The bush stone-curlew or bush thick-knee (Burhinus grallarius, obsolete name Burhinus magnirostris ) is a large, ground-dwelling bird endemic to Australia. Its favoured habitat is open plains and woodlands, where it stalks slowly at night in search of invertebrates such as insects. Its grey-brown coloration is distinguished by dark streaks, its eyes are large and legs are long. It is capable of flight, but relies on the camouflage of its plumage to evade detection during the day; the bush curlew adopts a rigid posture when it becomes aware of an observer. Both sexes care for two eggs laid on the bare ground, usually sited near bush in a shaded position or next to a fallen branch.
The Bush stone-curlew is an unusual looking bird, unlike any other Australian bird. It is mainly nocturnal, a large, slim, ground-dwelling bird with long gangly legs, big yellow eyes, and gray streaked upper parts. This coloring makes it hard to see in the bushland, especially in the shadows and in the evening, when most active. Both genders are similar. This charismatic bird has a distinctive, wailing call, described as ‘melancholy’, ‘mournful’, ‘eerie’ or ‘frightening’.
The Bush stone-curlew inhabits all of Australia except for Tasmania and the West Australian coast. Small populations also occur in Indonesia and Papua New Guinea. It lives in a broad range of habitats, from open forest and eucalyptus woodland to rainforest edges, arid scrubland, grassy plains, and along swamps and inland watercourses.
This shy species occupies a breeding territory of 10-25 hectares, living in loose flocks or pairs. During the day it hides, coming out at night to feed on seeds, insects, spiders, small frogs and reptiles. During the breeding season, birds that are nesting will search in the vicinity of their nest site for food, while at other times, they may travel large distances. They always feed from the ground. They squat on the grass during the daytime, either in a small group or alone. When threatened, they stay still or slowly walk away.
Bush stone-curlews are a monogamous species and are thought to maintain long-term pair bonds. They have a remarkable courtship display where an individual will stand with its wings outstretched, its tail upright and its neck stretched slightly forward. It stamps it feet like a soldier who is marking time. This ritual lasts an hour or more and is accompanied by constant loud calling. This species breeds during July and January. The nest is a small clearing or scrape on bare ground, most often near a fallen branch or bush. Two eggs are usually laid, and incubated for 28 days. The incubation and care of the young is shared by both parents, with feeding of the chicks for 4 weeks after hatching. Chicks stay with their parents for 3 to 9 months. The young from the previous clutch are chased away before the next clutch is laid.
The main threats to this species are modification and loss of their habitat for urban development and agriculture, as well as predation by foxes and feral cats. The collection of fallen timber for firewood is a particular concern because this is likely to affect the curlews’ camouflage strategy for avoiding predators.
According to the IUCN Red List, the total Bush stone-curlew population size is 10,000-15,000 mature individuals. Currently this species is classified as Least Concern (LC), but its numbers today are decreasing.