Class Aves Linnaeus, 1758 - birds see Subclass Aves Linnaeus, 1758
   Subclass Neornithes Gadow, 1893 see Clade Neornithes Gadow, 1893
     Infraclass Neoaves Sibley et al., 1988 see Subcohort Neoaves Sibley et al., 1988
       Parvclass Galloanserae Sibley, Ahlquist & Monroe Jr., 1988 see Subcohort Galloanserae Sibley, Ahlquist & Monroe Jr., 1988
         Superorder Anserimorphae see Order Anseriformes Wagler, 1831
           Order Anseriformes Wagler, 1831 - waterfowl and screamers
             Infraorder Anserides see Suborder Anseres Linnaeus, 1758
               Family Anatidae Vigors, 1825 - ducks, geese, swans
                 Subfamily Anatinae Vigors, 1825 - pond ducks
                   Tribe Anatini Vigors, 1825 - typical ducks see Subfamily Anatinae Vigors, 1825
                     Genus Aythya Boie, 1822 - hardhead
                       01 Aythya ferina (Linnaeus, 1758) - common pochard
                       02 Aythya valisineria (Wilson, 1814) - canvasback
                       03 Aythya americana (Eyton, 1838) - redhead
                       04 Aythya collaris (Donovan, 1809) - ring-necked duck
                       05 Aythya nyroca (Güldenstädt, 1770) - ferruginous duck
                       06 Aythya innotata (Salvadori, 1894) - Madagascan pochard
                       07 Aythya baeri (Radde, 1863) - Baer's pochard
                       08 Aythya australis (Eyton, 1838) - hardhead
                       09 Aythya fuligula (Linnaeus, 1758) - tufted duck
                       10 Aythya novaeseelandiae (Gmelin, 1789) - New Zealand scaup
                       11 Aythya marila (Linnaeus, 1761) - greater scaup
                       12 Aythya affinis (Eyton, 1838) - lesser scaup