Australian Ferruginous Duck(Aytha australis)
The Australian Ferruginous Duck(Aythya australis) is the only diving duck in Australia. It is found throughout the Australian continent. However, it is rarely seen on Tasmania. Its plumage colouring is reminiscent of the European Ferruginous Duck. However, it is slightly larger and the plumage is less uniformly brown.
The IUCN classifies the Australian Ferruginous Duck as not endangered(least concern). The population is estimated to range from 100,000 to 1 million sexually mature individuals. In Australia, this species is considered a game bird.
Appearance of adult Australian Ferruginous Ducks
Relative to other ducks, Australian moor ducks are very small birds. They usually have a body length of about 45 centimetres. However, there is a wide variation in body size, ranging from 42 to 59 centimetres. The wingspan is 65 to 70 centimeters. The weight varies from 800 to 900 grams. In body shape, they are strikingly roundish. Australian moor ducks are not characterized by a pronounced sexual dimorphism. However, the sexes can be distinguished by eye color. In the male, the iris is white, while the female has a brown iris. In flight, the Australian Ferruginous Duck can be easily distinguished from other ducks by the white underside of its wings and its pale belly.
In the splendour dress the male has a bright reddish-brown plumage. On the head and breast the plumage is almost glossy. The flanks, back and tail are a slightly darker reddish brown. The underparts of the tail are white and the underparts are also white. The wing side is white with a narrow brown border. The bill is dark gray with a conspicuous gray-blue band just before the nail. The resting dress is the same as the female. This is very similar to the male, but has a duller overall plumage coloration. The bill coloration is the same as the male, but slightly less conspicuous overall.
Australian moor ducks undergo a full moult as soon as breeding is complete.
Appearance of chicks and young birds
Australian moorhens that are not yet adults have plumage similar to the female. However, they are somewhat paler overall. This overall paler plumage is particularly noticeable on the chin and throat. The iris is still hazel brown. The bill is still dark lead-grey throughout. The formation of the light beak band begins in the 5th to 6th month. On the underside of the body they are more strongly spotted. A reliable differentiation between young birds and adult females is only possible in the hand, i.e. if they can be captured for ringing, for example, and their feathers and weight measured.
The chicks are dark brown on the upper side of the body. The face is light straw-yellow and has no conspicuous color spots. There are broad yellow stripes on the wings. There are two pale yellow spots on the rump.
Distribution, habitat and population
The Australian Ferruginous Duck has a range that is usually restricted to Australia and Tasmania. However, it is not excluded that the Australian Ferruginous Duck was a regular breeding bird there prior to European settlement in New Zealand. It is characteristic of Australian Ferruginous Ducks that migratory Ferruginous Ducks colonise floodplains for short periods and leave them just as quickly when they dry out. In years when abundant rainfall causes a high population increase, a very widespread dispersal occurs. Australian moor ducks then also migrate over long distances, occasionally reaching New Guinea, New Zealand and other Pacific islands. They occasionally breed there as well. However, long-term settlement has not yet occurred after such colonizations. On New Zealand the Australian Ferruginous Duck was common when first observed by Europeans. The Māori have a name for this bird species, which also indicates that it was once more common in New Zealand.
For habitat, Australian moor ducks inhabit wetlands with deep waters whose bottoms provide a rich food supply. They are rare in salt marshes, but occasionally find themselves in freshwater lagoons in coastal areas, colonizing salt lakes, mangrove swamps and brackish water. They are seldom seen on land and never rear.
Population numbers of the Australian Ferruginous Duck are difficult to determine. Population figures for the entire continent are lacking. However, between 1983 and 1992 aerial surveys were used to determine population size for a large area in eastern Australia. In this area an average population of 170,000 individuals was determined. At its peak, up to 620,000 individuals were counted. Basically, it is assumed that the population numbers fluctuate strongly and, similar to the Monkey Duck, are large after periods with abundant rainfall.
Food and foraging
Like other diving ducks, they forage during dives and then occasionally stay underwater for up to a minute. They are such skilled divers that they barely cause ripples on the surface of the water when they dive in. Underwater, they move around with the help of their large feet. They find their food by searching the bottom with their beaks. Besides this, burrowing and straining also takes place. Australian moor ducks feed mainly on small aquatic organisms and only occasionally eat aquatic plants. Foraging on grassland and other agricultural areas is very rare.
No detailed studies of the reproductive behaviour of the Australian Ferruginous Duck are available to date. The Australian Ferruginous Duck seems to be a solitary breeder, which builds the nest in the immediate vicinity of the water in dense vegetation. The nests are compact structures with a deep nest depression and often an arbour-like roof.
The Australian breeding season is not exactly fixed, but seems to fall in the period August to December. However, there is sufficient evidence that an intense breeding season occurs after large rainfalls, when much land in inland Australia is flooded. In northeastern New South Wales, broods are regularly observed in January and February, but further inland in New South Wales they occur mainly in the period September to December.
It is the female alone that broods, and she alone leads the chicks. The eggs are elliptical. The shell is shiny and creamy white. The eggs are the largest yet recorded in white-eyed ducks. They average 57 × 42 millimeters in size. According to present knowledge, a full clutch comprises nine to thirteen eggs. Larger clutches are due to several females laying in one clutch. Maned Geese also occasionally lay their eggs in the nests of Australian Moor Ducks. The incubation period has not been adequately studied in the wild, but is believed to be 25 days. Chicks raised in human care weigh 29.5 grams after hatching.
Attitude in Europe
The Australian Ferruginous Duck was imported to Europe very late. The first European keeper was probably the British Wildfowl Trust, which received 3 pairs from Australia in 1959 and thus established a breeding program. The European zoo population was founded from the offspring. From 1966, for example, the Tierpark Berlin kept Australian Moor Ducks. As Australian Moor Ducks have a less spectacular plumage and a great resemblance to European Moor Ducks, they never became a popular ornamental fowl. Their population in European zoos is also small to this day. Despite their subtropical home, Australian Moor Ducks are considered to have little sensitivity to cold and are kept like European Moor Ducks.
- P. J. Higgins (ed.): Handbook of Australian, New Zealand & Antarctic Birds. Volume 1, Ratites to Ducks, Oxford University Press, Oxford 1990, ISBN 0195530683.
- Janet Kear (ed.): Ducks, Geese and Swans. Oxford University Press, 2005, ISBN 0198546459.
- Hartmut Kolbe; Die Entenvögel der Welt. Ulmer Verlag 1999, ISBN 3-8001-7442-1.
– Collection of images, videos and audio files
- BirdLife Factsheet on the Australian Ferruginous Duck
- Aythya australis in the IUCN Red List of Threatened Species 2013.2. Submitted by: BirdLife International, 2012. retrieved 23 November 2013.
- Kolbe, p. 279
- BirdLife Factsheet on the Australian Ferruginous Duck, accessed 22 April 2011
- Higgins, p. 1353
- Kear, p. 655
- Higgins, p. 1351
- Kolbe, p. 280
- Higgins, p. 1352
- Kear, p. 636
- Kolbe, p. 280
- Kear, p. 656
- Higgins, p. 1355
- Kear, p. 657