TheAnatidae are the biologicalfamily ofwater birds that includesducks,geese, andswans. The family has acosmopolitan distribution, occurring on all the world's continents except Antarctica. Thesebirds are adapted forswimming, floating on the water surface, and, in some cases, diving in at least shallow water. The family contains around 174 species in 43genera (themagpie goose is no longer considered to be part of the Anatidae and is now placed in its own family,Anseranatidae).
They are generally herbivorous and aremonogamous breeders. A number of species undertakeannual migrations. A few species have been domesticated for agriculture, and many others are hunted for food and recreation. Five species have become extinct since 1600, and many more arethreatened withextinction.
The ducks, geese, and swans are small- to large-sized birds with a broad and elongated general body plan.[2] Diving species vary from this in being rounder. Extant species range in size from thecotton pygmy goose, at as little as 26.5 cm (10.5 in) and 164 g (5.8 oz), to thetrumpeter swan, at as much as 183 cm (6 ft) and 17.2 kg (38 lb). The largest anatid ever known is the extinct flightlessGarganornis ballmanni at 22 kg (49 lb). The wings are short and pointed, and supported by strong wing muscles that generate rapid beats inflight. They typically have long necks, although this varies in degree between species. The legs are short, strong, and set far to the back of the body (more so in the more aquatic species), and have a leathery feel with a scaly texture. Combined with their body shape, this can make some species awkward on land, but they are stronger walkers than other marine and water birds such asgrebes orpetrels. They typically havewebbed feet, though a few species such as theNene have secondarily lost their webbing. The bills are made of soft keratin with a thin and sensitive layer of skin on top (which has a leathery feel when touched). For most species, the shape of the bill tends to be more flattened to a greater or lesser extent. These contain serratedlamellae which are particularly well defined in the filter-feeding species.[2]
Their feathers are excellent at shedding water due to special oils. Many of the ducks displaysexual dimorphism, with the males being more brightly coloured than the females (although the situation is reversed in species such as theparadise shelduck). The swans, geese, and whistling-ducks lack sexually dimorphic plumage. Anatids are vocal birds, producing a range of quacks, honks, squeaks, and trumpeting sounds, depending on species; the female often has a deeper voice than the male.[3]
Anatids are generallyherbivorous as adults, feeding on various water-plants, although some species also eat fish, molluscs, or aquatic arthropods. One group, themergansers, are primarilypiscivorous, and have serrated bills to help them catch fish. In a number of species, the young include a high proportion of invertebrates in their diets, but become purely herbivorous as adults.[3]
The anatids are generally seasonal andmonogamous breeders. The level of monogamy varies within the family; many of the smaller ducks only maintain the bond for a single season and find a new partner the following year, whereas the larger swans, geese and some of the more territorial ducks maintain pair bonds over a number of years, and even for life in some species. However, forcedextrapair copulation among anatids is common, occurring in 55 species in 17 genera.[4]
Anatidae is a large proportion of the 3% of bird species to possess apenis,[5][6] though they vary significantly in size, shape, and surface elaboration.[7] Most species are adapted forcopulation on the water only. They construct simple nests from whatever material is close at hand, often lining them with a layer of down plucked from the mother's breast. In most species, only the femaleincubates the eggs. The young areprecocial, and are able to feed themselves from birth.[3] One aberrant species, theblack-headed duck, is an obligatebrood parasite, laying its eggs in the nests ofgulls andcoots. While this species never raises its own young, a number of other ducks occasionally lay eggs in the nests of conspecifics (members of the same species) in addition to raising their own broods.
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.
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. However, some anatids areagriculturalpests, and have acted as vectors forzoonoses such asavian influenza.
Since 1600, five species of ducks have becomeextinct due to the activities of humans,[citation needed] and subfossil remains have shown that humans caused numerous extinctions in prehistory. Today, many more are consideredthreatened. Most of the historic and prehistoric extinctions were insular species, vulnerable due to small populations (oftenendemic to a single island), andisland tameness. Evolving on islands that lacked predators, these species lost antipredator behaviours, as well as the ability to fly, and were vulnerable to human hunting pressure andintroduced species. Other extinctions and declines are attributable to overhunting,habitat loss and modification, and hybridisation with introduced ducks (for example the introducedruddy duck swamping thewhite-headed duck in Europe). Numerous governments and conservation and hunting organisations have made considerable progress in protecting ducks and duck populations through habitat protection and creation, laws and protection, and captive-breeding programmes.
The name Anatidae for thefamily was introduced by the English zoologistWilliam Elford Leach in a guide to the contents of theBritish Museum published in 1819.[8][9] While the status of the Anatidae as a family is straightforward, and which species properly belong to it is little debated, the relationships of the different tribes and subfamilies within it are poorly understood. The listing in the box at right should be regarded as simply one of several possible ways of organising the many species within the Anatidae; see discussion in the next section.
The systematics of the Anatidae are in a state of flux. Previously divided into six subfamilies,[citation needed] a study of anatomical characters by Livezey[10] suggests the Anatidae are better treated in nine subfamilies. This classification was popular in the late 1980s to 1990s.[11] ButmtDNAsequence analyses[12][13] indicate, for example, the dabbling and diving ducks do not belong in the same subfamily.
While shortcomings certainly occur in Livezey's analysis,[citation needed] mtDNA is an unreliable source for phylogenetic information in many waterfowl (especially dabbling ducks) due to their ability to produce fertilehybrids,[2] in rare cases possibly even beyond the level of genus (see for example the "Barbary duck"). Because thesample size of many molecular studies available to date is small, mtDNA results must be considered with caution.
While a comprehensive review of the Anatidae which unites all evidence into a robustphylogeny is still lacking, the reasons for the confusing data are at least clear: As demonstrated by theLate CretaceousfossilVegavis iaai—an early modern waterbird which belonged to an extinct lineage—the Anatidae are an ancient group among the modern birds. Their earliest direct ancestors, though not documented by fossils yet, likewise can be assumed[citation needed] to have been contemporaries with the non-aviandinosaurs. The long period ofevolution and shifts from one kind of waterbird lifestyle to another have obscured manyplesiomorphies, while apparentapomorphies are quite often the result ofparallel evolution, for example the "non-diving duck" type displayed by such unrelated genera asDendrocygna,Amazonetta, andCairina. For the fossil record, see below.
Alternatively,[14] the Anatidae may be considered to consist of three subfamilies (ducks, geese, and swans, essentially) which contain the groups as presented here astribes, with the swans separated as subfamilyCygninae, the goose subfamily Anserinae also containing the whistling ducks, and the Anatinae containing all otherclades.
Subfamily:Anserinae, swans and geese (3–7 extant genera with 25–30 living species, mainly cool temperate Northern Hemisphere, but also some Southern Hemisphere species, with theswans in one genus [two genera in some treatments], and thegeese in three genera [two genera in some treatments]. Some other species are sometimes placed herein, but seem somewhat more distinct [seebelow])
Cygnus, true swans (6 species, 4 sometimes separated inOlor)
Subfamily: Stictonettinae (one genus in Australia, formerly included in the Oxyurinae, but with anatomy suggesting a distinct ancient lineage perhaps closest to the Anserinae, especially theCape Barren goose)
Subfamily:Tadorninae – shelducks and sheldgeeseMalecommon shelduck (This group of larger, often semiterrestrial waterfowl can be seen as intermediate between Anserinae and Anatinae. The 1986 revision[10] 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; the affiliations of several presumed tadornine genera has later been questioned[13] and the group in the traditional lineup is likely to beparaphyletic.)
Subfamily:Aythyinae, diving ducks (Some 15 species ofdiving ducks, of worldwide distribution, in two to four genera; The 1986 morphological analysis[10] suggested the probably extinctpink-headed duck of India, previously treated separately inRhodonessa, should be placed inNetta, but this has been questioned.[15] Furthermore, while morphologically close to dabbling ducks, the mtDNA data indicate a treatment as distinct subfamily is indeed correct, with the Tadorninae being actually closer to dabbling ducks than the diving ducks[13])
Netta, red-crested pochard and allies (4 species, 1 probablyextinct)
Subfamily:Anatinae, dabbling ducks and moa-nalos (Thedabbling duck group, of worldwide distribution, were previously restricted to just one or two genera, but had been extended[10] to include eight extant genera and about 55 living species, including several genera formerly known as the "perching ducks"; mtDNA on the other hand confirms that the genusAnas is over-lumped and casts doubt on the diving duck affiliations of several genera [see below]. Themoa-nalos, of which four species in three genera are known to date, are a peculiar group of flightless, extinct anatids from theHawaiian Islands. Gigantic in size and with massive bills, they were believed to be geese, but have been shown to be actually very closely related tomallards. They evolved filling theecological niche ofturtles,ungulates, and othermegaherbivores.ACanada goose tucking its bill under its wing
Anas: pintails, mallards, etc. (40–50 living species, 3 extinct)
Chendytes, diving-geese (extinct c. 450–250 BCE, A basal member of the dabbling duck clade[16])
Tribe:Mergini, eiders, scoters, sawbills and other sea-ducksCommon goldeneye couple, male on the right (There are 9 extant genera and some 20 living species; most of this group occur in the Northern Hemisphere, but a few [mostly extinct] mergansers in the Southern Hemisphere)
Unresolved: The largest degree of uncertainty concerns whether a number of genera are closer to the shelducks or to the dabbling ducks.The rarewhite-winged duck, a species of unclear affiliationWood duckAix sponsa See also themonotypic subfamilies above, and the "perching ducks"
Coscoroba, coscoroba swan – Anserinae or same subfamily asCereopsis?
Cereopsis, Cape Barren goose – Anserinae, Tadorninae, or own subfamily?
Biziura, musk ducks (1 living species) - Oxyurini?
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 toCyanochen
Cairina andAsarcornis, Muscovy duck and white-winged duck, respectively (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? IncludesEuryanas.
Marmaronetta, marbled duck – formerly dabbling ducks; actually a diving duck or a distinct subfamily
Maned duck is the only living member of the genusChenonetta.
Fromsubfossil bones found onKauaʻi (Hawaiian Islands), two enigmatic waterfowl are known.[17] The living and assignable prehistoric avifauna of thearchipelago contains as AnseriformesBranta geese and their descendants, and themoa-nalos as mentioned above. The following taxa, although certainly new species, cannot be assigned even to subfamily; that Kauaʻi is the oldest of the large Hawaiian Islands, meaning the species may have been evolving in isolation for nearly 10 mya (since the LateMiocene), does not help in determining their affinities:
Long-legged "shelduck", Anatidae sp. et gen. indet.
Similarly,Branta rhuax from the Big Island ofHawaiʻi, and a gigantic goose-like anatid fromOʻahu are known only from very incomplete, and in the former case much damaged, bone fragments. The former has been alleged to be a shelduck,[18] but this was generally dismissed because of the damage to the material andbiogeographic considerations. The long-legged Kauaʻi bird, however, hints at the possibility of a former tadornine presence on the archipelago.
The fossil record of anatids is extensive, but many prehistoric genera cannot be unequivocally assigned to present-day subfamilies for the reasons given above. For prehistoric species of extant genera, see the respective genus accounts.
Dendrocheninae – a more advanced relative of the whistling-ducks or an ancestral relative of stifftail ducks paralleling whistling-ducks; if not extinct possibly belong in Oxyurinae (includingMalacorhynchus)
Mionetta (Late Oligocene – Middle Miocene of C Europe) – includes"Anas" blanchardi,"A." consobrina,"A." natator,"Aythya" arvernensis
Manuherikia (Bathans Early/Middle Miocene of Otago, New Zealand)
Aldabranas (Late Pleistocene of Aldabra, Indian Ocean) – anatine or tadornine*"Anas" albae (Late Miocene of Polgárdi, Hungary) – mergine? Formerly inMergus
"Anas" eppelsheimensis (Early Pliocene of Eppelsheim, Germany) – anatine?
"Anas" isarensis (Late Miocene of Aumeister, Germany) – anatine?
"Anas" luederitzensis (Kalahari Early Miocene of Lüderitzbucht, Namibia) – anatine?
"Anas" meyerii (Middle Miocene of Öhningen, Germany) Described from a single badly crushed tarsometatarsus and phalanges. This species was named in 1867 byMilne-Edwards and then recombined in 1964 byBrodkorb to the genusAythya. This species is currently regarded as Avesincertae sedis.[19]
"Anser" scaldii (Late Miocene of Antwerp, Belgium) – anserine or tadornine* Anatidae gen. et sp. indet. (Waite Late Miocene of Alcoota, Australia) – anatine, oxyurine?
"Anas" velox (Middle–Late? Miocene of C Europe) – anatine? May include"A." meyerii
Anatidae gen. et sp. indet. (Waite Late Miocene of Alcoota, Australia) – tadornine?
Anatidae gen. et sp. indet. MNZ S42797 (Bathans Early/Middle Miocene of Otago, New Zealand)
Anatidae gen. et sp. indet. (Middle Miocene of Nördlinger Ries, Germany) – tadornine?
Anatidae gen. et sp. indet. (Sajóvölgyi Middle Miocene of Mátraszõlõs, Hungary)[20]
"Aythya" chauvirae (Middle Miocene of Sansan, France and Credinţa, Romania) – 2 species
Caerulonettion (Early Miocene of France and the Czech Republic, Middle Miocene of Germany)
"Chenopis" nanus (Pleistocene of Australia) – at least 2 taxa, may be living species
The Middle OligoceneLimicorallus (fromChelkar-Teniz (Kazakhstan) was sometimes considered an anserine. It is now recognized as a primitivecormorant. The middle EoceneEonessa was formerly thought to belong to Anatidae, however reexamination of the holotype in 1978 resulted in the genus being placed as Avesincertae sedis.[1]
^abcCarboneras, Carles (1992): Family Anatidae (Ducks, Geese and Swans).In: del Hoyo, Josep; Elliott, Andrew & Sargatal, Jordi (eds.):Handbook of Birds of the World (Volume 1: Ostrich to Ducks): 536–629. Lynx Edicions, Barcelona.ISBN84-87334-10-5
^abcTodd, Frank S. (1991). Forshaw, Joseph (ed.).Encyclopaedia of Animals: Birds. London: Merehurst Press. pp. 81–87.ISBN1-85391-186-0.
^McKinney, Frank; Evarts, Susan (1998). "Sexual coercion in waterfowl and other birds".Ornithological Monographs.49 (49):165–193.doi:10.2307/40166723.JSTOR40166723.
^Briskie, James; Montgomerie, Robert (1997). "Sexual selection and the intromittent organ of birds".Journal of Avian Biology.28 (1):73–86.doi:10.2307/3677097.JSTOR3677097.
^Leach, William Elford (1819)."Eleventh Room".Synopsis of the Contents of the British Museum (15th ed.). London: British Museum. pp. 63–68 [67]. The name of the author is not specified in the document, Leach was the Keeper of Zoology at the time.
^Madge, Steve & Burn, Hilary (1987):Wildfowl : an identification guide to the ducks, geese and swans of the world.Christopher Helm, London.ISBN0-7470-2201-1
^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.
^Terres, John K. &National Audubon Society (NAS) (1991):The Audubon Society Encyclopedia of North American Birds. Wings Books, New York. Reprint of 1980 edition.ISBN0517032880
^Collar, N. J.; Andreev, A. V.; Chan, S.; Crosby, M. J.; Subramanya, S. & Tobias, J. A. (eds.) (2001):Pink-headed DuckArchived 2007-03-11 at theWayback Machine.In:Threatened Birds of Asia: The BirdLife International Red Data Book: 489–501. BirdLife International.ISBN0-946888-44-2
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