Settlers introduced invasive species, such as pigs, cats, foxes, weasels, rats and possums, which eat the eggs of ground-nesting birds, and additional declines have been caused by hunting for food, killing as agricultural pests, habitat loss, and introduced wasps.

[19][20] Traditionally, the species of the family Strigopoidea were placed in the superfamily Psittacoidea, but several studies confirmed the unique placement of this group at the base of the parrot tree.

[17] In the Pliocene, supposedly around five million years ago, the formation of the Southern Alps / Kā Tiritiri o te Moana diversified the landscape and provided new opportunities for speciation within the genus Nestor.

[17] The lack of DNA material for the Chatham kākā makes it difficult to establish precisely when those speciation events occurred.

[17] Until modern times, New Zealand and the surrounding islands were not inhabited by four-legged mammals, an environment that enabled some birds to make nests on the ground and others to be flightless without fear of predation.

The genus Nelepsittacus consists of three described and one undescribed species recovered from early Miocene deposits in Otago.

[33] (In modern orthography of the Māori language, the long versions of the vowels a and o are written with macrons; i.e., ā and ō.

The main predators were birds: harriers, falcons, owls, and the massive, extinct Haast's eagle.

The kea is well adapted to life at high altitudes, and they are regularly observed in the snow at ski resorts.

[39] Māori like to refer to the kākā in the tauparapara, the incantation to begin their mihi (tribute), because their voice (reo) is continuous.

The Chatham kākā became extinct between 1500 and 1650 in pre-European times, after Polynesians arrived at the island, and is only known from subfossil bones.

Only a few bat species and sea mammals were present prior to colonisation by humans, and the only predators were birds of prey that hunt by sight.

These circumstances influence the design of New Zealand's parrots, for example, the flightlessness of the kākāpō and the ground breeding of the kea.

[39] The large-scale clearance of forests and bush destroyed its habitat while introduced predators such as rats, cats, and stoats found the flightless, ground-nesting birds easy prey.

Another threat comes from competition with introduced species for food, for example with possums for the endemic mistletoe and rata and with wasps for shimmering honeydew, an excretion of scale insects.