White-winged Chough
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| Corcorax melanorhamphos (Vieillot, 1817) |
The White-winged Chough (Corcorax melanorhamphos) is one of only two surviving members of the Australian mud-nest builders family, Corcoracidae, and is the only member of the genus Corcorax. It is native to south-eastern Australia and is an example of convergent evolution as it is only distantly related to the European choughs that closely resembles in shape and was named after.
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[edit] Description
White-winged Choughs are easily recognised but often mistaken for "crows"—a double mistake, as the birds most frequently called "crows" in Australia are actually ravens. (See Australian Raven and Little Raven.) The White-winged Chough is a large, black bird—at about 45 cm only a little smaller than a raven or a little larger than an Australian Magpie—but has red eyes and a finer, slightly down-curved beak, similar to a European Chough. These red eyes become swollen and brighter in colour when the bird is excited. In flight the large white eye-patches in the wings are immediately obvious.
[edit] Behaviour
Choughs are territorial and highly social, living in flocks of from about 4 up to about 20 birds, usually all the offspring of a single pair. Nesting and breeding is communal, all members of the family helping to raise the young - a process that takes several years, as young birds must learn the art of finding food in the dry Australian bush. Larger families have a better chance of breeding success: so much so that given the opportunity choughs will kidnap the youngsters of neighboring families in order to recruit them to the team: the more helpers the better!
All members of a family take turns to incubate, preen, and feed youngsters, and all cooperate in defending the nest against predators. However, the juveniles, who are highly inefficient foragers, sometimes engage in deception: they bring food back to the nest, wait until all adult birds have departed, and then eat it themselves. There are three main threats to young choughs: starvation; predation by nest-robbing birds, particularly currawongs; and sabotage by neighbouring chough families anxious to protect their food supply by restricting competition. Larger family groups are better able to deal with all three threats.
Flight is a mixture of a slow, deep flapping and short glides: unlike their European namesakes, White-winged Choughs are not particularly strong or agile fliers and spend the great majority of their time on the ground, foraging methodically through leaf litter for worms, insects, grain, and snails in a loose group, walking with a distinctive swagger, and calling softly to one another every few seconds. A rich find is the cause of general excitement and all come running in to share in it. The family group walks several kilometers each day through its large territory, foraging as it goes, taking to the air only if disturbed.
[edit] See also
- Apostlebird, Stuthidea cinerea
- The unrelated European Chough (Pyrrhocorax pyrrhocorax), and Alpine Chough (P. graculus).
[edit] Further reading
- Boland, C. R. J., Heinsohn, R., & Cockburn, A. (1997). Deception by helpers in cooperatively breeding white-winged choughs and its experimental manipulation. Behavioral Ecology and Sociobiology, 41, 251-256
[edit] References
- BirdLife International (2004). Corcorax melanorhamphos. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 12 May 2006. Database entry includes justification for why this species is of least concern
[edit] External links
- White-winged Chough videos on the Internet Bird Collection
