Biologists reveal a unique feature of kiwi birds from New Zealand

The kiwi bird, which is endemic to New Zealand, has unique characteristics: it cannot fly, has nostrils at the tip of its beak, and lays eggs of enormous size. Kiwis are nocturnal, which makes their encounters with humans rare.

In addition, their number is gradually decreasing. However, thanks to the efforts of ecologists, active measures are being taken to preserve this species. Discover wildlife tells about it.

The name "kiwi" comes from the characteristic piercing cry of males, reminiscent of "kee-wee, kee-wee". They use these sounds to attract the attention of females. In return, females make more sonorous sounds.

Kiwis have a pear-shaped body and are comparable in size to a chicken. The largest species, the large spotted kiwi, reaches 45 cm in height and weighs up to 2.2 kg (males). Females are slightly larger: about 50 cm in height and up to 3 kg in weight.

There are five types of kiwi in nature:

• large spotted,
• ocarito,
• brown,
• southern brown,
• and small spotted.

Thanks to the efforts of conservationists, the number of small spotted and okarito is increasing. At the same time, the populations of large spotted and southern brown kiwis are rapidly declining, while the number of brown kiwis remains stable.

According to the charity organization Save the Kiwi, there are about 68,000 left in the world. The population is declining due to predators (ermines, ferrets, dogs, cats) and loss of natural habitat.

Small, isolated populations also have lower genetic diversity, making them vulnerable to disease and fire.

According to the New Zealand Department of Conservation, stoats pose the greatest danger to chicks, and dogs to adults. Ferrets and cats also prey on kiwis.

The chicks remain vulnerable until they reach a weight of about 1 kg, after which they become able to defend themselves.

Kiwis inhabit forests, scrublands, agricultural lands, sand dunes, and mangroves. During the day, they hide in holes, tree hollows, or under dense vegetation, and at night they go out in search of food.

After dark, kiwis go in search of food, consuming small invertebrates, fallen leaves, and fruits. Despite its very small eyes, the bird navigates in the dark thanks to its extremely sensitive sense of smell. It is the only bird in the world with external nostrils at the tip of its beak.

Kiwis walk almost silently thanks to the fleshy pads on their feet. They tap their beaks on the ground, plunging them into the soil in search of earthworms and larvae. They also use their paws to shovel the ground and forage for food.

Kiwi courtship looks unusual: the male follows the female, making a characteristic sound and touching her with his beak. If the female is not interested, she runs away, but if she is, the pair can mate three or more times a night.

The breeding season lasts from June to March, when there is plenty of food. Kiwis usually form monogamous pairs, and the female lays one egg in a burrow. Incubation lasts from 70 to 80 days.

The chick hatches with a residual yolk sac that provides nutrition for the first 10 days. After that, it starts looking for food on its own.

Kiwi eggs are disproportionately large relative to the bird's body size. The Guinness Book of World Records states that the southern brown kiwi lays the largest eggs relative to its weight. For example, a female weighing 1.7 kg laid an egg weighing 406 g, which is almost 25% of her weight.

Despite significant progress in the conservation of these birds, their numbers in New Zealand continue to decline. The population recovery plan for 2018-2028 envisages increasing the number of kiwis to 100,000. The strategy includes environmental protection, predator control, and breeding programs.

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