Kagu 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 it has only one-third as many red blood cells and three times more hemoglobin per red blood cell than is usual in birds. 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"
Kagu areas where soil levels of heavy metals were low laid more eggs and had higher numbers of fledglings, as well as having smaller home-ranges and higher body mass, than Kagu in areas where the soil was heavy-metal rich. It has therefor been suggested that Kagu conservation is likely to be more effective in areas where heavy-metal levels in the soil are low. The kagu had an important role in the traditional lives of the Kanak tribes of New Caledonia. Among the tribes found in the vicinity of Hienghène in the north of Grande Terre, its name was given to people,