Kiwi Bird: Behaviour, Diet, Breeding, Threats, and Conservation

By Eman Abdallah Kamel

This article covers the kiwi bird, including its species, physical characteristics, diet, behaviour, facts, reproduction, threats, and conservation.

Introduction

Kiwis are flightless birds endemic to New Zealand and belong to the family Apterygidae. They are more closely related to Australian emus and African ostriches than to the extinct New Zealand moas. Kiwis are an unofficial national symbol of New Zealand.

Did You Know?

The kiwi is similar in size to a chicken; it has neither wings nor a tail, and its plumage differs from that of other birds, resembling hair instead.

All New Zealand kiwi species are threatened: Okarito Brown Kiwis and Haast Tokoekas are nationally critical; North Island Brown Kiwis are seriously declining; Great Spotted Kiwis and Southern Tokoekas are gradually declining; and Little Spotted Kiwis are range-restricted.

Interest in ratites has increased due to the farming potential of ostriches, emus, and rheas for meat, skins, and feathers, as well as conservation efforts to protect endangered kiwis and cassowaries.

Great spotted kiwi: Image source: Department of Conservation, New Zealand Government.

Species

Physical Characteristics

Wings: Vestigial and hidden under feathers; no sternal keel for wing muscles.
Feathers: Bristly, hair-like, two-branched; lack barbules and aftershafts.
Bones: Contain bone marrow.
Preen gland: Absent.
Bill: Long, flexible, and touch-sensitive.
Eyes: Reduced pecten.
Vibrissae: Large bristles around the gape.
Tail: Absent; small pygostyle.

Little spotted kiwi. Image source: Wikimedia.org

Behaviour

The North Island brown kiwi is entirely nocturnal and inhabits the native forests of New Zealand. It can also live in diverse habitats, including pine forests, regenerating forests, grasslands, overgrown pastures, and dunes. Its habitat choice mainly depends on the availability of food and shelter, showing considerable adaptability to both natural and human-modified environments.
Kiwis are highly territorial, and evidence has shown that male North Island brown kiwis are more defensive than females.
Kiwi birds (both males and females) possess distinct, easily recognisable calls. While the calls of the North Island Brown Kiwi, Okarito Brown Kiwi, Southern Tokoeka, Haast Tokoeka, and Great Spotted Kiwi are similar to one another, the call of the Little Spotted Kiwi differs. These birds are most vocal in the winter and spring.
Kiwi birds have extremely slow growth rates compared to other birds; they continue to grow until the age of three or five, while their weight may not stabilise until they reach the age of four or six.

Diet

Kiwis mainly eat invertebrates, especially native worms over 0.5 metres long. They also eat berries, seeds, and leaves. Their diet varies because they live in diverse habitats.

Brown kiwi eat fungi, frogs, crayfish, eels, and earthworms. They get enough water from their food, helping them survive dry places like Kapiti Island. Being nocturnal also helps them avoid the heat and dehydration from the sun.

Did You Know?

The reproductive success of the kiwi is closely linked to its diet; these birds need to build up substantial energy reserves to get through the breeding season, so harsh conditions—such as droughts or floods—can cause reproductive rates to fall below normal levels.

Okarito kiwi. Image source: ebird.org

Breeding

Mating patterns: Most kiwis form long-term partnerships with high partner fidelity.
Territorial behaviour: Territory defence and polygamy depend mainly on parental demands, not resource or mate distribution.
Incubation: Some populations show deviations from solely paternal incubation.
Courtship: Bill-to-bill grunting occurs in North Island brown, great-spotted, and little-spotted kiwis.
Pre-mating behaviour: Great Spotted and North Island Brown Kiwis perform chasing, leaping, screeching, and snorting.
Daily behaviour: Pairs usually feed separately at night but spend about 20% of their days together.
First reproduction in captivity: Females: 3 years 9 months; males: 2 years 3 months.
Eggs: Female North Island brown kiwis living in the wild lay one or two eggs during the breeding season inside burrows ranging from 45 to 125 cm in length, whereas females in captivity may lay between four and six eggs—sometimes even as many as eight.

Did You Know?

It has been observed that the eggs of captive North Island brown kiwis are generally smaller (360 g) than those of wild kiwis (431 g), a difference attributed to the potential influence of diet.

Seasonal Egg-Laying Patterns: Kiwis’ egg-laying peaks from mid-winter to mid-spring. Although captive kiwis may lay eggs year-round, North Island brown, great-spotted, and little-spotted kiwis show seasonal patterns similar to wild birds, whether eggs are incubated naturally or artificially.

Southern brown kiwi. Image source: Wikimedia.org

Did You Know?

Female kiwis have two functional ovaries, and egg production requires an extra energy expenditure equal to about 100% of their basal metabolic rate for 34 days.

Incubation roles: North Island brown and little-spotted kiwis: males incubate, except during the first week. Okarito Brown Kiwis and Tokoekas: Both males and females share incubation. Southern Tokoeka family members may help incubate, sometimes leaving breeding males uninvolved.
Brood patch: Incubating males of all species and females of North Island Brown, Okarito Brown, and Tokoeka Kiwis develop a featherless patch on the lower belly to transfer heat to the eggs.
Great Spotted Kiwi: Males incubate during the day and early evening, while females incubate at night for 3–8 hours as males forage. Females do not appear to develop a brood patch.
Egg turning: North Island Brown Kiwis regularly turn their eggs.
Incubation timing: Incubation begins 1–7 days after laying.
Hatching: Kiwi chicks hatch by making a single puncture at the egg’s thinner air-cell end, then may take up to two days to break out. Their hatching weight is about 75% of the fresh egg’s weight, decreases until day eight, and begins increasing around day 12. Hatching success is low but can improve with artificial incubation. Their yolk-rich eggs, thin shells, long incubation, and damp burrows increase the risk of microbial infection.

Threats

Kiwi populations declined due to habitat loss, fires, and predators, especially after European settlement converted forests and scrubland into pasture.

Kiwi numbers have fallen from an estimated 12 million to around 68,000 today, with unmanaged populations declining by 2% annually.

Conversation

The Kiwi Recovery Programme integrates research with management actions to ensure they are properly planned, documented, and evaluated.
Kiwi populations are stable or increasing in managed areas, including sanctuaries, community-led projects, and offshore islands.
Rowi and little spotted kiwi numbers are increasing due to conservation efforts.
Although conservation management strategies have slowed the rate of decline, the other three species are still declining.

North Island brown kiwi. Image source: Wikimedia.org

Sources

About the author: Eman is a writer and engineer. She is interested in writing about birds and their facts.

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