|Common shelduck (Tadorna tadorna)|
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This group is largely tropical or Southern Hemisphere in distribution, with only two species, the common shelduck and the ruddy shelduck breeding in northern temperate regions, though the crested shelduck (presumed extinct) was also a northern species.
Most of these species have a distinctive plumage, but there is no pattern as to whether the sexes are alike, even within a single genus.
Following the review of Livezey (1986), several species formerly classified as aberrant dabbling ducks or as "perching ducks" were placed in the Tadorninae. mtDNA sequence analyses cast doubt on the allocation of several genera; many supposed dabbling ducks and one peculiar goose may more correctly belong here, while some genera believed to be close to shelducks appear to have different relationships altogether.
The available data indicates that the Tadorninae are indeed, as their appearance suggests, somewhat intermediate between geese and dabbling ducks, but the molecular data suggests they are not the only lineage to evolve towards a more duck-like morphology, with the diving ducks and seaducks being more distant.
- Unequivocally placed in this group:
- Tadorna: shelducks (Europe, Africa, Australasia; 7 species) – possibly paraphyletic
- Salvadorina: Salvadori's teal (New Guinea)—formerly in Anatidae and "perching ducks"
- Centrornis: Madagascar sheldgoose (Madagascar, prehistoric)
- Alopochen: African and Mascarene shelducks (Africa and Madagascar region; 1 living species, 2–3 extinct)
- Neochen: Orinoco goose and Andean goose (South America)
- Chloephaga: sheldgeese (South America; 4 species)
- Hymenolaimus: blue duck (New Zealand)—formerly in "perching ducks"
- Merganetta: torrent duck (Andes mountains, South America) – formerly in "perching ducks"
- Provisionally placed in this group:
- Malacorhynchus: pink-eared ducks (Australia; 1 living species, 1 prehistoric) – may be closer to Oxyurinae
- Sarkidiornis: comb duck (South America, Africa, India) – formerly in "perching ducks"; may belong to Anatinae
- Cyanochen: blue-winged goose (Ethiopia) – may belong to a distinct subfamily
- Tachyeres: steamer ducks (South America; 4 species) – may belong to Anatinae
- May belong to Tadorninae, currently placed elsewhere:
- Aix: Mandarin duck and wood duck (East Asia and North America, respectively)
- Cairina moschata: Muscovy duck (tropical America; genus Cairina may be paraphyletic)
- Cereopsis: Cape Barren goose (Australia)
- Callonetta: ringed teal (South America)
- Chenonetta: maned duck (Australia and formerly New Zealand; 1 living species, 1 extinct)
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- Livezey, Bradley C. (1986). "A phylogenetic analysis of recent anseriform genera using morphological characters" (PDF). Auk. 103 (4): 737–754.
- Sraml, M.; Christidis, L.; Easteal, S.; Horn, P. & Collet, C. (1996). "Molecular Relationships Within Australasian Waterfowl (Anseriformes)". Australian Journal of Zoology. 44 (1): 47–58. doi:10.1071/ZO9960047.
- Johnson, Kevin P. & Sorenson, Michael D. (1999). "Phylogeny and biogeography of dabbling ducks (genus Anas): a comparison of molecular and morphological evidence" (PDF). Auk. 116 (3): 792–805. doi:10.2307/4089339.