North Island Brown Kiwi (Apteryx mantelli): Facts and Habitat

What does a North Island brown kiwi look like?

The North Island brown kiwi is a round, pear-shaped bird with no visible wings and no tail. Its feathers are dark brown, streaked with reddish brown and black, and they are loose and spiky, so they look and feel more like coarse hair than plumage. Long whisker-like feathers grow around the base of the bill.

The bill is long, pale and slightly down-curved. Uniquely among birds, the nostrils sit at its very tip. The legs are short, thick and powerful, with strong toes and sharp claws used for digging and for fighting other kiwi. The eyes are small, and kiwi rely more on smell, touch and hearing than on sight.

Inside, the kiwi is just as unusual. Its wings are tiny stubs a few centimeters long, hidden beneath the feathers. Its breastbone has no keel for flight muscles, and its bones contain marrow rather than being hollow like those of most flying birds. Its body temperature, about 38 °C (100 °F), is lower than that of most birds. These traits have earned the kiwi the nickname “honorary mammal.”

How big is a North Island brown kiwi?

Kiwi are the smallest of the ratites, the group of flightless birds that also includes ostriches, emus and cassowaries. Females are clearly larger and heavier than males, and they also have longer bills.

Typical adults weigh around 2 kg (4.4 lb) for males and 2.7 kg (6 lb) for females. That makes the North Island brown kiwi one of the larger kiwi species, though the great spotted kiwi of the South Island is bigger.

Where does the North Island brown kiwi live?

The species lives in scattered populations across the northern two-thirds of the North Island. Its strongholds are Northland, the Coromandel Peninsula, the Bay of Plenty, Gisborne and Hawke’s Bay, the Tongariro area, Taranaki and Whanganui. It also lives on islands such as Little Barrier, Kawau and Ponui, and has been moved to predator-free islands and fenced sanctuaries, including Motuora and Sanctuary Mountain Maungatautari.

Scientists recognize four genetically distinct forms: Northland, Coromandel, Western and Eastern brown kiwi. They are managed separately to keep their differences.

Dense native lowland and coastal forest is the preferred habitat, but this kiwi is surprisingly adaptable. It also lives in pine plantations, scrub, regenerating bush, overgrown pasture, wetland edges and even sand dunes, as long as it has shelter and soft soil for feeding. By day it sleeps in a burrow, a hollow log or tree, or under dense vegetation, and it often has several resting places in its territory.

What does the kiwi eat and how does it find food?

The North Island brown kiwi feeds at night on the forest floor. Invertebrates make up about 85–95 percent of its diet: earthworms, the larvae of beetles, cicadas and moths, spiders, centipedes, crickets and weta. It also eats some fallen fruit and leaves.

A foraging kiwi walks slowly, tapping the ground with its bill and probing into leaf litter, rotten wood and soil. The nostrils at the bill tip let it smell prey underground, and tiny sensory pits at the tip detect the vibrations of moving worms and grubs. You can read more in Can birds smell?

Kiwi often snuffle and sneeze while feeding to clear soil from their nostrils. They swallow grit and small stones, which help grind food in the gizzard.

Behavior and calls

North Island brown kiwi are solitary or live as pairs, and adults defend a territory. Neighbors are usually kept apart by calling, but kiwi fight fiercely when needed, leaping and slashing with their claws.

Males and females sound different. The male gives a high, rising whistle repeated about 15–25 times, while the female answers with a slower, lower, hoarse cry repeated about 10–20 times. Pairs often duet, and calling is most frequent on dark nights, shortly after dusk and before dawn.

Breeding and the giant egg

Pairs usually stay together for many years, sometimes for life. Unlike most kiwi species, the North Island brown kiwi can lay eggs in any month, with a peak from June to November. A clutch has one or two eggs laid about three weeks apart, and a pair may raise up to two clutches a year.

The egg is enormous: on average about 12.4 x 8 cm (4.9 x 3.1 in) and roughly 430 g (15 oz), which can be about a fifth of the female’s weight. Only the male incubates, for about 75–90 days, and he may lose a lot of weight doing so. The full story is in How big is a kiwi egg?

Chicks hatch fully feathered, like miniature adults, and live off the remaining yolk for their first days. They first leave the nest after about a week and soon feed on their own. The parents do not feed them. Wild females usually begin breeding at about three to five years old.

How long do kiwi live?

Kiwi are long-lived birds. Banded wild North Island brown kiwi have been recorded at more than 20 years old, and experts estimate they may live to about 40 years where predators are controlled. Captive brown kiwi have lived to about 35 years. In some unmanaged areas, life is much shorter: in Northland, dogs and road traffic keep the average lifespan of adults to around 14 years.

Predators and threats

Before people arrived, New Zealand had no land mammals except bats, and kiwi evolved with few ground predators. Introduced mammals are now their biggest threat. Stoats and cats kill most chicks, while dogs and ferrets kill adults. A single roaming dog can wipe out a local kiwi population; one dog in Northland is thought to have killed around 500 kiwi in a few weeks in the 1980s. The impact of stoats is explained in stoats in New Zealand.

In areas without predator control, fewer than one chick in ten survives to adulthood. Chicks become fairly safe from stoats once they weigh about 1–1.2 kg (2.2–2.6 lb). Habitat loss, cars, badly set traps and fragmentation of small populations add to the pressure.

Conservation status

The IUCN Red List classifies the North Island brown kiwi as Vulnerable, with a decreasing population. The population fell from about 35,000 in 1996 to roughly 26,000 in 2015, and mainland populations without management decline by around 2–2.5 percent a year. Where predators are controlled, populations are stable or growing.

Conservation work includes trapping and poisoning of predators, Operation Nest Egg (hatching eggs and raising chicks in safety until they are big enough to defend themselves), training dogs to avoid kiwi and moving birds to safe islands and sanctuaries. The wider picture for all five species is covered in Are kiwi birds endangered?

The kiwi’s closest relatives

There are five living kiwi species, all found only in New Zealand: the North Island brown kiwi, the rowi (Okarito kiwi), the tokoeka (southern brown kiwi), the great spotted kiwi and the little spotted kiwi. Until the 1990s the North Island bird was lumped with the South Island tokoeka as a single “brown kiwi,” and genetic studies later showed they are separate species.

For a long time scientists assumed kiwi were close cousins of the moa, the giant extinct flightless birds that once shared New Zealand with them. DNA studies have overturned that idea. The kiwi’s closest known relatives are the extinct elephant birds of Madagascar, and among living birds it is more closely related to emus and cassowaries than the moa ever were. This suggests that the kiwi’s ancestors flew to New Zealand and only later lost the ability to fly.

Myths and facts about kiwi

Myth: the bird was named after the fruit. It is the other way round. The fuzzy brown fruit, once called the Chinese gooseberry, was renamed kiwifruit by New Zealand exporters around 1959, after the national bird. The name kiwi itself comes from Maori and probably imitates the bird’s call.

Myth: kiwi find food by smell alone. Smell matters a great deal, but research shows that kiwi also use the sensitive pits at the tip of the bill to feel prey moving in the soil, and probably listen for it too. They switch between senses depending on the conditions.

Fact: kiwi are fierce fighters. Their quiet, shy image hides a strong territorial streak. Rival kiwi jump at each other and kick with sharp claws, and fights between neighbors can cause serious injuries.

Kiwi and people

To Maori, kiwi are a taonga (treasure) under the protection of Tane Mahuta, god of the forest, and kiwi feathers were woven into prized cloaks called kahu kiwi. Today feathers come only from birds that die naturally or in accidents.

The kiwi became a New Zealand emblem in the late 19th century. New Zealand soldiers were nicknamed “Kiwis” during the First World War, and the name now applies to all New Zealanders. A kiwi appears on the one-dollar coin, and the New Zealand dollar itself is nicknamed “the kiwi.” Other birds that cannot fly are listed in our guide to flightless birds.