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Anser is a waterfowl genus that includes the grey geese and the white geese. It belongs to the true goose and swan subfamily of Anserinae under the family of Anatidae. The genus has a Holarctic distribution, with at least one species breeding in any open, wet habitats in the subarctic and cool temperate regions of the Northern Hemisphere in summer. Some also breed farther south, reaching into warm temperate regions. They mostly bird migration south in winter, typically to regions in the temperate zone between the January 0 °C (32 °F) and 5 °C (41 °F) isotherms.
The genus contains 11 living species.
All have legs and feet that are pink or orange, and bills that are pink, orange, black, or patterned in a combination of these colours. All have white under- and upper-tail coverts, and some have some extent of white on their heads. The neck, body and wings are grey or white, with black or blackish primary—and also often secondary—remiges (pinions). The three species of "white geese" (emperor goose, snow goose and Ross's geese) were formerly treated as a separate genus Chen, but are now generally included in Anser, as their exclusion would leave Anser paraphyly with the bar-headed goose A. indicus being basal in the genus. The closely related "black" geese in the genus Branta differ in having black legs, and generally darker body plumage.
| Breeds in highlands of Central Asia; winters in South Asia, Myanmar and southern China; introduced in Europe |
| Near the Pacific coast in Alaska, Russian Far East and Canada |
| Breeds in northern Canada and Alaska; winters in contiguous United States and northern Mexico |
| Breeds in northern Canada, Alaska and Greenland; winters in contiguous United States and northern Mexico |
| Europe, Asia and North Africa |
| Breeds in Mongolia, northernmost China and southeastern Russia; winters in southeastern China |
| Breeds in Russia, Finland, Norway and Sweden; winters in Europe, and Central and East Asia |
| Breeds in Iceland, Svalbard and Greenland; winters in northwestern Europe |
| Breeds in northern Russia; winters in Europe, and Central and East Asia |
| Breeds in northern Canada, Alaska, Greenland and northern Russia; winters in contiguous United States, northern Mexico, Europe, East Asia, Iraq and near the Caspian Sea |
| Breeds in northern Russia, Finland, Norway and Sweden; winters in East Asia, near the Caspian Sea, and in southeastern and northwestern Europe |
Some authorities also treat some subspecies as potential future species splits, notably the Greenland white-fronted goose A. albifrons flavirostris. The three east Asian subspecies of the bean goose complex (currently treated as A. fabalis johanseni, A. fabalis middendorfii, and A. serrirostris serrirostris) also await genetic analysis to discern their affinities.
The Malta swan Cygnus equitum was occasionally placed into Anser, and Anser condoni is a synonym of Cygnus paloregonus. A goose fossil from the early-middle Pleistocene of El Salvador is highly similar to Anser; given its age it is likely to belong to an extant genus, though biogeography indicates Branta as another potential candidate.
Anser scaldii Beneden 1872 nomen nudum (Late Miocene of Antwerp, Belgium), based on a right humerus, was reassigned to the modern Brent goose and suggested to be reworked from later Pleistocene or Holocene deposits.
Most species are hunted to a greater or lesser extent; in some areas, some populations are threatened by over-hunting and habitat loss. Although most species are not considered threatened by the IUCN, the lesser white-fronted goose and swan goose are listed as Vulnerable and the emperor goose is near-threatened.
Other species have benefited from reductions in hunting since the late 19th and early 20th centuries, with most species in western Europe and North America showing marked increases in response to protection. In some cases, this has led to conflicts with farming, when large flocks of geese graze crops in the winter.
Fossil record
Numerous fossil species have been allocated to this genus. As the true geese are near-impossible to assign osteology to genus, this must be viewed with caution. It can be assumed with limited certainty that European fossils from known inland sites belong into Anser. As species related to the Canada goose have been described from the Late Miocene onwards in North America too, sometimes from the same localities as the presumed grey geese, it casts serious doubt on the correct generic assignment of the supposed North American fossil geese. Heterochen = Anser pratensis seems to differ profoundly from other species of Anser and might be placed into a different genus; alternatively, it might have been a unique example of a grey goose adapted for perching in trees.Short (1970) considers this bird to be somewhat reminiscent of geese and swans, , and the Cairinini or "perching ducks".The Cairinini or "perching ducks" are now known to be a paraphyletic assemblage of miscellaneous waterfowl whose morphological similarities are the product of convergent evolution towards being able to perch in trees (Livezey 1986).
Relationship with humans and conservation status
Two species in the genus are of major commercial importance, having been domesticated as poultry: European domesticated geese are derived from the greylag goose, and Chinese and some African domesticated geese are derived from the swan goose.
See also
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