed pochard. This waterfowl is easily distinguished from other ducks by the male's copper coloured head and bright blue bill during the breeding season. Taxonomy and phylogeny Taxonomy The redhead is in the family Anatidae (ducks, swans, geese) and genus Aythya (diving ducks). There are currently no described subspecies of the redhead. The two syntype specimens of Fuligula americana Eyton (Monogr. Anat., 1838, p.155) 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). The specimens were collected in North America and came to the Liverpool national collection via Thomas Campbell Eyton’s collection and the 13th Earl of Derby’s collection which was bequeathed to the city of Liverpool. Phylogeny The redhead and the common pochard form a sister group which itself is sister to the canvasback. This group is then sister to the monophyletic group consisting of the white-eyes (hardhead, Madagascar pochard, and the sister species ferruginous duck and baer's pochard) and scaups (New Zealand scaup, ring-necked duck, tufted duck, greater scaup, lesser scaup). Description The redhead is a pochard, a diving duck specially adapted to foraging underwater. Their legs are placed farther back on the body, which makes walking on land difficult, the webbing on their feet is larger than dabbling ducks and their bills are broader, to facilitate underwater foraging. In addition, pochards have a lobed hind toe. No pochard has a metallic coloured speculum, something that is characteristic of other ducks. Males During breeding season, adult males have a copper head and neck, with a black breast. The back and sides are grey, the belly is white and the rump and tail are a light black. Male bills are pale blue