The Anatidae are the biological family of water birds that includes ducks, geese, and swans. The family has a cosmopolitan distribution, occurring on all the world's continents. These birds are adapted for swimming, floating on the water surface, and in some cases diving in at least shallow water. The family contains around 146 species in 43 genera. (The magpie 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 are monogamous breeders. A number of species undertake annual 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 are threatened with extinction.
|Clockwise from top left: mallard, mute swan, Brazilian teal, paradise shelduck, bufflehead, and greylag goose.|
The ducks, geese, and swans are small- to large-sized birds with a broad and elongated general body plan. Diving species vary from this in being rounder. Extant species range in size from the cotton pygmy goose, at as little as 26.5 cm (10.5 in) and 164 g (5.8 oz), to the trumpeter swan, at as much as 183 cm (6 ft) and 17.2 kg (38 lb). The wings are short and pointed, and supported by strong wing muscles that generate rapid beats in flight. 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 as grebes or petrels. They typically have webbed feet, though a few species such as the Nene 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 serrated lamellae which are particularly well defined in the filter-feeding species.
Their feathers are excellent at shedding water due to special oils. Many of the ducks display sexual dimorphism, with the males being more brightly coloured than the females (although the situation is reversed in species such as the paradise 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.
Anatids are generally herbivorous as adults, feeding on various water-plants, although some species also eat fish, molluscs, or aquatic arthropods. One group, the mergansers, are primarily piscivorous, 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.
The anatids are generally seasonal and monogamous 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, forced extrapair copulation among anatids are common, ocucurring in 55 species in 17 genera.
Anatidae is a large proportion of the 3% of bird species to possess a penis, though they vary significantly in size, shape, and surface elaboration. Most species are adapted for copulation 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 female incubates the eggs. The young are precocial, and are able to feed themselves from birth. One aberrant species, the black-headed duck, is an obligate brood parasite, laying its eggs in the nests of gulls and coots. 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 are damaging agricultural pests, and have acted as vectors for zoonoses such as avian influenza.
Since 1600, five species of ducks have become extinct due to the activities of humans, and subfossil remains have shown that humans caused numerous extinctions in prehistory. Today, many more are considered threatened. Most of the historic and prehistoric extinctions were insular species, vulnerable due to small populations (often endemic to a single island), and island 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 and introduced species. Other extinctions and declines are attributable to overhunting, habitat loss and modification, and hybridisation with introduced ducks (for example the introduced ruddy duck swamping the white-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 family Anatidae was introduced by the English zoologist William Elford Leach in a guide to the contents of the British Museum published in 1820. 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, a study of anatomical characters by Livezey suggests the Anatidae are better treated in nine subfamilies. This classification was popular in the late 1980s to 1990s. But mtDNA sequence analyses indicate, for example, the dabbling and diving ducks do not belong in the same subfamily.
While shortcomings certainly occur in Livezey's analysis, mtDNA is an unreliable source for phylogenetic information in many waterfowl (especially dabbling ducks) due to their ability to produce fertile hybrids, in rare cases possibly even beyond the level of genus (see for example the "Barbary duck"). Because the sample 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 robust phylogeny is still lacking, the reasons for the confusing data are at least clear: As demonstrated by the Late Cretaceous fossil Vegavis 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 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, the Anatidae may be considered to consist of three 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.
From subfossil bones found on Kauaʻi (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 Kauaʻi is the oldest of the large Hawaiian Islands, meaning the species may have been evolving in isolation for nearly 10 mya (since the Late Miocene), does not help in determining their affinities:
Similarly, Branta rhuax from the Big Island of Hawaiʻi, and a gigantic goose-like anatid from Oʻahu are known only from very incomplete, and in the former case much damaged, bone fragments. The former has been alleged to be a shelduck, but this was generally dismissed because of the damage to the material and biogeographic 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 (including Malacorhynchus)
Putative or disputed prehistoric anatids are:
The Middle Oligocene Limicorallus (from Chelkar-Teniz (Kazakhstan) was sometimes considered an anserine. It is, however, a primitive cormorant. The middle Eocene Eonessa was formerly thought to belong to Anatidae, however reexamination of the holotype in 1978 resulted in the genus being placed as Aves incertae sedis.
The Anatinae are a subfamily of the family Anatidae (swans, geese and ducks). Its surviving members are the dabbling ducks, which feed mainly at the surface rather than by diving. The other members of the Anatinae are the extinct moa-nalo, a young but highly apomorphic lineage derived from the dabbling ducks.
There has been much debate about the systematical status and which ducks belong to the Anatinae. Some taxonomic authorities only include the dabbling ducks and their close relatives, the extinct moa-nalos. Alternatively, the Anatinae are considered to include most "ducks", and the dabbling ducks form a tribe Anatini within these. The classification as presented here more appropriately reflects the remaining uncertainty about the interrelationships of the major lineages of Anatidae (waterfowl).Anseriformes
Anseriformes is an order of birds that comprise about 180 living species in three families: Anhimidae (the 3 screamers), Anseranatidae (the magpie goose), and Anatidae, the largest family, which includes over 170 species of waterfowl, among them the ducks, geese, and swans. Most modern species in the order are highly adapted for an aquatic existence at the water surface. With the exception of screamers, all have phalli, a trait that has been lost in the Neoaves. Due to their aquatic nature, most species are web-footed.Anserinae
The Anserinae are a subfamily in the waterfowl family Anatidae. It includes the swans and true geese. Under alternative systematical concepts (see e.g., Terres & NAS, 1991), it is split into two subfamilies, the Anserinae contain the geese and the ducks, while the Cygninae contain the swans.Australian shelduck
The Australian shelduck (Tadorna tadornoides), also known as the chestnut-breasted shelduck or mountain duck, is a shelduck part of the bird family Anatidae. The genus name Tadorna comes from Celtic roots and means "pied waterfowl". They are protected under the National Parks and Wildlife Act, 1974.Diving duck
The diving ducks, commonly called pochards or scaups, are a category of duck which feed by diving beneath the surface of the water. They are part of Anatidae, the diverse and very large family that includes ducks, geese, and swans.
The diving ducks are placed in a distinct tribe in the subfamily Anatinae, the Aythyini. While morphologically close to the dabbling ducks, there are nonetheless some pronounced differences such as in the structure of the trachea. mtDNA cytochrome b and NADH dehydrogenase subunit 2 sequence data indicate that the dabbling and diving ducks are fairly distant from each other, the outward similarities being due to convergent evolution.
Alternatively, the diving ducks are placed as a subfamily Aythyinae in a subfamily Anatidae which would encompass all duck-like birds except the whistling-ducks.
The seaducks commonly found in coastal areas, such as the long-tailed duck (formerly known in the US as oldsquaw), scoters, goldeneyes, mergansers, bufflehead and eiders, are also sometimes colloquially referred to in North America as diving ducks because they also feed by diving; their subfamily (Merginae) is a very distinct one however.
Although the group is cosmopolitan, most members are native to the Northern Hemisphere, and it includes several of the most familiar Northern Hemisphere ducks.
This group of ducks is so named because its members feed mainly by diving, although in fact the Netta species are reluctant to dive, and feed more like dabbling ducks.
These are gregarious ducks, mainly found on fresh water or on estuaries, though the greater scaup becomes marine during the northern winter. They are strong fliers; their broad, blunt-tipped wings require faster wing-beats than those of many ducks and they take off with some difficulty. Northern species tend to be migratory; southern species do not migrate though the hardhead travels long distances on an irregular basis in response to rainfall. Diving ducks do not walk as well on land as the dabbling ducks; their legs tend to be placed further back on their bodies to help propel them when underwater.Duck
Duck is the common name for a large number of species in the waterfowl family Anatidae which also includes swans and geese. Ducks are divided among several subfamilies in the family Anatidae; they do not represent a monophyletic group (the group of all descendants of a single common ancestral species) but a form taxon, since swans and geese are not considered ducks. Ducks are mostly aquatic birds, mostly smaller than the swans and geese, and may be found in both fresh water and sea water.
Ducks are sometimes confused with several types of unrelated water birds with similar forms, such as loons or divers, grebes, gallinules, and coots.Eonessa
Eonessa is an enigmatic genus of bird possibly belonging to bird order Gruiformes and which consists of the single species Eonessa anaticula.It was first described by Alexander Wetmore in the Journal of Paleontology in May 1938. In his paper, Wetmore erected the Anatidae subfamily Eonessinae, and placed Eonessa as the oldest Anatidae genus in the fossil record. This placement was possibly due to a resemblance to the modern ruddy duck (Oxyura jamaicensis), although Wetmore did not explain his taxonomic placement in the describing paper.Restudy of the holotype specimen in 1978 by Storrs Olson and Alan Feduccia resulted in the removal of Eonessa from Anatidae. Olson and Feduccia placed the genus as Aves incertae sedis noting it was possibly a member of the polymorphic order Gruiformes. The holotype was collected on August 26, 1936 from the Myton Pocket, Duchesne County, Utah, USA. The quarry is on the Myton Member of the Uinta Formation and dates to the Middle Eocene, around 46-42 million years ago.Now in the Princeton University paleontology collections as specimen number 14399, the holotype and only known specimen is a 13 cm (5 in) long partial wing, consisting of metacarpals down to the partial humerus. Though found articulated, the bones were badly crushed during fossilization. The bones, after further matrix removal in the 1970s, are very slender and with little diagnostic detail and little to no similarity to modern Anatidae members. The general proportions are closer to Gruiformes birds that have been found in the same rock formations, however the lack of detail does not allow firm placement into the order.Goose
A goose (plural geese) is a bird of any of several waterfowl species in the family Anatidae. This group comprises the genera Anser (the grey geese), Branta (the black geese), and Chen (which includes the white geese); the latter being commonly placed within the genus Anser. Some other birds, mostly related to the shelducks, have "goose" as part of their names. More distantly related members of the family Anatidae are swans, most of which are larger than true geese, and ducks, which are smaller.
The term "goose" is more properly used for a female bird, while "gander" refers specifically to a male one. Young birds before fledging are called goslings. The collective noun for a group of geese on the ground is a gaggle; when in flight, they are called a skein, a team, or a wedge; when flying close together, they are called a plump.Horned screamer
The horned screamer (Anhima cornuta) is a member of a small family of birds, the Anhimidae, which occurs in wetlands of tropical South America. There are three screamer species, the other two being the southern screamer and the northern screamer in the genus Chauna. They are related to the ducks, geese and swans, which are in the family Anatidae, but have bills looking more like those of game birds.List of endemic birds of Hawaii
There are 71 known taxa of birds endemic to the Hawaiian Islands, of which 30 are extinct, 6 possibly extinct and 30 of the remaining 48 species and subspecies are listed as endangered or threatened by the United States Fish and Wildlife Service. Habitat loss and avian disease are thought to have had the greatest effect on endemic bird species in Hawaii.Mute swan
The mute swan (Cygnus olor) is a species of swan and a member of the waterfowl family Anatidae. It is native to much of Eurasia, and (as a rare winter visitor) the far north of Africa. It is an introduced species in North America, Australasia and southern Africa. The name 'mute' derives from it being less vocal than other swan species. Measuring 125 to 170 cm (49 to 67 in) in length, this large swan is wholly white in plumage with an orange beak bordered with black. It is recognisable by its pronounced knob atop the beak, which is larger in males.Paradise shelduck
The paradise shelduck (Tadorna variegata) is a large goose-like duck endemic to New Zealand. It is a shelduck, a group of large goose-like birds which are part of the bird family Anatidae. The genus name Tadorna comes from Celtic roots and means "pied waterfowl".
Known to the Māori as pūtangitangi, but now commonly referred to as the "paradise duck", it is a prized game bird. Both the male and female have striking plumage: the male has a black head and barred black body, the female a white head with a chestnut body.The paradise shelducks usually live as pairs, grazing on grass and weeds, and will raid crops, particularly when molting.Screamer
The screamers are a small family, Anhimidae, of South American birds. For a long time, they were thought to be most closely related to the Galliformes because of similar bills, but they are instead more closely related to ducks (family Anatidae), most closely to the magpie goose (which some DNA evidence suggests are closer to screamers than to ducks). The clade is exceptional within the living birds in lacking uncinate processes of ribs. The screamers are represented by three species, the horned screamer (Anhima cornuta), the southern screamer or crested screamer (Chauna torquata) and the northern screamer or black-necked screamer (Chauna chavaria). A penis is absent in the males, and the birds' skin has a layer about a quarter of an inch thick, filled with small bubbles of air, which produce a crackling sound when pressed.Shelduck
The shelducks, most species of which are found in the genus Tadorna (except for the Radjah shelduck, which is now found in its own monotypic genus Radjah), are a group of large birds in the Tadorninae subfamily of the Anatidae, the biological family that includes the ducks and most duck-like waterfowl such as the geese and swans.Spur-winged goose
The spur-winged goose (Plectropterus gambensis) 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. It occurs in wetlands throughout sub-Saharan Africa.Swan
Swans are birds of the family Anatidae within the genus Cygnus. The swans' closest relatives include the 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. There are six or seven living (and one extinct) species of swan in the genus Cygnus; in addition, there is another species known as the coscoroba swan, although this species is no longer considered one of the true swans. Swans usually mate for life, although “divorce” sometimes occurs, particularly following nesting failure, and if a mate dies, the remaining swan will take up with another. The number of eggs in each clutch ranges from three to eight.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.
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.Whistling duck
The whistling ducks or tree ducks are a subfamily, Dendrocygninae, of the duck, goose and swan family of birds, Anatidae. They are not true ducks. In other taxonomic schemes, they are considered a separate family, Dendrocygnidae. Some taxonomists list only one genus, Dendrocygna, which contains eight living species, and one undescribed extinct species from Aitutaki of the Cook Islands, but other taxonomists also list the white-backed duck (Thalassornis leuconotus) under the subfamily.White-backed duck
The white-backed duck (Thalassornis leuconotus) is a waterbird of the family Anatidae. It is distinct from all other ducks, but most closely related to the whistling ducks in the subfamily Dendrocygninae, though also showing some similarities to the stiff-tailed ducks in the subfamily Oxyurinae. It is the only member of the genus Thalassornis.