The perching ducks ("Cairininae" or "Cairinini") were previously treated as a small group of ducks in the duck, goose and swan family Anatidae, grouped together on the basis of their readiness to perch high in trees. It has been subsequently shown that the grouping is paraphyletic and their apparent similarity results from convergent evolution, with the different members more closely related to various other ducks than to each other.
The species previously included, and their current subfamilial allocation, are:
Plectropterinae
Spur-winged goose Plectropterus gambensis
Tadorninae
Salvadori's teal Salvadorina waigiuensis (initially placed in Anatinae)
Blue duck Hymenolaimus malacorhynchos
Torrent duck Merganetta armata
Anatinae
Brazilian teal Amazonetta brasiliensis
In addition, several species cannot with certainty be allocated to a subfamily, though they do not form a distinct clade. Rather, their characters are too ambiguous to allow unequivocal placement based on the available data:
Comb duck Sarkidiornis melanotos: Tadorninae or basal Anatinae?
Pink-eared duck Malacorhynchus membranaceus: Tadorninae or Oxyurinae?
Hartlaub's duck Pteronetta hartlaubi: Anatinae or a very distinct clade?
Green pygmy goose Nettapus pulchellus: Anatinae or a Gondwanan clade?
Cotton pygmy goose Nettapus coromandellanus: Anatinae or a Gondwanan clade?
African pygmy goose Nettapus auritus: Anatinae or a Gondwanan clade?
Muscovy duck Cairina moschata: Anatinae or Tadorninae?
White-winged duck Cairina scutulata: Anatinae or closer to Aythyinae?
Wood duck Aix sponsa: Anatinae or Tadorninae?
Mandarin duck Aix galericulata: Anatinae or Tadorninae?
Ringed teal Callonetta leucophrys: Anatinae or Tadorninae?
Maned duck Chenonetta jubata: Anatinae or Tadorninae?
