The kagu or cagou (Rhynochetos jubatus) is a crested, long-legged, and bluish-grey bird endemic to the dense mountain forests of New Caledonia.

Almost flightless, it spends its time on or near the ground, where it hunts its invertebrate prey, and builds a nest of sticks on the forest floor.

[4] The species is variously known as the kavu or kagou in the Kanak languages, and as the cagou in French (also used as an alternative spelling in English).

[5][page needed] When seen as a gruiform, the kagu is generally considered related to the extinct adzebills from New Zealand and the sunbittern from Central and South America.

[7] They and the mesites did not group with traditional Gruiformes in their study, but instead with their proposed clade Metaves, which also includes the hoatzin, pigeons, nightjars, flamingos, tropicbirds, Apodiformes, sandgrouse, and grebes.

The internal structure of this group was not well resolvable by their data, although later studies confirmed a close relationship between the kagu and sunbittern.

[5][page needed] It possesses powder down which helps keep it dry and insulates it in the extremes of New Caledonia's tropical climate.

[5][page needed][9] These wings are also used for a 'broken-wing' display, a behaviour shared with their relative sunbittern, used to fake an injury and draw the attention of a predator away from their chick.

It has large eyes, positioned so that they give good binocular vision which is helpful in finding prey in the leaf litter and seeing in the gloom of the forest.

There is no evidence that it occurred on the Loyalty Islands, although fossil remains of the extinct lowland form R. orarius have been found on the Ile des Pines.

[5] Its original, pre-human distribution, and the extent to which it and its sister species R. orarius coexisted in lowland areas of New Caledonia, is still not fully understood and awaits further research into the subfossil record.

[9][13] However the social organisation of kagu has been disrupted in recent years due to attacks by dogs and families.

[5][13] The kagu is exclusively carnivorous, feeding on a variety of animals, with annelid worms, snails and lizards being amongst the most important prey items.

The majority of the diet is obtained from the leaf litter or soil, with other prey items found in vegetation, old logs and rocks.

Their hunting technique is to stand motionless on the ground or from an elevated perch, and silently watch for moving prey.

[5] Kagus are monogamous breeders, generally forming long-term pair bonds that are maintained for many years, even possibly life.

[12] A simple nest is constructed, which is little more than a heaped pile of leaves, although in some cases the egg may be laid directly on the ground.

A single grey slightly blotched egg is laid which weighs 60–75 g. Incubation duties are shared by the parents.

During each incubation stint the parent will remain on the egg the whole time except early in the morning, when the bird will briefly move away to call to its mate and occasionally forage quickly.

It is also prospering in Rivière Bleue Territorial Park,[21] which has a pest-management programme and has been the site of releases into the wild of captive-bred birds.

[15] Recent research has shown that naturally occurring heavy metals in the soil may affect Kagu through their food supply.

"[5] The species was not discovered by Europeans until the French colonisation of New Caledonia in 1852 and was not described until a specimen was taken to the Colonial Exhibition in Paris in 1860.