White-winged Chough

BIRD: linking the biodiversity community

Category: Birds

The White-winged Chough (Corcorax melanorhamphos) is one of just two surviving members of the family Corcoracidae, the Australian mud-nest builders, and the only member of the genus Corcorax.

Choughs are easily recognised but often mistaken for "crows" — a double mistake, as the birds most frequently called crows in southern Australia are actually ravens.

Choughs are large, black birds — at about 45 cm only a little smaller than a raven or a little larger than a Magpie — but have red eyes and a finer, slightly down-curved beak. In flight, the large white eye-patches in the wings are immediately obvious.

They were once common through the drier woodlands and open forests of south-eastern Australia, from near the South Australia - Western Australia border as far north as Townsville. Although still common in patches where good habitat survives, Choughs are weak flyers and do not cope well with habitat fragmentation, so many surviving populations are isolated and thus vulnerable.

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.

The cooperation is not always as it seems, however: young Choughs have been recorded "cheating" — taking food back to the nest and going through the motions of feeding the nestlings, but swallowing it themselves. Interestingly, they seem to do this only when food is in short supply and when adult birds are unlikely to detect the deception. Further, the "cheat" tends to compensate by performing more than the usual amount of allopreening.

The nest itself is a very large bowl made of mud and reinforced with a little grass or plant material; it is usually constructed on a horizontal branch and may be repaired and reused for several years. (Note the similarity with the related Apostlebird and the unrelated Magpie-lark.)

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.

White-winged Choughs can often be seen on the fringes of urban areas if natural bush survives nearby. They can become quite tame and will venture into gardens regularly if conditions are suitable: they need trees for shelter nearby, leaf-litter to search for food in, and protection from domestic pets.

[edit] See also:

• Apostlebird
• Corcoracidae
• Boland, Heinsohn & Cockburn, Deception by helpers in cooperatively breeding white-winged choughs and its experimental manipulation. Behavioral Ecology and Sociobiology, 41, 251-256.