Swan Goose

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Swan Goose
A Swan Goose in China
A Swan Goose in China
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Anseriformes
Family: Anatidae
Genus: Anser
Species: A. cygnoides
Binomial name
Anser cygnoides
(Linnaeus, 1758)
Synonyms

Cycnopsis cygnoides
Cygnopsis cygnoides

The Swan Goose Anser cygnoides is a large goose with a natural breeding range in Mongolia, northernmost China, and southeastern Russia. It is migratory and winters mainly in central and eastern China. The species has been domesticated, and introduced and feral populations occur elsewhere.[1]

It is large for its genus, 81–94 cm long (the longest Anser goose) and weighing 2.8–3.5 kg (the second-heaviest Anser, after the Greylag Goose). It has a long neck, long, heavy black bill, brown cap and pale underparts apart from some belly streaking; the upperparts are brown and the legs are orange. The sexes are similar, although the male is larger, and juveniles are duller. The voice is a loud honking. It grazes on sedges, and rarely swims. It forms small flocks outside the breeding season.[1]

It is a rare goose of steppes and mountain valleys, which breeds near marshes and other wetlands, laying 5–8 eggs in a ground nest. In the winter it grazes on steppes and stubble, sometimes far from water.[1]

The Swan Goose was listed as Endangered in the wild, the population declining due to habitat loss and excessive hunting[2], but new research has shown it to be not as rare as it was believed. Consequently, it is downlisted to Vulnerable status in 2008[3].

[edit] Domestication

Main article: Domesticated goose
Domesticated breeds of Chinese geese can be readily recognised by the knob on the beak, and the fat rear end.
Domesticated breeds of Chinese geese can be readily recognised by the knob on the beak, and the fat rear end.

The Swan Goose is extensively kept as poultry. A large number of breeds have been selected in captivity, known as Chinese goose. Chinese geese differ from the wild birds in much larger size (up to 5-10 kg in males, 4-9 kg in females, and in having an often strongly developed basal knob on the upper side of the bill. Some domesticated, introduced, or feral populations may be completely white, while others retain a plumage pattern more like wild birds. The knob at the top of the beak is more prominent on males than females. By 6–8 weeks of age, the knob is already pronounced enough that it can be used for sexing. The African geese are even heavier, with a noticeably plump neck and a pronounced dewlap in old birds; they have a conspicuously upright stance when on land.

Another Swan Goose breed, even more massive than Chinese geese, is known as the African goose[4]. Famed for their weight, African geese nonetheless have very lean meat, much more so than meat breeds of the Greylag Goose like Toulouse or Embden Geese. How exactly they relate to Africa is not known; though they are sometimes held to have been first bred in Guinea, their wild ancestors are doubtlessly the East Asian species and the common name may just be a tribute to their "exoticness".

A female Chinese goose can lay 50–60 eggs over the course of the breeding season (February to June), although there are reports of Chinese geese laying up to 100 eggs during that time.[5]

Charles Darwin studied goose breeds as part of his work on the theory of evolution. He noted that the external differences between Chinese geese and breeds descended from the Greylag Goose belied a rather close relationship:

"The hybrids from the common and Chinese geese (A. cygnoides), species which are so different that they are generally ranked in distinct genera[6], have often bred in this country with either pure parent, and in one single instance they have bred inter se."[7]

[edit] Footnotes

  1. ^ a b c Madge & Burn (1987), Carboneras (1992)
  2. ^ Carboneras (1992)
  3. ^ BLI (2008)
  4. ^ Feathersite.com - African Geese
  5. ^ Buckland & Guy (2002)
  6. ^ The Swan Goose had been separated in the monotypic genus Cygnopsis (alternatively spelled Cycnopsis) some 20 years before Darwin wrote this. Cygnopsis cygnoides essentially means "Swan lookalike", Cygnopsis signifying "looking like a swan" and cygnoides "similar to a swan".
  7. ^ Darwin (1859): p.253

[edit] References

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