Australian bittern
| Australian bittern | ||||||||||||
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Australian bittern ( Botaurus poiciloptilus ) |
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| Botaurus poiciloptilus | ||||||||||||
| ( Wagler , 1827) |
The Australian bittern ( Botaurus poiciloptilus ) is a species from the subfamily of the bittern . It occurs exclusively in Australia, New Zealand and some neighboring islands. The species is closely related to the Eurasian bittern . The dull courtship call of the Australian bittern is also similar to that of the bittern. The world population is very small and is estimated to be less than 2500 birds. The IUCN lists this species as endangered .
Appearance
Australian bitterns reach a height of 66 to 76 centimeters. The females weigh between 571 and 1135 grams; the weight of the males varies between 875 and 2085 grams. The difference in size between the sexes can also be seen in field observations.
Australian bitterns have a body shape characteristic of a bittern. They are built relatively compact, the neck is very thick and the plumage is speckled brownish. The top of the head is brown. The beak is yellow to yellow-brownish and the middle of the upper bill is dark brown to gray-black. The iris is yellow. A creamy white fine line runs above the eye. The sides of the face are yellow-brown. From the beak on each side of the face a very dark stripe runs down the neck. The rear neck and the back are dark brown with yellow-brown longitudinal stripes and a spot, which gives the dommel an overall strongly spotted and striped appearance. The wing covers have a very fine brown and yellow-brown stripe pattern. The chin and upper throat are white. The chest is white with large brown longitudinal spots. The belly is white. The lower wing covers are yellowish brown with brown speckles. The legs and feet are green-yellow to olive-colored.
The flight is cumbersome. Startled Australian bitterns fly only short distances and then fall into the nearest cover. The flapping of the wings is very even over longer distances. The flight is described as being owl-like.
There are possibilities of confusion in the distribution area with not yet fully colored red-backed herons and black bittern . The Australian bittern, however, is significantly larger than these two species.
Distribution area, population and habitat
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The Australian bittern is only found in the southeast and southwest of Australia. It also breeds in the Bass Strait Islands , Tasmania and New Zealand, and New Caledonia . The species is basically a resident bird. There may be a few walking movements depending on the rainy and dry seasons.
In western Australia there are only about 100 breeding pairs. Due to the intensive agricultural use, which went hand in hand with extensive drainage, there are only a few suitable habitats left. These can only be found in the rainy areas along the west coast. In the Australian states of New South Wales and Victoria, the Australian bittern is still relatively common in the catchment area of the Murray River and its main tributary, the Darling River . In 1985, the New Zealand population consisted of only 580 to 725 Australian bitterns.
The habitat of the Australian bittern is freshwater with a dense belt of reeds in shallow water zones with a depth of less than 30 centimeters. The species mostly leads a very hidden life and can only rarely be seen outside of this reed area.
Way of life
Australian bitterns are mostly solitary. Very rarely they can be seen in pairs or in small groups of up to twelve birds. He looks for his food mainly at night and in the twilight. During the winter months, the Australian bittern can occasionally be seen during the day. While foraging for food, the Australian bittern moves very slowly in a crouched position. If she feels worried, she takes the pole position that is characteristic of dommels. The diet consists of fish, frogs and crustaceans as well as insects, spiders, clams, lizards, rats, mice and small birds.
The breeding season falls from October to February. The nest is built in the reed belt and Australian bitterns usually breed solitary. However, up to seven nests have been found in closer proximity to each other. The clutch consists of four to five eggs. The brood begins with the laying of the first egg, the incubation period is 25 days. The female breeds alone. The young birds can fledge at around seven weeks.
supporting documents
Single receipts
- ↑ BirdLife Factsheet , accessed September 13, 2009
- ↑ Kushlan et al., P. 302
- ^ Higgins, p. 1057
- ^ Higgins, p. 1058
- ↑ Kushlan et al., P. 304
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
- James A. Kushlan & James A. Hancock: Herons . Oxford University Press, 2005, ISBN 0-19-854981-4
Web links
- Botaurus poiciloptilus in the Red List of Threatened Species of the IUCN 2013.1. Listed by: BirdLife International, 2012. Retrieved November 21, 2013.