Gray headed goose
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Gray-headed goose ( Chloephaga poliocephala ) |
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| Chloephaga poliocephala | ||||||||||||
| Sclater , 1857 |
The gray-headed goose ( Chloephaga poliocephala ) is a South American bird and belongs to the family of ducks (Anatidae). It is one of the half geese and has the goose-like habit that is characteristic of this subfamily. Similar to the Magellan goose, the gray-headed goose is seen as a food competitor for domestic animals. The wheat-growing areas in the province of Buenos Aires are among their most important wintering spots. It is therefore subject to a corresponding hunting pressure. Overall, the species is considered widespread, but not common.
The first scientific description was made in 1857 by Philip Lutley Sclater using a specimen collected on Chiloé .
features
The gray-headed goose reaches a body size of 50 to 55 centimeters. Unlike the Magellanic and Kelp goose belonging to the same genus , the gray-headed goose does not show any pronounced sexual dimorphism . Ganter can only be recognized by their slightly larger body. The males weigh an average of 2.26 kilograms, the females are on average almost 60 grams lighter. The significantly longer wings of the males are particularly striking.
In adult status, the gray-headed goose has a gray head. The base of the neck is gray and runs over in the front area into a chestnut-brown plumage, which is colored gray-brown towards the rear. The flanks of the plumage, offset by black lines, are white. Legs and feet are orange-red and the beak gray-black. In contrast to the adult birds, the young have a brownish plumage on the head and at the base of the neck. Almost nothing is known about the moulting pattern of wild species. Gray-headed geese kept in Europe often show moulting problems, so that insufficient knowledge about the natural moulting process can be obtained from them. Young birds are already largely similar to the adult gray-headed geese, but they are drawn more transversely on the underside of the body.
There is a gender difference in the voice. The females give a loud, deep cackle while the males whisper softly and softly.
distribution and habitat
The distribution area is in the mountainous regions in the south of South America , among others in Chile and Argentina as well as on the Falkland Islands. However, it is only an irregular breeding bird in the Falkland Islands. The first evidence of successful breeding on the Falkland Islands comes from 1985, the second from 1992. Overall, individual birds seem to only occasionally drift during the migration to the Falkland Islands and then occasionally also breed.
The habitat of the gray-headed goose is grassland in river valleys, at lakes and marshland as well as on the coast.
Way of life
The way of life of the gray-headed geese differs only slightly from that of the Magellan goose and the red-headed goose . However, their habitat are river and stream valleys, wooded bogs and forest swamps, in which the other two species do not occur. Gray-headed geese are territorial animals that occupy large territories. Their food crops are grasses, herbs and marsh plants. In their winter quarters they also eat seeds and crops.
The courtship is triggered by the male, whose courtship poses include strong bowing movements in the direction of the female. The female reacts to this with a very upright posture that brings out the white-colored belly. Males are extremely aggressive during this time. Conspecifics and other geese are attacked with their heads bowed in a pose reminiscent of geese. The wings are also used to hit the opponent. After successfully defending the breeding ground, the male returns to the female and starts a cry of triumph , as is also found, for example, in the gray goose.
The nest is built in tall grass and padded with feathers. The clutch consists of four to six eggs and is hatched over a period of 30 days.
attitude
The gray-headed goose was first kept in zoos in 1833. The zoo in London succeeded in breeding as early as 1852. The attractively colored half-goose species has since been shown in zoos. Overall, however, the number of gray-headed geese in European zoos has declined due to the increased focus on Nordic geese species, which are more threatened.
supporting documents
literature
- Janet Kear (Ed.): Ducks, Geese and Swans. Oxford University Press, 2005, ISBN 0-19-854645-9 .
- Hartmut Kolbe: The world's ducks. Ulmer Verlag 1999, ISBN 3-8001-7442-1 .
- Hadoram Shirihai: A Complete Guide to Antarctic Wildlife - The Birds and Marine Mammals of the Antarctic Continent and Southern Ocean. Alula Press, Degerby 2002, ISBN 951-98947-0-5 .
- Robin and Anne Woods: Atlas of Breeding Birds of the Falkland Islands. Anthony Nelson, Shorpshire 1997, ISBN 0-904614-60-3 .
Web links
- Chloephaga poliocephala in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed January 2 of 2009.
- Videos, photos and sound recordings of Chloephaga poliocephala in the Internet Bird Collection