|Greylag geese (pair), Anser anser|
The waterfowl genus Anser includes all grey geese (and sometimes the white geese). It belongs to the true geese and swan subfamily (Anserinae). 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 further south, reaching into warm temperate regions. They mostly migrate south in winter, typically to regions in the temperate zone between the January 0 °C (32 °F) to 5 °C (41 °F) isotherms.
The genus contains ten living species, which span nearly the whole range of true goose shapes and sizes. The largest is the greylag goose at 2.5–4.1 kg (5.5–9.0 lb) weight, and the smallest is the Ross's goose at 1.2–1.6 kg (2.6–3.5 lb). All have legs and feet that are pink, or orange, and bills that are pink, orange, or black. All have white under- and upper-tail coverts, and several 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 closely related "black" geese in the genus Branta differ in having black legs, and generally darker body plumage.
Systematics, taxonomy and evolution
Living species and taxonomy
- Swan goose Anser cygnoides – sometimes separated in Cygnopsis
- Taiga bean goose Anser fabalis
- Tundra bean goose Anser serrirostris
- Pink-footed goose Anser brachyrhynchus
- Greater white-fronted goose Anser albifrons
- Greenland white-fronted goose Anser (albifrons) flavirostris
- Lesser white-fronted goose Anser erythropus
- Greylag goose Anser anser
- Bar-headed goose Anser indicus – sometimes separated in Eulabeia
The following white geese are commonly separated as the genus Chen, with one of them sometimes split off in the genus Philacte. They cannot be distinguished anatomically from Anser geese although there is some evidence of a distinct lineage in evaluations of molecular data. While some ornithological works traditionally include Chen within Anser, the AOU is a notable authority that treat them as separate.
- Snow goose Chen caerulescens
- Ross's goose Chen rossii
- Emperor goose Chen canagicus – sometimes separated in Philacte
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 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. The Early Pliocene Branta howardae is one of the cases where doubts have been expressed about its generic assignment. Similarly, 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.[note 1]
- Anser atavus (Middle/Late Miocene of Bavaria, Germany) – sometimes in Cygnus
- Anser arenosus (Big Sandy Late Miocene of Wickieup, USA)
- Anser arizonae (Big Sandy Late Miocene of Wickieup, USA)
- Anser cygniformis (Late Miocene of Steinheim, Germany)
- Anser oeningensis (Late Miocene of Oehningen, Switzerland)
- Anser thraceiensis (Late Miocene/Early Pliocene of Trojanovo, Bulgaria)
- Anser pratensis (Valentine Early Pliocene of Brown County, USA) – possibly separable in Heterochen
- Anser pressus (Glenns Ferry Late Pliocene of Hagerman, USA) – formerly Chen pressa
- Anser thompsoni (Pliocene of Nebraska)
- Anser azerbaidzhanicus (Early? Pleistocene of Binagady, Azerbaijan)
The Maltese 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, and biogeography indicates Branta as other likely candidate.
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.
Most species are hunted to a greater or lesser extent; in some areas, some populations are endangered by over-hunting. Most notably, the lesser white-fronted goose is listed by IUCN Red List as Vulnerable throughout its range, and due to overhunting and rampant habitat destruction, the population of the swan goose is on the verge of collapsing, leading to a listing as Endangered.
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.
|Wikimedia Commons has media related to Anser.|
- Short (1970) considers this bird to be somewhat reminiscent of geese and swans, shelducks, and the "Cairinini" or "perching ducks". The latter are now known to be a paraphyletic assemblage of miscellaneous waterfowl the morphological similarities of which is the product of convergent evolution towards being able to perch in trees (Livezey 1986).
- Carboneras, 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, plates 40–50. Lynx Edicions, Barcelona. ISBN 84-87334-10-5
- Cramp, S. (1977): The Birds of the Western Palearctic. Oxford. ISBN 0-19-857358-8
- Madge, Steve & Burn, Hilary (1987): Wildfowl : an identification guide to the ducks, geese and swans of the world. Christopher Helm, London. ISBN 0-7470-2201-1
- Dudley, Steve P.; Gee, Mike; Kehoe, Chris; Melling, Tim M. & The British Ornithologists' Union Records Committee (2006). "The British List: A Checklist of Birds of Britain (7th edition)". Ibis 148 (3): 526–563. doi:10.1111/j.1474-919X.2006.00603.x.
- American Ornithologists' Union (1998): Check-list of North American Birds: the species of birds of North America from the Arctic through Panama, including the West Indies and Hawaiian Islands (7th ed., 41st supplement). American Ornithologists' Union and Allen Press, Washington, D.C. and Lawrence, Kansas, USA. ISBN 1-891276-00-X
- Banks, Richard C.; Chesser, R. Terry; Cicero, Carla; Dunn, Jon L.; Kratter, Andrew W.; Lovette, Irby J.; Rasmussen, Pamela C.; Remsen, J.V. Jr; Rising, James D. & Stotz, Douglas F. (2007). "Forty-eighth Supplement to the American Ornithologists' Union Check-List of North American Birds" (PDF). Auk 124 (3): 1109–1115. doi:10.1642/0004-8038(2007)124[1109:FSTTAO]2.0.CO;2.
- van den Berg, Arnoud B. (2007): Lijst van Nederlandse vogelsoorten ["List of Dutch bird taxa]. [Dutch and English] PDF fulltext
- Fox, A.D. & Stroud, D.A. (2002). "Greenland White-fronted Goose". Birds of the Western Palearctic Update 4 (2): 65–88.
- Brodkorb, Pierce (1964). "Catalogue of Fossil Birds: Part 2 (Anseriformes through Galliformes)". Bulletin of the Florida State Museum 8 (3): 195–335.
- Short, Lester L. (1970). "A new anseriform genus and species from the Nebraska Pliocene" (PDF). Auk 87 (3): 537–543. doi:10.2307/4083796.
- Livezey, Bradley C. (1986). "A phylogenetic analysis of recent anseriform genera using morphological characters" (PDF). Auk 103 (4): 737–754.
- A left humerus (specimen MUHNES 2SSAP30-853) and a left clavicle (specimen MUHNES 2SSAP30-545), apparently of a single bird: Cisneros, Juan Carlos (2005). "New Pleistocene vertebrate fauna from El Salvador" (PDF). Revista Brasileira de Paleontologia 8 (3): 239–255. doi:10.4072/rbp.2005.3.09.
- IUCN (2007): 2007 IUCN Red List of Threatened Species.