Birds

Kiwi

Apteryx · also called kiwis

Vulnerable ↓ insectivoreomnivore Temperate forest Temperate grassland Mountains

A kiwi is a bird that has spent millions of years pretending to be a mammal. It is flightless and nocturnal, it lives in a burrow, it has whiskers and shaggy hair-like feathers and a low body temperature, and it hunts earthworms by smell using nostrils set at the very tip of its bill — the only bird built that way. Its egg is the largest, relative to body size, of any bird on Earth.

Overview

Kiwi are the genus Apteryx, five species, found only in New Zealand, in native forest, scrub, tussock grassland, and rough farmland. They are chicken-sized insectivores that probe soil and leaf litter for earthworms, grubs, centipedes, and spiders, plus fallen fruit, guided by smell and by touch-sensitive pits at the bill tip.

Honorary mammal

No wings or tail, heavy marrow-filled bones instead of air-filled ones, hair-like feathers, whiskers, burrows, a body temperature around 38 °C (low for a bird), and one of the best senses of smell of any bird. Kiwi pair for life, call at night to stay in contact, and in most species the male alone incubates the giant egg for 75–85 days, one of the longest incubations of any bird.

The egg

A female’s single egg is 15–25% of her body weight — the largest of any bird relative to size. It has a huge yolk, so the chick hatches fully feathered, eyes open, and feeds itself within a week with no food from the parents.

Status

The kiwi is Vulnerable overall and decreasing, around 68,000 birds left and falling ~2% a year where unmanaged. Stoats and dogs are the main killers — without predator control, about 95% of wild chicks die before breeding age. Survival now depends on trapping, raising chicks until they can fight off a stoat, and predator-free sanctuaries.

Kiwi: common questions

Why is a kiwi so different from other birds?

The kiwi evolved for millions of years on islands with no native land mammals, filling the ecological role that hedgehogs, shrews, and other small ground foragers occupy elsewhere. Freed from the need to fly and with no ground predators to escape, it lost its wings, tail, and light skeleton, grew heavy marrow-filled bones, took on shaggy hair-like feathers for insulation in the cool forest floor, became nocturnal, and developed a mammal-like reliance on smell and touch rather than sight. Its low body temperature, burrowing, whiskers, and territorial pair bonds all point the same way. Biologists sometimes only half-jokingly call the kiwi a mammal in a bird suit.

How can a small bird lay such a huge egg?

A female kiwi lays an egg that is roughly 15 to 25 percent of her body weight, compared with about 2 percent for a typical bird, and in the final days before laying the egg takes up so much of her abdomen that she can barely eat and has to fast. The likely explanation is evolutionary history. The kiwi is descended from larger ratite ancestors, possibly closer in size to a moa or a modern emu, and as the lineage shrank the egg did not shrink proportionally. The oversized egg has a big yolk, which produces a very well developed chick that hatches fully feathered, opens its eyes at once, and leaves the burrow to feed itself within about a week, with the parents providing no food at all.

What is killing New Zealand's kiwi?

Introduced mammalian predators, above all the stoat and the domestic dog. Stoats, brought to New Zealand in the 1880s to control rabbits, kill kiwi chicks in large numbers, and in unmanaged forest around 95 percent of chicks die before they reach breeding age, most of them to stoats. Dogs, both strays and pets, kill adult kiwi, which have no defence against a mammal that hunts by scent and can crush the bird's unprotected ribcage. Ferrets and cats take a further toll, and cars kill birds where roads cross kiwi habitat. Habitat clearance reduced kiwi range earlier, but today predation is the dominant threat, and it is why kiwi survive best on predator-free islands and in trapped and fenced sanctuaries.

Are kiwi related to the moa or to other flightless birds?

Kiwi are ratites, the group of flightless birds that also includes the ostrich, emu, cassowary, rhea, and the extinct moa and elephant birds. For a long time the kiwi was assumed to be the moa's closest relative, since both lived in New Zealand, but DNA has overturned that. The kiwi's nearest relative is actually the extinct elephant bird of Madagascar, and its ancestors are thought to have flown to New Zealand and become flightless there, separately from the moa, which had been in New Zealand far longer. So New Zealand ended up with two unrelated groups of giant and not-so-giant flightless birds.

Sources & further reading

Written by HideShark Editorial Team · reviewed by HideShark Science Desk. Published September 10, 2026. Last updated September 10, 2026.

Quick facts

Scientific name: Apteryx
Diet: Mostly soil and litter invertebrates found by probing, including earthworms, beetle and cicada larvae, centipedes, spiders, snails, and crickets, along with fallen fruit and some seeds and leaves, detected largely by smell and by touch-sensitive pits at the bill tip
The only bird with nostrils at the bill tip: Every other bird has its nostrils at the base of the bill near the face, but a kiwi has them at the very end, so it can sniff out worms and grubs underground, and it has one of the best senses of smell of any bird and one of the largest scent-processing regions in the brain
An enormous egg: A female kiwi lays a single egg that can weigh 15 to 20 percent, and in the little spotted kiwi up to about 25 percent, of her own body weight, the largest egg relative to body size of any bird, and the chick hatches fully feathered and able to feed itself within a week, with no parental feeding
More like a mammal than a bird: Kiwis have loose, shaggy, hair-like feathers, no functional wings or tail, heavy marrow-filled bones rather than the air-filled bones of flying birds, whiskers around the bill, a body temperature around 38 degrees Celsius which is low for a bird, burrows, and a strong territorial sense, a set of traits sometimes described as honorary mammal
They pair for life and the male incubates: Kiwis form long-term monogamous pairs that call to each other at night to keep contact, and in most species the male does all or most of the roughly 75 to 85 day incubation, one of the longest of any bird, sitting on the huge egg in the burrow
Fierce for their size: A kiwi defends its territory with loud calls and, if pressed, with powerful kicks from legs that make up about a third of its body weight and are tipped with sharp claws, and rival birds will fight hard
A national symbol under threat: The kiwi is the emblem of New Zealand and the informal name for its people, yet unmanaged mainland populations are falling by around 2 percent a year, and without predator control about 95 percent of wild kiwi chicks are killed before breeding age, mostly by stoats and dogs
Range: New Zealand only, on the North Island, South Island, Stewart Island, and several smaller offshore islands, in native forest, scrub, tussock grassland, and rough farmland, and in the case of the great spotted kiwi up into subalpine herbfields above the treeline, wherever there is soft ground to probe and dense cover for daytime burrows.
Conservation status: Vulnerable ↓ ≈ Of the five kiwi species, the little spotted kiwi is Near Threatened and stable, having been saved on predator-free islands, while the others range from Vulnerable to Endangered, with the total wild population estimated at around 68,000 birds and falling in unmanaged areas. Introduced stoats, ferrets, cats, and dogs are the main killers, taking eggs, chicks, and adults, alongside habitat loss and vehicle strikes, and the species now depends heavily on intensive management including trapping, the raising of chicks in captivity until they are large enough to fight off a stoat, and predator-free sanctuaries in the wild