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Kiwi (bird)

life science Maturity 7-9 Next article →

The kiwi is a unique group of flightless birds found only in New Zealand.

Am media-v-602297
Am media-v-602297

These birds belong to the order Apterygiformes and the family Apterygidae. They are classified as ratites, a group of birds that cannot fly. This group includes much larger animals like ostriches, emus, and rheas. Even though they are small, kiwi are internationally famous. In fact, the term "Kiwi" is used as a nickname for people from New Zealand.

1898 kiwi 6d red
1898 kiwi 6d red

Kiwi have evolved many specialized physical traits for a life on the ground. Their wings are vestigial, meaning they are tiny and hidden under bristly, hair-like feathers. They also lack a keel on their sternum, which is the bone needed to anchor flight muscles. Unlike most birds, kiwi have bones filled with marrow rather than being hollow. Their feathers are unique because they lack barbules and aftershafts. They also have no tail and possess very small eyes.

Because their eyes are so small relative to their body mass, kiwi rely on other senses. They have a highly developed olfactory chamber, which allows for a keen sense of smell. Most importantly, they are the only birds with nostrils located at the very tip of their long beaks. This helps them detect prey like worms, grubs, and insects underground. While they use smell, they also use hearing and touch to find food.

Apteryx mantelli -Rotorua, North Island, New Zealand-8a
Apteryx mantelli -Rotorua, North Island, New Zealand-8a

There are five living species of kiwi, each with different traits and habitats. The great spotted kiwi is the largest, with females weighing up to 4 kilograms. The little spotted kiwi is much smaller, roughly the size of a bantam chicken. The North Island brown kiwi is the most common, with about 35,000 individuals remaining. In contrast, the Haast southern brown kiwi is very rare, with only about 300 left in the wild.

Three kiwi species models in Auckland museum
Three kiwi species models in Auckland museum

Reproduction in kiwi is also quite remarkable. Female kiwi lay eggs that are enormous compared to their body size. An egg can weigh up to 20% of the female's total body weight.

KiwiEggRatio
KiwiEggRatio

In some species, like the great spotted kiwi, both parents work together to incubate the egg. In the North Island brown kiwi, the male is responsible for incubation. Many kiwi are monogamous, meaning they stay with one partner for their entire lives.

For a long time, scientists believed kiwi were closely related to the extinct moa of New Zealand. However, modern DNA sequence comparisons have changed this understanding. Research shows that kiwi are actually more closely related to the extinct elephant birds of Madagascar. Among living ratites, they are more closely related to emus and cassowaries. A 2013 study of the extinct genus Proapteryx suggests that kiwi ancestors may have once been able to fly.

Okarito kiwi 2
Okarito kiwi 2

Today, kiwi face significant challenges to their survival. Historic deforestation has reduced their natural habitats. Currently, the greatest threat is predation by invasive mammals like cats, stoats, and pigs. While many kiwi live in protected national parks and forest reserves, they remain vulnerable. Conservation efforts focus on protecting these birds and managing the predators that threaten them.

NZ road sign W18-3.9
NZ road sign W18-3.9
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🖼️ Images & Media (13)
File:Am media-v-602297.jpg
Am media-v-602297.jpg
File:Am media-v-602370.jpg
Am media-v-602370.jpg
File:Okarito kiwi 2.jpg
Okarito kiwi 2.jpg
File:Tokoeka.jpg
Tokoeka.jpg
File:Apteryx mantelli -Rotorua, North Island, New Zealand-8a.jpg
Apteryx mantelli -Rotorua, North Island,...
File:Three kiwi species models in Auckland museum.jpg
Three kiwi species models in Auckland museum.jpg
File:Transactions and proceedings of the New Zealand Institute (1870) (14728011026).jpg
Transactions and proceedings of the New...
2024-11-26_2203_Kiwi.wav
File:KiwiEggRatio.svg
KiwiEggRatio.svg
File:NZ road sign W18-3.9.svg
NZ road sign W18-3.9.svg
File:TWC Wildlife Centre• Stewart Nimmo • MRD 8502.jpg
TWC Wildlife Centre• Stewart Nimmo • MRD 8502.jpg
File:Detail of bottom border of Māori kahu kiwi.jpg
Detail of bottom border of Māori kahu kiwi.jpg

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