Black-backed bittern | |
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Black-backed bittern (adult male) | |
Scientific classification | |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Aves |
Order: | Pelecaniformes |
Family: | Ardeidae |
Genus: | Ixobrychus |
Species: | I. dubius |
Binomial name | |
Ixobrychus dubius Mathews, 1912 |
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Synonyms | |
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The black-backed bittern (Ixobrychus dubius), also known as the black-backed least bittern or Australian little bittern, is a little-known species of heron in the family Ardeidae found in Australia and vagrant to southern New Guinea. Formerly lumped with the little bittern, it is one of the smallest herons in the world.
The bittern has sometimes been regarded as a subspecies of the little bittern (Ixobrychus minutus), or of the New Zealand little bittern (I. novaezelandiae). However, molecular evidence has shown it to be more closely related to the yellow bittern (I. sinensis) than to the African and Palaearctic forms of the little bittern, and it is now recognised as a full species.
This species measures from 25 to 36 cm (9.8 to 14.2 in), has a total weight of 60–120 g (2.1–4.2 oz), averaging 84 g (3.0 oz). This is a very small bittern and one of the smallest herons in the world. The adult male has largely black upperparts, including a black cap, while the underparts, as well as the neck, breast and the sides of the head, are rich chestnut. There are large buff patches on the shoulders, conspicuous in flight. The female is duller, brown and streaked on back and crown; immature birds are similar. The irides are yellow, the bill is yellow with a black culmen, and the feet and legs greenish-yellow.
In Australia the bittern is found in the south-east of the continent, with most records deriving from the Murray-Darling Basin, as well as patchily along the east coast, and in south-west Western Australia where it is locally common on the Swan Coastal Plain. Some scattered records are given from elsewhere, including coastal locations in the Kimberley region, the Top End, and the Torres Strait islands, with vagrants occasionally reaching Lord Howe Island and New Zealand.