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Chen (genus)
Encyclopedia
The white geese are a small group of waterfowl
which are united in the genus
or subgenus
Chen, in the true geese
and swan
subfamily Anserinae
. They breed on subarctic
areas of North America
and around the Bering Strait
, migrating
south in winter.
Many authorities place these species
in the grey goose genus Anser
. Indeed, Chen and Anser are anatomically indistinguishable. However, external morphology
, biogeography
, and molecular data suggest that the white geese are indeed an evolution
ary lineage distinct from the grey geese – from which they split off fairly recently, essentially replacing them in North America. The AOU
recognizes this genus as distinct; most other authorities today consider it a subgenus
of Anser.
Like grey but unlike the Branta
black geese, their feet and legs are colored in reddish hues. The bill is also reddish in these birds as in most grey geese, except in adult males of Ross's Goose
which have a blue-black grainy cere
. The wingtips are black, as in all true geese, whereas the head is always white without any markings or pattern in adult birds of this genus, which distinguishes them from all other true geese except feral domesticated geese
. The rest of the plumage is either white all over, or colored in various dark bluish-grey hues; the latter birds, uniquely among true geese, do not have white uppertail and undertail coverts, though the tail itself may be white.
White-phase snow geese of both species can be told apart from feral geese best by the more slender, elegant neck, which is thick-set in domestic geese; these also have a generally heavier body and often lack black wingtips.
Species
The supposed fossil
dwarf snow goose Chen pressa is now placed in Anser (Brodkorb, 1964).
Waterfowl
Waterfowl are certain wildfowl of the order Anseriformes, especially members of the family Anatidae, which includes ducks, geese, and swans....
which are united in the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
or subgenus
Subgenus
In biology, a subgenus is a taxonomic rank directly below genus.In zoology, a subgeneric name can be used independently or included in a species name, in parentheses, placed between the generic name and the specific epithet: e.g. the Tiger Cowry of the Indo-Pacific, Cypraea tigris Linnaeus, which...
Chen, in the true geese
Goose
The word goose is the English name for a group of waterfowl, belonging to the family Anatidae. This family also includes swans, most of which are larger than true geese, and ducks, which are smaller....
and swan
Swan
Swans, genus Cygnus, are birds of the family Anatidae, which also includes 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...
subfamily Anserinae
Anserinae
The Anserinae is a subfamily in the waterfowl family Anatidae. It includes the swans and true geese. Under alternative systematical concepts , it is split into two subfamilies, the Anserinae containing the geese , while the Cygninae contain the swans.A number of other waterbirds, mainly related to...
. They breed on subarctic
Subarctic
The Subarctic is a region in the Northern Hemisphere immediately south of the true Arctic and covering much of Alaska, Canada, the north of Scandinavia, Siberia, and northern Mongolia...
areas of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
and around the Bering Strait
Bering Strait
The Bering Strait , known to natives as Imakpik, is a sea strait between Cape Dezhnev, Chukotka Autonomous Okrug, Russia, the easternmost point of the Asian continent and Cape Prince of Wales, Alaska, USA, the westernmost point of the North American continent, with latitude of about 65°40'N,...
, migrating
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
south in winter.
Many authorities place these species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
in the grey goose genus Anser
Anser (genus)
The waterfowl genus Anser includes all grey geese and sometimes the white geese. It belongs to the true geese and swan subfamily . 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...
. Indeed, Chen and Anser are anatomically indistinguishable. However, external morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
, biogeography
Biogeography
Biogeography is the study of the distribution of species , organisms, and ecosystems in space and through geological time. Organisms and biological communities vary in a highly regular fashion along geographic gradients of latitude, elevation, isolation and habitat area...
, and molecular data suggest that the white geese are indeed an evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
ary lineage distinct from the grey geese – from which they split off fairly recently, essentially replacing them in North America. The AOU
American Ornithologists' Union
The American Ornithologists' Union is an ornithological organization in the USA. Unlike the National Audubon Society, its members are primarily professional ornithologists rather than amateur birders...
recognizes this genus as distinct; most other authorities today consider it a subgenus
Subgenus
In biology, a subgenus is a taxonomic rank directly below genus.In zoology, a subgeneric name can be used independently or included in a species name, in parentheses, placed between the generic name and the specific epithet: e.g. the Tiger Cowry of the Indo-Pacific, Cypraea tigris Linnaeus, which...
of Anser.
Like grey but unlike the Branta
Branta
The black geese of the genus Branta are waterfowl belonging to the true geese and swans subfamily Anserinae. They occur in the northern coastal regions of the Palearctic and all over North America, migrating to more southernly coasts in winter, and as resident birds in the Hawaiian Islands...
black geese, their feet and legs are colored in reddish hues. The bill is also reddish in these birds as in most grey geese, except in adult males of Ross's Goose
Ross's Goose
The Ross's Goose is a North American species of goose.The American Ornithologists' Union places this species and the other two "white" geese in the genus Chen rather than the more traditional "grey" goose genus Anser.This goose breeds in northern Canada, mainly in the Queen Maud Gulf Migratory...
which have a blue-black grainy cere
Cère
The Cère is a long river in south-western France, left tributary of the Dordogne River. Its source is in the south-western Massif Central, near the mountain Plomb du Cantal...
. The wingtips are black, as in all true geese, whereas the head is always white without any markings or pattern in adult birds of this genus, which distinguishes them from all other true geese except feral domesticated geese
Domesticated goose
Domestic geese are domesticated Grey geese kept as poultry for their meat, eggs, and down feathers since ancient times.-Origins and characteristics:...
. The rest of the plumage is either white all over, or colored in various dark bluish-grey hues; the latter birds, uniquely among true geese, do not have white uppertail and undertail coverts, though the tail itself may be white.
White-phase snow geese of both species can be told apart from feral geese best by the more slender, elegant neck, which is thick-set in domestic geese; these also have a generally heavier body and often lack black wingtips.
Species
- Snow GooseSnow GooseThe Snow Goose , also known as the Blue Goose, is a North American species of goose. Its name derives from the typically white plumage. The genus of this bird is disputed...
, Chen caerulescens - Ross's GooseRoss's GooseThe Ross's Goose is a North American species of goose.The American Ornithologists' Union places this species and the other two "white" geese in the genus Chen rather than the more traditional "grey" goose genus Anser.This goose breeds in northern Canada, mainly in the Queen Maud Gulf Migratory...
, Chen rossii - Emperor GooseEmperor GooseThe Emperor Goose is a species of goose. It breeds around the Bering Sea, mostly in Alaska, USA, but also in Kamchatka, Russia...
, Chen canagica
The supposed fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
dwarf snow goose Chen pressa is now placed in Anser (Brodkorb, 1964).