The perching ducks were previously treated as a small group of ducks in the duck

Duck

Duck is the common name for a large number of species in the Anatidae family of birds, which also includes swans and geese. The ducks are divided among several subfamilies in the Anatidae family; they do not represent a monophyletic group but a form taxon, since swans and geese are not considered...

, goose

Goose

The word goose is the English name for a group of waterfowl, belonging to the family Anatidae. This family also includes swans, most of which are larger than true geese, and ducks, which are smaller....

 and swan

Swan

Swans, genus Cygnus, are birds of the family Anatidae, which also includes geese and ducks. Swans are grouped with the closely related geese in the subfamily Anserinae where they form the tribe Cygnini. Sometimes, they are considered a distinct subfamily, Cygninae...

 family Anatidae

Anatidae

Anatidae is the biological family of birds that includes ducks, geese and swans. The family has a cosmopolitan distribution, occurring on all the world's continents except Antarctica and on most of the world's islands and island groups...

, grouped together on the basis of their readiness to perch high in tree

Tree

A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

s. It has been subsequently shown that the grouping is paraphyletic and their apparent similarity results from convergent evolution

Convergent evolution

Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...

, with the different members more closely related to various other ducks than to each other (Livezey 1986).

The species previously included, and their current subfamilial allocation, are:

Plectropterinae

• Spur-winged Goose
  Spur-winged Goose
  The Spur-winged Goose is a large bird in the family Anatidae, related to the geese and the shelducks, but distinct from both of these in a number of anatomical features, and therefore treated in its own subfamily, the Plectropterinae...
  
   Plectropterus gambensis

Tadorninae

Tadorninae

The Tadorninae is the shelduck-sheldgoose subfamily of the Anatidae, the biological family that includes the ducks and most duck-like waterfowl such as the geese and swans....

• Salvadori's Teal
  Salvadori's Teal
  The Salvadori's Teal or Salvadori's Duck is a species of bird native to New Guinea. It is placed in the monotypic genus Salvadorina....
  
   Salvadorina waigiuensis (initially placed in Anatinae)
• Blue Duck
  Blue Duck
  The Blue Duck is a member of the duck, goose and swan family Anatidae endemic to New Zealand. It is the only member of the genus Hymenolaimus, placed in the shelduck subfamily Tadorninae after previously being considered part of the paraphyletic "perching duck" assemblage...
  
   Hymenolaimus malacorhynchos
• Torrent Duck
  Torrent Duck
  The Torrent Duck is a member of the duck, goose and swan family Anatidae. It is the only member of the genus Merganetta. Today it is placed in the shelduck subfamily Tadorninae after the "perching duck" assemblage where it was formerly assigned to was dissolved because it turned out to be...
  
   Merganetta armata

Anatinae

Anatinae

The Anatinae is a subfamily of the family Anatidae . Its surviving members are the dabbling ducks, which feed mainly at the surface rather than by diving...

• Brazilian Teal Amazonetta brasiliensis

In addition, several species cannot with certainty be allocated to a subfamily, though they do not form a distinct clade

Clade

A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

. Rather, their characters are too ambiguous to allow unequivocal placement based on the available data (Livezey 1986, Sraml et al. 1996, Johnson & Sorenson 1999):

• Comb Duck
  Comb Duck
  The Knob-billed Duck , or Comb Duck, is an unusual, pan-tropical duck, found in tropical wetlands in sub-Saharan Africa, Madagascar and south Asia from Pakistan to Laos and extreme southern China...
  
   Sarkidiornis melanotos: Tadorninae or basal
  Basal (phylogenetics)
  In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
  
   Anatinae?
• Pink-eared Duck
  Pink-eared Duck
  The Pink-eared Duck is a species of duck found in Australia.It has a large spatulate bill like the Australasian Shoveler, but is smaller at 38–40 cm length. Its brown back and crown, black and white barred sides and black eye patches on its otherwise white face make this bird unmistakable...
  
   Malacorhynchus membranaceus: Tadorninae or Oxyurinae
  Oxyurinae
  Oxyurinae is a subfamily of the duck, goose and swan family of birds, Anatidae. It has been subject of considerable debate about its validity and circumscription. Most of its members have long stiff tail feathers which are erected when the bird is at rest, and relatively large swollen bills...
  
  ?
• Hartlaub's Duck
  Hartlaub's Duck
  The Hartlaub's Duck is a dark chestnut-coloured duck of African forests. Formerly included in the paraphyletic "perching duck" assemblage, it was later moved to the dabbling duck assemblage...
  
   Pteronetta hartlaubi: Anatinae or a very distinct clade?
• Green Pygmy Goose
  Green Pygmy Goose
  The Green Pygmy Goose is a small perching duck which breeds in southern New Guinea and northern Australia.First described in 1842 by the ornithologist John Gould, its specific name is derived from diminutive of the Latin adjective pulcher "pretty". It is one of three species in the Afro-Asian...
  
   Nettapus pulchellus: Anatinae or a Gondwana
  Gondwana
  In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
  
  n clade?
• Cotton Pygmy Goose
  Cotton Pygmy Goose
  The Cotton Pygmy Goose or the Cotton Teal, Nettapus coromandelianus is a small perching duck which breeds in Pakistan, India, Bangladesh, southeast Asia and south to northern Australia.-Description:...
  
   Nettapus coromandellanus: Anatinae or a Gondwanan clade?
• African Pygmy Goose
  African Pygmy Goose
  The African Pygmy Goose is a very small perching duck from sub-Saharan Africa. It has been featured in many Vietnamese pornographic films. It is the smallest African waterfowl. It is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds applies....
  
   Nettapus auritus: Anatinae or a Gondwanan clade?
• Muscovy Duck
  Muscovy Duck
  The Muscovy Duck is a large duck which is native to Mexico and Central and South America. A small wild population reaches into the United States in the lower Rio Grande Valley of Texas...
  
   Cairina moschata: Anatinae or Tadorninae?
• White-winged Duck Cairina scutulata: Anatinae or closer to Aythyinae?
• Wood Duck
  Wood Duck
  The Wood Duck or Carolina Duck is a species of duck found in North America. It is one of the most colourful of North American waterfowl.-Description:...
  
   Aix sponsa: Anatinae or Tadorninae?
• Mandarin Duck
  Mandarin Duck
  The Mandarin Duck , or just Mandarin, is a medium-sized perching duck, closely related to the North American Wood Duck. It is 41–49 cm long with a 65–75 cm wingspan.-Description:...
  
   Aix galericulata: Anatinae or Tadorninae?
• Ringed Teal
  Ringed Teal
  The Ringed Teal is a small duck of South American forests. It is the only species of the genus Callonetta...
  
   Callonetta leucophrys: Anatinae or Tadorninae?
• Maned Duck Chenonetta jubata: Anatinae or Tadorninae?