New Zealand kiwi bird.
Conservation status: Vulnerable
A kiwi is any of the species of small flightless birds native to New Zealand of the genus Apteryx (the only genus in family Apterygidae). At around the size of a domestic chicken, kiwi are by far the smallest living ratites. Though they are thought to be most closely related to either cassowaries or moa, their evolutionary origin is still uncertain. Several kiwi species are endangered.
Prior to the arrival of humans in about 1300, New Zealand's only endemic mammals were two species of bat (the long-tailed bat (Chalinolobus) and the short-tailed bat (Mystacina)). The ecological niches that in other parts of the world were filled by creatures as diverse as horses, wolves and mice were taken up by birds (and, to a lesser extent, reptiles).
Kiwi are shy, nocturnal creatures with a highly developed sense of smell and, most unusual in a bird, nostrils at the end of their long, sharp bill. They feed by thrusting the bill into the ground in search of worms, insects, and other invertebrates; though they also take fruit and, if the opportunity arises, small crayfish, amphibians and eels.
Their adaptation to a terrestrial life is extensive: like all ratites they have no keel on the breastbone to anchor wing muscles, and barely any wings either: the vestiges are so small that they are invisible under the kiwi's bristly, hair-like, two-branched feathers. While birds generally have hollow bones to save weight and make flight practicable, kiwi have marrow, in the style of mammals. With no constraints on weight from flight requirements, some Brown Kiwi females carry and lay a single 450 gram egg.
The largest species is the Great Spotted Kiwi, Apteryx haastii, which stands about 450 mm high and weighs about 3.3 kg. (Males about 2.4 kg) It has grey-brown plumage with lighter bands. The female lays just one egg, with both sexes incubating. Population is estimated to be over 20,000, distributed through the more mountainous parts of northwest Nelson, the northern West Coast, and the Southern Alps.
The very small Little Spotted Kiwi, Apteryx owenii is unable to survive predation by imported pigs, stoats and cats and is extinct on the mainland and the most threatened of all kiwi. About 1000 remain on Kapiti Island and it has been introduced to other predator-free islands and appears to be becoming established. A docile bird the size of a bantam, it stands 250 mm high and the female weighs 1.3 kg. She lays one egg which is incubated by the male.