Vertebrate Zoology - V. M. Konstantinov 2011

Chordates
Terrestrial, or Tetrapod, Vertebrates — Amniotes
Class Birds — Subclass Fan-tailed Birds, or Modern Birds — Superorder Paleognathae, or Ratites — Order Kiwis

Kiwis are the smallest ratites (see Fig. 144), about the size of a large chicken, weighing 2 — 3 kg and standing up to 55 cm tall. Their bodies are compact, featuring a short neck—unlike ostriches—and relatively short, four-toed legs. The bill is exceptionally long and gently curved downward, with nostrils opening near its tip. Their plumage resembles Hair, consisting of long, loose-barbed feathers. The wings are vestigial, and the tail is absent, though a uropygial gland is present. Native to the islands of New Zealand, kiwis lead a nocturnal lifestyle, Setting them apart from other ratites. Ininhabiting forests and dense shrublands, they feed primarily on earthworms, insects, and occasionally plant matter. They locate their food mostly by smell, possessing a far more acute sense of Olfaction than any other bird species.

Kiwis have a very low reproductive rate. The clutch typically contains a single, exceptionally large egg—more rarely two—weighing up to 450 g (about 1/5 of the female's body weight) and measuring 12 — 14 cm in length. Both parents share incubation duties. The incubation period varies significantly, lasting from 42 to 70 days. Chicks hatch fully feathered and measuring 2.5 cm long. They leave the nest six days after hatching and reach sexual maturity between 3 and 5 years of age.

Kiwis have been severely decimated by hunting and introduced predatory mammals in New Zealand. Today, they are under strict total protection. Of the three existing species, the little spotted kiwi (Apteryx oweni) is listed in the IUCN Red List.