Grey Geese, Anser
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The grey geese are the genus Anser in the narrow sense. They are waterfowl belonging to the true geese and swan subfamily Anserinae. This genus contains species which are almost exclusively Eurasian in distribution, but at least one species is found in any place in the subarctic region in summer. They migrate north in winter, often to inland locations, and several species are found away from the coast all year round.
The white geese are sometimes placed here too, sometimes split off in the genus Chen. While they cannot be distinguished anatomically , they form a distinct lineage in evaluations of molecular data, and also differ in their biogeography, essentially replacing the white geese in Eurasia. The AOU is one notable ornithological organization which limits the genus Anser to the grey geese.
Anser as understood here (i.e. sensu AOU) contains 7-8 species which quite span the whole range of true geese shapes and sizes. They range from the appropriately named Swan Goose to the plump Bar-headed Goose and the tiny Lesser White-fronted Goose. All have legs that are of reddish, pink, or orange color, and many have such coloration on their bills also. All have white under- and uppertail coverts, and while most have some sort of white pattern on their heads, they are never entirely white-headed except for domestic breeds.
Living species
- Greylag Goose, Anser anser
- Domesticated goose, Anser anser domesticus
- White-fronted Goose, Anser albifrons
- Greenland White-fronted Goose, Anser albifrons flavirostris
- Lesser White-fronted Goose, Anser erythropus
- (Taiga) Bean Goose, Anser fabalis
- Tundra Bean Goose, Anser (fabalis) serrirostris
- Pink-footed Goose, Anser brachyrhynchus
- Bar-headed Goose, Anser indicus
- Swan Goose, Anser cygnoides
- Chinese Goose and African Goose, Anser cygnoides domesticus
Fossil record
Numerous fossil species have been allocated to this genus. As the true geese are near-impossible to assign osteologically to genus, this must be viewed with caution. It can be assumed with reasonable certainty that European fossils from known inland sites indeed belong into Anser. Given that 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 - while the genera Anser and Branta today do practically not coexist in freshwater habitat casts serious doubt on the correct generic assignment of the supposed North American fossil geese.
- Anser arenosus (Big Sandy Late Miocene of Wickieup, USA)
- Anser arizonae (Big Sandy Late Miocene of Wickieup, USA)
- Anser atavus (Late Miocene of Bavaria, Germany)
- Anser cygniformis (Late Miocene of Steinheim, Germany)
- Anser oeningensis (Late Miocene of Oehningen, Switzerland)
- Anser pratensis (Valentine Early Pliocene of Brown County, USA) - formerly Heterochen
- Anser pressus (Glenns Ferry Late Pliocene of Hagerman, USA) - formerly Chen pressa
- Anser thompsoni (Pliocene of Nebraska)
- Anser azerbaidzhanicus (Early Pleistocene of Binagada, Azerbaijan)
The giant Maltese swan Cygnus equitum was occasionally placed into Anser; Anser condoni is a synonym of Cygnus paloregonus (Brodkorb, 1964).
Copyright: Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from Wikipedia.org
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