Kagu close relationship between the kagu and sunbittern. The kagu and sunbittern, and possibly the adzebills, seem to form a distinct Gondwanan lineage of birds, possibly one order, possibly more, though the relationships between them and groups previously considered related, such as 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
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,