This is one of these forms that can be interpreted either as a subspecies or as a full species in its own right. In this particular case interpretation is a subjective commodity and each of the interpretations has its merits. The Kaka (Nestor meridionalis) is a relatively well-known representative of the New Zealand avifauna, widely distributed, although nowhere plentiful, on both main islands and on a number of smaller offshore islands. It is a fairly stocky parrot of medium size with striking but quite variable plumage. Until around the middle of the nineteenth century a closely related bird occurred on Norfolk Island and its close neighbour Phillip Island, both of which lie in the Tasman Sea almost half way between New Zealand and Australia.
The plumage of the Norfolk and Phillip Island birds is somewhat different to those from New Zealand, but it seems quite likely that the two could have interbred, had they come into contact. However, the two forms have acquired a fairly separate identity in ornithological literature and if museum specimens are compared it is quite easy to tell them apart – even without reference to locality data. All birds on Norfolk Island were badly affected by the establishment of penal settlements for criminals transported from Britain. These were founded during the last decade or so of the eighteenth century and they were used during the first few decades of the nineteenth. There is no doubt that convicts and early settlers entirely disrupted the peace and tranquility of the island and the large, brightly coloured parrots would have made a very tempting target.
Norfolk Kakas were probably caught primarily for food but there is no doubt that they were also taken as pets. The famous ornithological writer John Gould saw one in Sydney during his visit in the late 1830’s and the last individual of all may well have been a bird that died in its cage in London in 1851, or soon after. Almost nothing is known of the bird in the wild. Apparently it nested in holes in trees and laid up to four eggs. It frequented the rocks and the tree tops, was very tame, as might be expected in an island form, and was seen feeding on blossoms. The population seems to have been prone to a strange deformity of the beak. As far as is known these parrots were first extirpated on Norfolk Island, and held out for a little longer on Phillip.
Proc. Zool. Soc. London 1836: 19.