Apterygidae – Kiwis

Kiwis are flightless birds native to New Zealand, in the genus Apteryx and family Apterygidae. At around the size of a domestic chicken, kiwi are by far the smallest living ratites (which also consist of ostriches, emus, rheas, and cassowaries), and lay the largest egg in relation to their body size of any species of bird in the world.

DNA sequence comparisons have yielded the surprising 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, two of which are currently vulnerable, one of which is endangered, and one of which is critically endangered. All species have been negatively affected by historic deforestation but currently the remaining large areas of their forest habitat are well protected in reserves and national parks. At present, the greatest threat to their survival is predation by invasive mammalian predators.

They prefer subtropical and temperate podocarp and beech forests, but they are being forced to adapt to different habitat, such as sub-alpine scrub, tussock grassland, and the mountains. Kiwi have a highly developed sense of smell, unusual in a bird, and are the only birds with nostrils at the end of their long beaks. Kiwi eat small invertebrates, seeds, grubs, and many varieties of worms. They also may eat fruit, small crayfish, eels and amphibians. Because their nostrils are located at the end of their long beaks, kiwi can locate insects and worms underground using their keen sense of smell, without actually seeing or feeling them

Their adaptation to a terrestrial life is extensive: like all the other ratites (ostrich, emu, rhea and cassowary) they have no keel on the sternum to anchor wing muscles. The vestigial wings are so small that they are invisible under the bristly, hair-like, two-branched feathers. While most adult birds have bones with hollow insides to minimise weight and make flight practicable, kiwi have marrow, like mammals and the young of other birds. With no constraints on weight due to flight requirements, brown kiwi females carry and lay a single egg which may weigh as much as 450g. Like most other ratites, they have no preen gland. Their bill is long, pliable and sensitive to touch. Their feathers lack barbules and aftershafts, and they have large vibrissae around the gape. They have 13 flight feathers, no tail and a small pygostyle. Their gizzard is weak and their caecum is long and narrow

Kiwi are shy and usually nocturnal. Their mostly nocturnal habits may be a result of habitat intrusion by predators, including humans. In areas of New Zealand where introduced predators have been removed, such as sanctuaries, kiwi are often seen in daylight.

Once bonded, a male and female kiwi tend to live their entire lives as a monogamous couple. During the mating season, June to March, the pair call to each other at night, and meet in the nesting burrow every three days. These relationships may last for up to 20 years.

The kiwi is a national symbol of New Zealand, and the association is so strong that the term Kiwi is used internationally as the colloquial demonym for New Zealanders.