Bush stone-curlew

Appearance

A species of ''Burhinus'', a genus of large-eyed and long-legged terrestrial foragers known as thick-knees, it is slender in form and a grey and brown colour with distinctive markings. The bird has conspicuous dark streaks over the buff and greyish white feathers of the upperparts and spotted markings on the wings. The plumage at lower side of the bird is also strongly streaked with dark brown over white and buff feathers.
The total length of the species, including a bill around 45 mm and tail 180 mm, is 550 mm; the wingspan approaches 1 m across.

Black flight feathers on the wing reveal a light buff patch when extended, and the plumage has a light area at the shoulder.

The head is distinguished by a band of dark feathers over the eye and down the neck, and a buff colour at the forehead and brow over the eye. The iris is bright yellow; bare skin near the eye is black. The long legs of the species are an olive-green colour, and the bill is darkish in tone.

The sexes are similar, with juveniles displaying a paler plumage that otherwise resembles the adults.

No other Australian bird resembles the bush curlew. Another species of the family, the beach stone-curlew also known as a wee-lo, is distinguished by its plumage and larger bill and is only found at the coast. Confusion with the nightjars is possible, but the species of ''Caprimulgus'' are smaller and fly in a different manner.

Status

The assessment noted in the IUCN Red List is not threatened, revising an earlier listing of near threatened with extinction. The population is declining and estimated at 10,000 to 15,000 individuals in 2016. Historical declines recorded during colonisation of Australia are thought to have abated in the 32 years prior to the IUCN's 2016 assessment.

Behavior

This stone-curlew's voice is loud and can be heard at a great distance. The call of "weeloo" has an eerie and plaintive tone and is a familiar sound of the night in the Australian bush. The frequency of calls increases when weather conditions are changing, especially when rain is approaching an area. Several individuals may join their voices in chorus, greatly intensifying the extraordinary quality of their nocturnal calling.



During the day, bush stone-curlews tend to remain inactive, sheltering amongst tall grass or the shade of shrubs and trees, relying on their cryptic plumage to protect them from predators. When disturbed, they freeze motionless, often in odd-looking postures. For visual predators such as raptors and humans, this works well, but it serves little purpose with animals that hunt by scent such as foxes, dingoes, or goannas.

Approaching the camouflaged individual does not dissuade it from this behaviour, maintaining the rigid posture even if handled. If moving from a disturbance, they crouch and walk stealthily into vegetation, only attempting to fly if vigorously pursued.

Despite their ungainly appearance and habit of freezing motionless, they are sure-footed, fast, and agile on the ground, and although they seldom fly during daylight hours, they are far from clumsy in the air; flight is rapid and direct on long, broad wings.

The bush curlew is sometimes recorded in flocks, but when the breeding season occurs, the number of birds in a locality is the usually just a mating pair. Like other ground-nesting birds, the females only select a site to lay the eggs and provide no other adornment to the nest; care of the site is performed by both parents. The brooding parent discreetly moves from the site if disturbed in the first few days of incubation, but remains to defend an egg at a later stage of development. The parent adopts its frozen posture and lays over the eggs in an attempt to hide them. An egg that has been discovered by an intruder may be moved a short distance away.

Habitat

The bush stone-curlew has a broad habitat preference, but is rarely seen in rainforest, arid desert, or urban or agricultural regions. The species is found in open forest, eucalyptus woodland, rainforest edges, grassy plains, arid scrubland, and along inland watercourses.

Food

Like most stone-curlews, it is mainly nocturnal and specialises in hunting small grassland animals; frogs, spiders, insects, molluscs, crustaceans, snakes, lizards, and small mammals are all taken, mostly gleaned or probed from soft soil or rotting wood; also. a few seeds or tubers are consumed, particularly in drought years. Birds usually forage individually or in pairs over a large home range, particularly on moonlit nights.