Kiwi are flightless birds endemic to New Zealand of the order Apterygiformes. The five extant species fall into the family Apterygidae (/ˌæptəˈrɪdʒədiː/) and genus Apteryx (/ˈæptərɪks/). Approximately the size of a domestic chicken, kiwi are the smallest ratites (which also include ostriches, emus, rheas, cassowaries and the extinct elephant birds and moa).
DNA sequence comparisons have yielded the conclusion that kiwi are much more closely related to the extinct Malagasy elephant birds than to the moa with which they shared New Zealand. There are five recognised species, four of which are currently listed as vulnerable, and one of which is near threatened. All species have been negatively affected by historic deforestation, but their remaining habitat is well protected in large forest reserves and national parks. At present, the greatest threat to their survival is predation by invasive mammalian predators.
The vestigial wings are so small as to be invisible under their bristly, hair-like, two-branched feathers. Kiwi eggs are one of the largest in proportion to body size (up to 20% of the female's weight) of any order of bird in the world.Other unique adaptations of kiwi, such as short and stout legs and using their nostrils at the end of their long beak to detect prey before they see it, have helped the bird to become internationally well known.
The kiwi is recognised as an icon of New Zealand, and the association is so strong that the term Kiwi is used internationally as the colloquial demonym for New Zealanders.
The Māori language word kiwi is generally accepted to be "of imitative origin" from the call. However, some linguists derive the word from Proto-Nuclear Polynesian *kiwi, which refers to Numenius tahitiensis, the bristle-thighed curlew, a migratory bird that winters in the tropical Pacific islands. With its long decurved bill and brown body, the curlew resembles the kiwi. So when the first Polynesian settlers arrived, they may have applied the word kiwi to the newfound bird. The bird's name is spelled with a lower-case k and, being a word of Māori origin, normally stays as kiwi when pluralised