Ragduck
| Ragduck | ||||||||||
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Ragduck (male) |
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| Systematics | ||||||||||
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| Scientific name of the genus | ||||||||||
| Biziura | ||||||||||
| Stephens , 1824 | ||||||||||
| Scientific name of the species | ||||||||||
| Biziura lobata | ||||||||||
| ( Shaw , 1796) | ||||||||||
The musk duck ( Biziura lobata ) is a species of bird in the family of ducks (Anatidae) whose taxonomic present arrangement is not clear within the family and is discussed. Rag ducks are found exclusively in Australia. They have a very low population density, since the males claim very large breeding grounds.
The IUCN classifies the Ragduck as not endangered ( least concern ). The population is estimated at 20,000 to 50,000 sexually mature individuals.
Appearance
Ragducks show a pronounced sexual dimorphism . The coloring of the sexes is the same, but males are with a body length of about 66 cm and a weight between 1.8 and 3.1 kg significantly larger and heavier than the females, the maximum body length of 55 cm and a weight of 1.0 to Reach 1.9 kg. The wing length of the males is 20.5 to 24 centimeters, that of the females only 16.5 to 20.2 centimeters.
The eponymous black wattles can be used as a clear feature to determine gender. This rounded skin flap below the beak extends to the breast in the males, in the females it is only rudimentary. The wattles are particularly large with increasing age of the males and during the breeding season and recede somewhat during the rest and moulting periods. In the female, however, the throat pouch is only hinted at. The brown-gray plumage marked with light, narrow bands is worn by both sexes. Rag ducks go through two moulting periods each year, during which both the wing and the control feathers are changed. The breeding moult takes place between April and June, the females go through the rest moult in October, the males on the other hand not until December.
Newly hatched chicks have a dark gray-brown head, an equally colored chest and upper body. The belly, on the other hand, is light brown. The beak is bulky and, like the feet, black-gray. Fledglings resemble adult females, but the lower beak is usually dark yellow instead of gray. Males increase in size over several years, with a more pronounced wattled collar developing in parallel.
Typical behaviors
Rag ducks are skillful and persistent divers who can dive quickly and move the surface of the water little when submerged. When swimming, the body lies deeply submerged in the water, the tail either glides flat on the water surface or is stretched upwards. You can swim fast even with one leg stretched on your back. Rag ducks are rarely on land. Your gait appears clumsy on people. They rarely fly up and need to be tried again. Rapid, flat wing beats are characteristic of rag ducks.
Ragducks are generally not very call-friendly ducks. Usually a whistling from the male is only heard during the breeding season.
distribution and habitat
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The disjoint distribution area of the rag duck comprises two partial areas isolated from one another; one area comprises south-west Australia , the second south-east Australia and Tasmania . Sometimes the eastern population is described as a subspecies, which is largely rejected by experts. During the breeding season, the species is found in largely inaccessible wetlands and marshland with heavy reed vegetation. The preferred breeding biotopes are richly structured stocks of reeds and knotweed with sprinkled small areas of water. Outside the breeding season, the species sometimes lives marine near the coast and in areas of estuaries.
Ragducks that breed in permanent freshwater are obviously resident birds. The breeding birds, which, however, only raise their offspring in temporary bodies of water, move to other bodies of water after the breeding season. Presumably they join the squads of young birds. Flocks of rag ducks are regularly observed from late summer onwards in various types of water, and they then also use bays. The colonization of Lake Eyre by rag ducks indicates very long hikes if the conditions are suitable.
food
The food captured by diving consists mainly of invertebrates , occasionally supplemented by amphibians and small fish. In addition, plant-based food, especially seeds, is consumed in small quantities and on occasion. Occasionally grebes also eat the chicks of other duck species, this is particularly common with chicks of the Australian bog duck, which has a distribution area similar to that of the bladder duck .
Ragducks can dive up to six meters deep. Commonly rag ducks stay underwater for 25 to 30 seconds, with a maximum dive time of 60 seconds. Rag ducks only emerge for a few seconds before diving again. They also take food from the surface of the water and peck at vegetation hanging above the surface of the water. They usually only look for food during the day.
Reproduction
Depending on the water level, the breeding season of the species can shift, but as a rule breeding takes place in September and October. The males sometimes quite aggressively defend a courtship area against other conspecifics and mate with several females who raise the young birds alone. The details of reproductive behavior have not yet been adequately investigated, most of the knowledge has been gained from birds kept in human care.
The nest, in which an average of 3 to 4 eggs are laid, consists primarily of dry blades of grass and branches and is set up in dense vegetation. The nesting mat is often so thin and flat that the eggs lie in the moist area. The young birds are raised exclusively by the female. The fledglings keep quiet when the female parent is absent to look for food. But they beg loudly for food when the female appears at the nest. Alarm calls with which the female warns the cubs about predators are not known. The female occasionally carries the juveniles on her back, and observations indicate that the juveniles remain on their backs even during dives. It is not yet known how long the female and fledglings stay together in the wild. However, females have already been caught with young birds weighing just under 1.5 kilograms. The females feed the young birds, which is relatively unusual behavior for ducks. The females dive for food and when it appears again, the young birds rush to her with loud begging sounds. The neck is lowered and the beak is directed upwards.
Ragduck and human
The rag duck is usually not considered tasty and is therefore rarely shot. However, it occasionally gets caught in fishing nets.
Individual rag ducks were shown repeatedly in Europe as early as the 19th century. For example, the London Zoo owned a specimen and, after the turn of the century, the Berlin Zoo too. The ducks were generally aggressive towards roommates. The drake, which was kept in Berlin, repeatedly attacked the other pond inhabitants from below while diving. A couple kept in a French zoo also killed smaller ducks and even ate ducklings. Rag ducks are bred regularly in Australian zoos.
supporting documents
literature
- PJ Higgins (Ed.): Handbook of Australian, New Zealand & Antarctic Birds , Volume 1, Ratites to Ducks, Oxford University Press, Oxford 1990, ISBN 0195530683
- Josep del Hoyo , Andrew Elliot, Jordi Sargatal : Handbook of the birds of the world. Volume 1: Ostrich to Ducks. Lynx Edicions, Barcelona 1992, ISBN 84-87334-10-5 .
- Hartmut Kolbe: The world's ducks. Ulmer Verlag 1999, ISBN 3-8001-7442-1
- Ken Simpson, Nicolas Day, Peter Trusler: Field Guide to the Birds of Australia . - A & C Black, 2004. ISBN 0-7136-6982-9
Web links
- Videos, photos and sound recordings of Biziura lobata in the Internet Bird Collection
- Biziura lobata inthe IUCN 2013 Red List of Threatened Species . 2 . Listed by: BirdLife International, 2012. Retrieved February 5, 2014.