Australian kasarka
| Australian kasarka | ||||||||||||
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Australian kasarka |
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| Scientific name | ||||||||||||
| Tadorna tadornoides | ||||||||||||
| ( Jardine & Selby , 1828) |
The Australian kasarka or collar kasarka ( Tadorna tadornoides ) is a species from the duck family . It belongs to the half geese that stand between the real geese and the real ducks. The distribution area of this Kasarka species is the southeast and southwest of Australia and Tasmania . There are also random visitors to New Zealand.
Appearance
Australian kasarkas are large demi-geese. The body length of the males is between 59 and 72 centimeters. The females, on the other hand, have a body length between 56 and 98 centimeters. The wingspan of the males is 96 to 132 centimeters, while that of the females is between 94 and 116 centimeters. They weigh between 1.3 and 1.6 kilograms.
Australian kasarkas show a definite sexual dimorphism . In their splendid plumage, males have a strong, clay-brown breast and a dark head. Feet and legs are dark gray. The eyes are brown. When resting, the Australian Kasarka has only a little less contrasting plumage. In the male, the breast color is pale clay brown during this time instead of a strong clay brown. The white neck ring is narrower and less sharply set off from the adjacent dark plumage.
The female is smaller than the male and has an uneven, white eye ring. The base of the beak is also white. A thin white band on the lower part of the neck is characteristic of both sexes. In females it is often not very noticeable and can also be completely absent in individual female individuals. When resting, the female's plumage is a little lighter overall.
Australian Kasarkas moult their plumage twice a year. During the moult, which takes place after the breeding season, they usually change all flight feathers and are then temporarily unable to fly. At the second moult, which begins about six months later, they only change the small plumage and show the breeding plumage about two months later.
Young kazarkas change into their first annual dress at the age of seven months. In both sexes, this plumage is a little darker and flatter in color than in the adult birds. The large wing covers are still gray throughout in this dress.
Possible confusion with other species
In Australia, Australian Kasarkas cannot be confused with any other species. Due to their strong body and their relatively small head, their upright posture and their legs set far forward, they can be reliably identified from a distance. The white collar and the chestnut chest also contrast strikingly with the rest of the body's plumage. No other bird species in Australia has such plumage coloring. The maned goose is significantly smaller and has a longer neck in relation to its body size. Due to their conspicuously different plumage coloring, they can only be confused if visibility is very poor. The Radjahgans is related to the Australian Kasarka, but it is also significantly smaller and unmistakable due to its white head.
In New Zealand, where Australian Kasarkas occasionally appear regularly as a stray visitor, there is a possibility of confusion with the Paradise Kasarka . Especially the males and the young birds of the Paradise Kasarka can be confused with the Australian Kasarka | Australian Kasarka with their dark head and neck, which resembles the Paradise Kasarka in body size, shape and posture. The Paradise Kasarka, however, lacks the white collar and, unlike the Australian Kasarka, has a plain dark underside.
The greatest possibility of confusion is between the female of the Australian Kasarkas and young females of the Paradise Kasarkas, which are changing their body plumage to the adult female. In these, the white head and neck are not yet very pronounced. Young female Paradise Kasarkas can also be distinguished from the Australian Kasarkas by the lack of a white collar and the dark and non-chestnut-colored undercovers.
Distribution area and existence
Australian kazarkas are endemic to Australia . Their range is disjoint. They are only common in part of southwest Australia as well as in the southeast and Tasmania. They show wandering movements, which, however, have no clear direction of movement. The waters where they spend their moulting change depending on the environmental conditions. Their migratory movements are in response to droughts and heavy rainfall.
The species occurs as a stray visitor on New Zealand and some sub-Antarctic islands, but usually does not breed there. In New Zealand, it is observed on both the South and North Islands. The birds observed are mostly small groups. The number of birds observed increases when drought prevails in some regions in Australia. The number of birds observed was very large in 1982 and 1983 when the weather conditions there were adequate. There is also evidence of breeding for 1985, which suggests that Australian Kasarkas can colonize other areas at least for a short time.
Habitat and diet
Australian kazarkas are goose birds of the temperate climate zone. They are usually found south of 30 ° S in Eastern Australia, but only up to 25 ° S in Western Australia.
Australian kasarkas are bound to fresh water and prefer to inhabit the edge zones of large shallow waters. They can also occasionally be seen in pasture areas and agricultural cultivation areas. Basically, they prefer open, easily overlooked areas that are at best isolated with trees. In Australia, they are also increasingly breeding at artificially created water holes. Deforestation to create pasture and cultivation areas has basically contributed to the fact that their population numbers have increased in some regions. They find their food both on pastures and in shallow water and, like the shelduck , which is related to them, also look for food on the alluvial surfaces along the coast. Most often, however, they can be observed while grazing and are often at a greater distance from the nearest body of water.
Australian Kasarkas show a loyalty to the breeding site, but are adaptable with regard to their moulting places. Tasmanian breeding birds migrate several hundred kilometers to Australia to molt there.
Reproduction
Australian kasarkas enter into a monogamous couple relationship. Long-term partner loyalty has been observed in some individuals, but a change in the partner bird has been observed in the age groups. There is a tendency for individuals who have not incubated successfully to change partners, and relationships that are formed by young birds rarely last longer than three months. Australian Kasarkas already bond at an age of five to six months. Usually they are at least 22 months old before they breed for the first time.
The breeding season of the Kazarkas begins in March and April when the winter rainy season sets in in Australia. Australian kasarkas are cave breeders. They mostly use tree hollows, but also create their breeding holes in caves in rock walls and earthworks. Suitable breeding sites are used repeatedly. The choice of the nesting location is made by both sexes, it is not necessarily in the territory in which the parent birds raise their offspring. The nest distance is at least ten meters. The eggs are laid between mid-June and late September. Clutches contain between five and 14 eggs, each weighing an average of about 88 grams. Only the female breeds, but the male stays close to the female during the breeding season and accompanies her when it visits foraging grounds during the breeding breaks. The breeding season is between 30 and 33 days. The dune pups are led by both parent birds. Australian kasarkas are sexually mature around the age of 2 years.
The New Holland crow and the herring head gull are among the predators of eggs and juveniles . Numerous young birds die when the parent birds move with them from the nesting site to the feeding ground. Some of the young birds are lost or die of exhaustion. They are also hit by feral domestic cats and possibly foxes. Unfavorable weather conditions also significantly increase the death rates of young birds.
Outside the breeding season, the Australian Kasarkas form large groups. These are very rich in individuals, especially during the moulting season. Antagonistic behavior can only be observed in these troops when young birds join in and begin courtship behavior. In grazing troops, couples who have successfully brooded tend to stay with their offspring at the sides of the troop. In the middle, on the other hand, are the unmated adults, not yet sexually mature young birds and the couples without offspring.
Systematics
The Australian Kasarka belongs to the demi-geese, a subfamily to which the species shelduck and rust- goose, which also occur in Central Europe, belong. Characteristic of the species in this subfamily is the geese-like habitus. A number of characteristics of the half geese can also be found in the group of actual ducks .
Attitude in Europe
Australian kasarkas have been featured in European zoos since 1860. The first owner was the zoo in London . In 1872 the Berlin Zoological Garden also acquired this type of Kasarka. However, the first offspring in Europe did not take place until 1939. In the USA, the species was not successfully bred for the first time until 1962. Today all Australian Kasarkas shown in European zoos come from bred ones, as Australia has not allowed the export of wild animals for some time.
literature
- PJ Higgins (Eds.): Handbook of Australian, New Zealand & Antarctic Birds , Volume 1, Ratites to Ducks, Oxford University Press, Oxford 1990, ISBN 0-19-553068-3
- Janet Kear (Ed.): Ducks, Geese and Swans. Oxford University Press, 2005, ISBN 0-19-854645-9 .
- Hartmut Kolbe; Die Entenvögel der Welt , Ulmer Verlag 1999, ISBN 3-8001-7442-1
Web links
- Tadorna tadornoides inthe IUCN Red List of Threatened Species 2013.1. Listed by: BirdLife International, 2012. Retrieved October 13, 2013.