Le Kagou huppé ou simplement Cagou (Rhynochetos jubatus) est une espèce d'oiseau qui mesure environ 55 cm, de couleur grisâtre, aux longues plumes occipitales, au plumage blanchâtre orné de barres sur les ailes. Il est presque incapable de voler. C'est le seul représentant de la famille des Rhynochetidae et du genre Rhynochetos endémique de Nouvelle-Calédonie.

Description
Il possède un plumage gris-bleu rayé de noir, un bec et des pattes rouges, ainsi qu'une coiffe qui lorsqu'elle se dresse nous montre un panache de chef indien. Il mesure environ 60 cm.

Comportement
Il vit entièrement au sol, que ce soit pour la chasse ou pour la reproduction et ne vole pas. C'est une faiblesse pour lui. Ses principaux prédateurs sont l'Homme, les chiens et les chats sauvages, les cochons, et les rats. C'est l'absence de prédateurs avant l'arrivée de l'Homme qui aurait conduit à la « perte du vol ». Cela lui procurait une économie d'énergie importante. En 1991, sa population était estimée à 654 individus. Le cagou est donc une espèce extrêmement menacée. Lorsqu'il se sent menacé il court rapidement et se cache. Il peut également ouvrir ses ailes en éventail et dresser sa huppe sur sa tête s'il ne peut pas fuir car il a un poussin avec lui. Les cagous poussent un cri matin et soir. Ce cri ressemble à un aboiement de chien disant « kagu ». C'est ce qui lui a valu ce nom-là par les autochtones. Vivant en couple, un couple de cagou est établi pour la vie et vit sur un territoire variant de 5 à 30 hectares. Il se nourrit surtout de ver de terre, mais mange aussi quelques lézards et escargots. Chaque matin le couple chante afin de signaler sa présence. Le chant du mâle se compose de douze syllabes alors que celui de la femelle est plus court, environ sept syllabes. Il passe le reste de la journée à la quête de nourriture. Il est principalement carnivore et se nourrit principalement d'insectes, de larves et d'escargots. Il possède une excellente vision. Il reste immobile, dressé sur une patte à l'affût du moindre bruit. Il est doté d'une rapidité impressionnante pour capturer ses proies. Il utilise parfois son bec pour fouiller des couches de feuilles mortes afin de trouver de la nourriture. Lorsque la nuit tombe, il s'installe dans un abri naturel.

Habitat
Son biotope est constitué de forêts denses et humides mais aussi de zones broussailleuses, toutes situées entre 100 et 1 400 mètres d'altitude.

Répartition
Il vit exclusivement en Nouvelle-Calédonie, c'est donc une espèce endémique.

Reproduction
Il n'y a pas de dimorphisme sexuel chez le cagou. Seuls leurs chants ou une analyse génétique permettent de déterminer mâles et femelles. La maturité sexuelle du cagou est encore floue, elle est généralement atteinte l'âge de deux ans. Le cycle de reproduction débute en juin, pendant la saison fraîche. Il commence généralement par une parade nuptiale: le mâle et la femelle sont face à face, ailes ouvertes, huppes dressées et tournent l'un autour de l'autre. Répétée plusieurs fois, cette danse peut être suivie d'accouplements successifs. Environ trois semaines après, le couple cherche un endroit paisible pour accueillir la progéniture. Le nid est construit à même le sol, constitué de branches sèches et de feuilles mortes, il mesure environ 35 cm de diamètre. La femelle ne pond qu'un seul œuf par an. Il est marron crème tacheté de rouge brun. Cet œuf mesure 60 mm de long et pèse 52 g. L'incubation dure environ 35 jours, le mâle et la femelle se relaient chaque jour, vers midi. À la naissance, le poussin est couvert d'un léger duvet de couleur brun jaune qui rappelle le sol. Cela lui permet de mieux se camoufler. Au bout d'une semaine le poussin commence à s'aventurer à une centaine de mètres du nid. Depuis la naissance et jusqu'à la 15e semaine, le jeune poussin sera nourri par ses parents. Ils tiennent la proie (vers de terre et insectes essentiellement) dans leur bec pour que le jeune l'ingurgite. À partir de la quinzième semaine il est apte à se nourrir seul. Son plumage ne cesse d'évoluer depuis sa naissance. Ce n'est que vers deux ans que son plumage roux de jeune cagou cède sa place au gris bleuté de l'adulte. À partir de là, le jeune cagou quitte le territoire de ses parents pour former à son tour un couple sur un nouveau territoire.

Protection et réintroduction
Le cagou est entièrement protégé. Il ne peut en aucun cas être commercialisé. Sa capture et sa détention sont strictement interdites. Il voit déjà son territoire empiété par les activités humaines, en effet les pistes de terre et les plates-formes peuvent constituer une barrière infranchissable pour le cagou, il se retrouve donc isolé et réduit à un seul territoire. Ils sont très vulnérables et c'est pourquoi le parc provincial de la Rivière Bleue dans le sud de la Nouvelle-Calédonie a mis en place un programme de mise en réserve et de gestion du territoire avec une élimination des prédateurs dans les zones les plus propices à sa conservation.

Espèces apparentées
Des ossements ont été découverts par des scientifiques permettant de conclure qu'il y aurait eu une autre espèce de cagou, plus grande que celle actuelle, qui aurait disparu peu de temps après l'arrivée de l'Homme.

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The Kagu or Cagou (Rhynochetos jubatus) is a crested, long-legged, and bluish-grey bird endemic to the dense mountain forests of New Caledonia. It is the only surviving member of the genus Rhynochetos and the family Rhynochetidae, although a second species has been described from the fossil record. Measuring 55 cm (22 in) in length, it has pale grey plumage and bright red legs. Its 'nasal corns' are a unique feature not shared with any other bird. Almost flightless, it a spends its time on or near the ground, where it hunts its invertebrate prey, and builds a nest of sticks on the forest floor. Both parents share incubation of single egg, as well as rearing the chick. It has proved vulnerable to introduced predators, and is threatened with extinction.

Taxonomy and systematics
The Kagu's affinities are not too well resolved. It was long one of the most enigmatic birds and in more recent times usually affiliated with the Gruiformes. It was initially classed as a member of the clade Ardeidae because of the presence of powder down, similarities in plumage coloration and internal anatomy, the coloration of the chicks and eggs, an the change in the coloration as it grows. 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. Recent studies do indicate that the Sunbittern is the closest living relative of the Kagu. For example, Fain & Houde found these to be certainly sister taxa. 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, Caprimulgiformes, flamingos, tropicbirds, Apodiformes, sandgrouse and grebes. The internal structure of this group was not well resolvable by their data, and contains numerous groupings which are almost certainly incorrect (such as Caprimulgidae and flamingos). Thus, the entire "Metaves" may be nothing more than a collection of lineages united by molecular homoplasies. Nonwithstanding, the Kagu and Sunbittern, and possibly the adzebills, seem to form a distinct Gondwanan lineage of birds, possibly one order, possibly more, even though the relationships between them, the mesites, and the "core Gruiformes" are not yet resolved. It is notable, however, that the Sunbittern and the mesites possess powder down too, whereas the "core Gruiformes" do not. While the Kagu is the only living species in the clade Rhynochetidae, a larger species, the Lowland Kagu (Rhynochetos orarius), has been described from Holocene subfossil remains. The measurements of this species were 15% bigger than Rhynochetos jubatus, with no overlap in measurements except those of the forelimbs. Given that the sites where Rhynochetos orarius were all lowland sites, and that no fossils of Rhynochetos jubatus were found in these sites, the scientists that described the fossils suggested they represented highland and lowland species respectively. Rhynochetos orarius is one of many species to have become extinct in New Caledonia after the arrival of humans. The validity of the species has been questioned by some authors, but accepted by others.

Etymology
The generic name, Rhynochetos, and the clade name Rhynochetidae, are derived from the Greek rhis meaning nose and chetos meaning corn, referring to the corn-shaped flaps over the nostrils. The specific name jubatus is derived from the Latin iabatus meaning crested. The name kagu is derived from the Melanesian names for the species. 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).

Description
The Kagu is a ground-living bird, 55 cm (22 in) in length. The weight can vary considerably by individual and by season, ranging from 700–1,100 g (25–39 oz). Its plumage is unusually bright for a bird of the forest floor; ash-grey and white coloured. There is little sexual dimorphism beyond a difference in the amount of barring in the primary feathers. It possesses powder downs which help keep it dry and insulate it in the extremes of New Caledonia's tropical climate. The crest, which is used to display to other members of the species, is barely noticeable when at rest but can be erected and fanned out. It is nearly flightless, using its wings for displays (its primary wing feathers are patterned), and for moving quickly through the forest. It can also use them to glide when fleeing danger. The wings are not reduced in size like some other flightless birds, and have a span of around 77.5 cm (30.5 in), but they lack the musculature for flight. It possesses bright red legs which are long and strong, enabling the bird to travel long distances on foot and run quickly. 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. It possesses 'nasal corns', structures covering its nostrils, which are a feature not shared by any other bird. These are presumed to prevent particles entering the nostrils when probing in soil during feeding. Another unique characteristic of the species is that has only one-third the red blood cells and three times the hemoglobin per RBC compared to the usual situation in birds. Kagus make a range of different sounds, most commonly duetting in the morning, each duet lasting about 15 minutes.

Distribution and habitat
The Kagu is endemic to the forests and shrubland of New Caledonia. Within that island group it is restricted to the main island of Grande Terre. 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. The Kagu is a habitat generalist and able to exist in a range of different forest types if sufficient prey is present, from rain forest to drier lowland forest. They are also able to feed in some drier shrubland associated with the island's ultrabasic rocks, although not the low prey poor shrubland of this type. They are also absent from areas where extensive ground cover makes foraging difficult, such as grassland or areas with high fern cover, but may pass through such areas to reach other foraging areas. The species has undergone some range contraction due to hunting and predation by introduced species. Its original, pre-human distribution, and the extent to which is 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.

Behaviour and ecology
Kagu are territorial, maintaining year-round territories of around 10-28 hectares (22-62 acres). Within the territory the pairs are solitary during the non-breeding season, and may have separate but overlapping foraging areas. The Kagu's crest and wings are used in territorial displays towards other Kagu, slightly different displays are used towards potential predators. Territorial disputes may be resolved by fighting using wings and bills, in the wild this seldom results in serious injuries

Feeding
The Kagu is exclusively carnivorous, feeding on a variety of animals with annelid worms, snails and lizards being amongst the most important prey items. Also taken are larvae, spiders, centipedes and insects such as grasshoppers, bugs, and beetles. The majority of the diet is obtained from the leaf litter or soil, with other prey items found in vegetation, old logs and rocks. Sometimes Kagus will hunt small animals in shallow water. Their hunting technique is to stand motionless on the ground or from an elevated perch, and silently watch for moving prey. They may stand on one foot and gently move the leaf litter with the other foot in order to flush prey. Having located prey they will move towards the prey and stand over it, ready to strike, or make a dash towards the prey from their watching location. If digging is required to obtain the prey this is done with the bill, the feet are not used to dig or scratch away debris.

Breeding
Kagus are monogamous breeders, generally forming long-term pair bonds that are maintained for many years, even possibly life. Kagu can be long lived, with birds in captivity living for over 20 years. A single nesting attempt is made each year, although should the first nesting attempt fail a second attempt is made that year. 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. The nest is not concealed but is usually adjacent to a tree trunk, log or low vegetation. A single grey slightly blotched egg is laid which weighs 60-75 g. Incubation duties are shared by the parents. Each bird will incubate the egg for 24 hours, with the changeover occurring around noon each day. 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. The incubation period lasts for 33–37 days, which is long for the size of the egg. Offspring may remain in their parents' territory for many years after fledging, sometimes up to six years. These chicks do not help in incubating the eggs or raising the chicks, but nevertheless improve the breeding success of the parents. The older offspring do apparently help in territory defence, responding to playback of rivals and also participating in territorial fights, and it has been suggested that this should be treated as a form of cooperative breeding.

Relationship with humans
The Kagu had a variable role in the lives of the Kanak tribes of New Caledonia. To the tribes found in the vicinity of Hienghène in the north of Grande Terre it plays a role in tribal traditions, with its name being given to people, its crest being used in the head-dresses of chiefs, and its calls being incorporated into war dances. The calls of the Kagu were considered messages to be interpreted by the chiefs. Kanaks in the vicinity of Houaïlou referred to the species as the "ghost of the forest". The species was not discovered by European scientists until the French colonisation of New Caledonia in 1852 and was not described until a specimen was brought to the Colonial Exhibition in Paris in 1860. This led to a surge in scientific interest in the species, which resulted in many birds being trapped for museums and zoos. The species was also trapped for food, and was considered a delicacy by European colonisers. It was also fashionable to own Kagus as pets. A campaign was run between 1977-1982 to phase out the pet trade. Today Kagus are considered very important in New Caledonia; they are a high profile endemic emblem for the Territory. Its distinctive song used to be played to the nation every night as the island's TV station signed off the air. Its survival is considered important for the nation's economy and image.

Status and conservation
Concern was first raised about the future of the Kagu in 1904. It is threatened by the introduced cats, pigs and dogs. The bird was hunted to be sold as pet in Europe. The species was also trapped extensively for museums and zoos prior to being afforded protection. New Caledonia lacked mammals prior to the arrival of humans (except for bats), and many insular species have been negatively impacted by introduced mammals. Rats have a big impact on nestlings, accounting for 55% of nestling losses. The first concrete evidence for the effect of dogs came when a New Zealand researcher's study population was quickly exterminated by dogs in the 1990s, although suspicions about the importance of dogs and other predators had been voiced prior to this and dog control measures had been enacted in some areas in the 1980s. Its initial decline was caused by subsistence hunting, and by capture as pets. They also suffer from habitat loss, caused by mining and forestry. The Kagu is listed as endangered (CITES I), and enjoys full protection in New Caledonia. It has been the subject of highly dedicated conservation efforts, and is receptive to ex-situ conservation, breeding well in Nouméa Zoo. It is also prospering in Rivière Bleue Territorial Park, which has a pest management programme and has been the site of releases into the wild of the captive bred birds.