Kingdom [Animalia] Linnaeus, 1758 - animals
   Subkingdom Metazoa Haeckel, 1874 see Kingdom Animalia Linnaeus, 1758
     Division Eumetazoa Butschli, 1910 see Subkingdom Eumetazoa Butschli, 1910
       Subdivision Bilateralia
         Phylum Chordata Bateson, 1885 - chordates
           Subphylum Vertebrata Cuvier, 1812 - vertebrates
             Class Aves Linnaeus, 1758 - birds see Subclass Aves Linnaeus, 1758
               Subclass Neornithes Gadow, 1893 see Clade Neornithes Gadow, 1893
                 Order Anseriformes Wagler, 1831 - waterfowl and screamers
                   Family Anatidae Vigors, 1825 - ducks, geese, swans
                     Subfamily Anatinae Vigors, 1825 - pond ducks
                       Tribe Aythyini see Subfamily Anatinae Vigors, 1825
                         Genus Aythya Boie, 1822 - hardhead
                           01 Aythya ferina (Linnaeus, 1758) - common pochard
                           02 Aythya valisneria (Wilson, 1814) see Aythya valisineria (Wilson, 1814)
                           03 Aythya americana (Eyton, 1838) - redhead
                           04 Aythya nyroca (Güldenstädt, 1770) - ferruginous duck
                           05 Aythya innotata (Salvadori, 1894) - Madagascan pochard
                           06 Aythya australis (Eyton, 1838) - hardhead
                           07 Aythya baeri (Radde, 1863) - Baer's pochard
                           08 Aythya fuligula (Linnaeus, 1758) - tufted duck
                           09 Aythya collaris (Donovan, 1809) - ring-necked duck
                           10 Aythya novaeseelandiae (Gmelin, 1789) - New Zealand scaup
                           11 Aythya marila (Linnaeus, 1761) - greater scaup
                           12 Aythya affinis (Eyton, 1838) - lesser scaup