Information about Anatidae

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Ducks, geese and swans
Black-bellied Whistling Duck (Dendrocygna autumnalis) Black-bellied Whistling Duck (Dendrocygna autumnalis)
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Aves Order: Anseriformes Family: Anatidae Vigors, 1825
Subfamilies
Dendrocygninae Thalassorninae Anserinae Stictonettinae Plectropterinae Tadorninae Anatinae Aythyinae Merginae Oxyurinae and see text

Anatidae is the biological family that includes the ducks and most duck-like waterfowl, such as geese and swans. These are birds that are modified for swimming, floating on the water surface, and in some cases diving in at least shallow water. (The Magpie-goose is no longer considered to be part of the Anatidae, but is placed in its own family Anseranatidae.)

Extant species range in size from the Cotton Pygmy Goose, at as little as 26.5 cm (10.5 inches) and 164 grams (5.8 oz), to the Trumpeter Swan, at as much as 183 cm (6 feet) and 17.2 kg (38 lbs). They have webbed feet and bills which are flattened to a greater or lesser extent. Their feathers are excellent at shedding water due to special oils. Anatidae are remarkable for being one of the few families of birds that possess a penis; they are adapted for copulation on the water only. Duck, eider and goose feathers and down have long been popular for bedspreads, pillows, sleeping bags and coats. The members of this family also have long been used for food.

While the status of the Anatidae as a family is straightforward, and there is little debate about which species properly belong to it, the relationships of the different tribes and subfamilies within it are poorly understood. The listing in the box at right should be regarded simply one of several possible ways of organising the many species within the Anatidae; see discussion in the next section.

Relationship with humans

Humans have had a long relationship with ducks, geese and swans; they are important economically and culturally to humans, and several duck species have benefited from an association with people. On the flip side some anatids are damaging agricultural pests, and have acted as vectors for zoonosis such as avian flu. Numerous ducks and geese have become extinct due to the activities of humans, and many more are currently considered threatened species.

Systematics

The systematics of the Anatinae is currently in a state of flux. Previously divided into six subfamilies, anatomical characters (Livezey 1986) suggest that the Anatidae are better treated in nine subfamilies. This classification has been followed by Madge & Burn (1987). But mtDNA sequence analyses (Sraml et al. 1996, Johnson & Sorenson 1999) indicate that for example the dabbling and diving ducks do not belong into the same subfamily. While there are certainly shortcomings in Livezey's analysis, mtDNA is a bad source for phylogenetic information in many waterfowl (especially dabbling ducks) due to their ability to produce fertile hybrids (Carboneras 1992), in rare cases possibly even beyond the level of genus (see for example the "Barbary Duck"). Due to the small sample size of many molecular studies available to date, mtDNA results must be considered with caution.

But while a comprehensive review of the Anatidae which unites all evidence into a robust phylogeny is still lacking, the reasons for the confusing data are at least clear: As the Late Cretaceous fossil Vegavis iaai - an early modern waterbird which belonged to an extinct family - demonstrates, the Anatidae are an ancient group among the modern birds. Their earliest direct ancestors, though not documented by fossils yet, can likewise be assumed to have been contemporaries with the dinosaurs. The long period of evolution and shifts from one kind of waterbird lifestyle to another have obscured many plesiomorphies, while apomorphies apparently are quite often the result of parallel evolution, for example the "non-diving duck" type displayed by such unrelated genera as Dendrocygna, Amazonetta, and Cairina. For the fossil record, see below.

Alternatively (e.g. Terres & NAS 1991), the Anatidae may be considered to consist of 3 subfamilies (ducks, geese, and swans, essentially) which contain the groups as presented here as tribes, with the swans separated as subfamily Cygninae, the goose subfamily Anserinae also containing the whistling ducks, and the Anatinae containing all other clades.

Dendrocygninae: whistling ducks

One pantropical genus, of distinctive long-legged goose-like birds:

• Dendrocygna: whistling ducks (9 living species)

Thalassorninae: White-backed Duck

One genus in Africa, most closely related to the subfamily Dendrocygninae, though also showing convergent similarities to the subfamily Oxyurinae:

• Thalassornis: White-backed Duck

Anserinae: swans and geese

Three to seven extant genera with 25-30 living species, mainly cool temperate Northern Hemisphere but also some Southern Hemisphere species, with the swans in one genus (two genera in some treatments), and the geese in three genera (two genera in some treatments):

• Cygnus: true swans (7 species, 4 sometimes separated in Olor)
• Anser: grey geese (7 species)
• Chen: white geese (3 species, sometimes included in Anser)
• Branta: black geese (8 living species)

Stictonettinae: Freckled Duck

One genus in Australia, formerly included in the Oxyurinae, but with anatomy suggesting a distinct ancient lineage perhaps closest to the Anserinae, especially the Cape Barren Goose:

• Stictonetta: Freckled Duck

Plectropterinae: Spur-winged Goose

One genus in Africa, formerly included in the "perching ducks", but closer to the Tadorninae:

• Plectropterus: Spur-winged Goose

Tadorninae: shelducks and sheldgeese

This group of larger, often semi-terrestrial waterfowl can be seen as intermediate between Anserinae and Anatinae. Livezey's 1986 revision has resulted in the inclusion of 10 extant genera with about two dozen living species (one probably extinct) in this subfamily, mostly from the Southern Hemisphere but a few in the Northern Hemisphere, but the affiliations of several presumed tadornine genera has later been questioned (Johnson & Sorenson 1999) and the group in the traditional lineup is likely to be paraphyletic:

• Pachyanas: Chatham Island Duck (prehistoric)
• Tadorna: shelducks (7 species, one probably extinct) - possibly paraphletic
• Salvadorina: Salvadori's Teal
• Centrornis: Madagascar Sheldgoose (prehistoric)
• Alopochen: Egyptian Goose and Mascarene Shelducks (1 living species, 2 extinct)
• Neochen: Orinoco Goose
• Chloephaga: sheldgeese (5 species)
• Hymenolaimus: Blue Duck
• Merganetta: Torrent Duck

Anatinae: dabbling ducks and moa-nalos

The dabbling duck group, of worldwide distribution, were previously restricted to just one or two genera, but had been extended by Livezey (1986) to include 8 extant genera and about 55 living species, including several genera formerly known as the "perching ducks"; mtDNA on the other hand confirms that the genus Anas is over-lumped and casts doubt on the diving duck affiliations of several genera (see below):

• Anas: wigeons, gadwalls, teals, pintails, mallards, shovelers, etc (40-50 living species, 3 extinct) - paraphyletic
• Lophonetta: Crested Duck
• Speculanas: Bronze-winged Duck
• Amazonetta: Brazilian Duck

The moa-nalos, of which 4 species in 3 genera are known to date, are a peculiar group of flightless, extinct Anatidae from the Hawaiian Islands. Gigantic in size and with massive bills, they were believed to be geese, but have been shown to be actually very closely related to mallard. They evolved filling the ecological niche of turtles, ungulates and other megaherbivores.

• Chelychelynechen: Turtle-jawed Moa-nalo (prehistoric)
• Thambetochen: Large-billed Moa-nalos (2 species, prehistoric)
• Ptaiochen: Small-billed Moa-nalo (prehistoric)

Aythyinae: diving ducks

Some 15 species of diving ducks, of worldwide distribution, in 2-4 genera; Livezey's 1986 analysis suggests that the probably extinct Pink-headed Duck of India, previously treated separately in Rhodonessa, should be placed in Netta, but this has been questioned (Collar et al. 2001). Furthermore, while morphologically close to dabbling ducks, the mtDNA data indicates that a treatment as distinct subfamily is indeed correct, with the Tadorninae being actually closer to dabbling ducks than the diving ducks are (Johnson & Sorenson, 1999):

• Netta: Red-crested Pochard and allies (4 species, one probably extinct)
• Aythya: pochards, scaups, etc (12 species)

Merginae: eiders, scoters, sawbills and other sea-ducks

There are 9 extant genera and some 20 living species; most of this group occur in the Northern Hemisphere, but two Mergus in the Southern Hemisphere:

• Chendytes: Diving-geese (prehistoric)
• Polysticta: Steller's Eider
• Somateria: eiders (3 species)
• Histrionicus: Harlequin Duck
• Camptorhynchus: Labrador Duck (extinct)
• Melanitta: scoters (3 species)
• Clangula: Long-tailed Duck (1 species)
• Bucephala: goldeneyes (3 species)
• Mergellus: Smew
• Lophodytes: Hooded Merganser
• Mergus: mergansers (5 living species, one extinct).

Oxyurinae: stiff-tail ducks

A small group of 4 genera, 3 of them monotypic, with 8 living species:

• Oxyura: stiff-tailed ducks (5 living species)
• Nomonyx: Masked Duck
• Biziura: Musk Ducks (1 living species)
• Heteronetta: Black-headed Duck

Unresolved

The largest degree of uncertainty concerns whether a number of genera are closer to the shelducks or to the dabbling ducks. See also the monotypic subfamilies above, and the "Perching ducks"

• Coscoroba: Coscoroba Swan - Anserinae or same subfamily as Cereopsis?
• Cereopsis: Cape Barren Goose - Anserinae, Tadorninae, or own subfamily?
• Cnemiornis: New Zealand geese (prehistoric) - as Cereopsis
• Malacorhynchus: Pink-eared ducks (1 living species) - Tadorninae or Oxyurinae?
• Sarkidiornis: Comb Duck - Tadorninae or closer to dabbling ducks?
• Tachyeres: steamer ducks (4 species) - Tadorninae or closer to dabbling ducks?
• Cyanochen: Blue-winged Goose - Tadorninae or more distant clade?
• Nettapus: pygmy geese (3 species) - Anatinae or part of Southern Hemisphere radiation?
• Pteronetta: Hartlaub's Duck - traditionally dabbling ducks, but may be closer to Cyanochen
• Cairina: Muscovy Duck and White-winged Wood Duck (2 species) - traditionally dabbling ducks, but may be paraphyletic, with one species in Tadorninae and the other closer to diving ducks
• Aix: Mandarin Duck and Wood Duck (2 species) - dabbling ducks or Tadorninae?
• Callonetta: Ringed Teal - dabbling ducks or Tadorninae?
• Chenonetta: Maned Duck (1 living species) - dabbling ducks or Tadorninae?
• Marmaronetta: Marbled Duck - Formerly dabbling ducks; actually a diving duck or a distinct subfamily

From subfossil bones found on Kaua‘i (Hawaiian Islands), two enigmatic waterfowl are known. The living and assignable prehistoric avifauna of the archipelago contains as Anseriformes Branta geese and their descendants, and the moa-nalos as mentioned above. The following taxa, although certainly new species, cannot be assigned even to subfamily; that Kaua‘i is the oldest of the large Hawaiian Islands, meaning the species may have been evolving in isolation for nearly up to 10 mya (since the Late Miocene), does not help in determining their affinities:

• Long-legged "Shelduck", Anatidae sp. et gen. indet.
• Small-eyed Duck, Anatidae sp. et gen. indet.

Similarly, Wetmore's Goose (Geochen rhuax) from the Big Island of Hawai‘i, and a gigantic goose-like anatid from O‘ahu are known only from very incomplete and in the former case much damaged bone fragments. The former has been alleged to be a shelduck (Short 1970), but this was generally dismissed because of the damage to the material and biogeographic considerations. The long-legged Kaua‘i bird, however, hints at the possibility of a former tadornine presence on the archipelago, however.

Fossil genera

The fossil record of anatids is extensive, but many prehistoric genera cannot be unequivocally assigned to present-day subfamilies for the reasons given above. Some (such as Eonessa) seem to belong to subfamilies which are completely extinct. For prehistoric species of extant genera, see the respective genus accounts.

• Paracygnus (Kimball Late Pliocene of Nebraska, USA) - anserine
• Eremochen (Pliocene) - anserine
• Cygnavus (Early Oligocene of Kazakhstan - Early Miocene of Germany) - anserine
• Presbychen (Temblor Late Miocene of Sharktooth Hill, USA) - anserine
• Anabernicula (Late Pliocene ?- Late Pleistocene of SW and W North America) - tadornine
• Brantadorna (Middle Pleistocene of Vallecito Creek, USA) - tadornine
• Nannonetta (Late Pleistocene of Peru) - tadornine?
• Eonessa (Eocene of Utah, USA)
• Romainvillia (Early Oligocene of Belgium ?- Late Eocene of France)
• Cygnopterus (Middle Oligocene of Belgium - Early Miocene of France)
• Guguschia (Oligocene of Azerbaijan)
• Mionetta (Late Oligocene - Middle Miocene of C Europe)
• Megalodytes (Middle Miocene of California, USA)
• "cf. Megalodytes" (Haraichi Middle Miocene of Annaka, Japan)
• Anatidae gen. et sp. indet. (Sajóvölgyi Middle Miocene of Mátraszõlõs, Hungary: Gál et al. 1998-99)
• Afrocygnus (Late Miocene ?- Early Pliocene of C Sahara, Africa)
• Balcanas (Early Pliocene of Dorkovo, Bulgaria) - tadornine? May be synonym of Tadorna or even Common Shelduck
• "Chenopis" nanus - at least 2 taxa (Pleistocene of Australia)
• Aldabranas (Pleistocene of Aldabra, Indian Ocean)
• Dendrochen
• Sinanas
• Wasonaka

Putative or disputed prehistoric anatids are:

• Loxornis (Deseado Early Oligocene of Argentina)
• Paracygnopterus (Early Oligocene of Belgium and England)
• Limicorallus (Indricotherium Middle Oligocene of Chelkar-Teniz, Kazakhstan)
• Teleornis (Deseado Early Oligocene of Argentina)
• Paranyroca (Rosebud Early Miocene of Bennett County, USA)
• Eoneornis (Miocene of Argentina) - a nomen dubium
• Eutelornis (Miocene of Argentina)

References

• Carboneras, Carles (1992): Family Anatidae (Ducks, Geese and Swans). In: del Hoyo, Josep; Elliott, Andrew & Sargatal, Jordi (editors): Handbook of Birds of the World, Volume 1: Ostrich to Ducks: 536-629. Lynx Edicions, Barcelona. ISBN 84-87334-10-5
• Collar, N. J.; Andreev, A. V.; Chan, S.; Crosby, M. J.; Subramanya, S. & Tobias, J. A. (editors) (2001): Pink-headed Duck. In:Threatened Birds of Asia: The BirdLife International Red Data Book, p.489-501. BirdLife International. ISBN 0-946888-44-2 HTML fulltext
• Gál, Erika; Hír, János; Kessler, Eugén & Kókay, József (1998-99): Középsõ-miocén õsmaradványok, a Mátraszõlõs, Rákóczi-kápolna alatti útbevágásból. I. A Mátraszõlõs 1. lelõhely [Middle Miocene fossils from the sections at the Rákóczi chapel at Mátraszőlős. Locality Mátraszõlõs I.]. Folia Historico Naturalia Musei Matraensis 23: 33-78. [Hungarian with English abstract] PDF fulltext
• Johnson, Kevin P. & Sorenson, Michael D. (1999): Phylogeny and biogeography of dabbling ducks (genus Anas): a comparison of molecular and morphological evidence. Auk 116(3): 792–805. PDF fulltext
• Livezey, Bradley C. (1986): A phylogenetic analysis of recent anseriform genera using morphological characters. Auk 103(4): 737-754. PDF fulltext
• Madge, Steve & Burn, Hilary (1987): Wildfowl : an identification guide to the ducks, geese and swans of the world. Christopher Helm, London. ISBN 0-7470-2201-1
• Short, Lester L. (1970): A new anseriform genus and species from the Nebraska Pliocene. Auk 87(3): 537-543. PDF fulltext
• 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 (HTML abstract)
• Terres, John K. & National Audubon Society (1991): The Audubon Society Encyclopedia of North American Birds. Wings Books, New York. ISBN 0-517-03288-0

External links

• Anatidae videos on the Internet Bird Collection
• Anatidae sounds on the xeno-canto collection