Kiwi (genus Apteryx)

There is no more hilarious bird than the kiwi. Its funny body shape, strange beak, and bizarre biology make it a jolly combination of oddness. What a great bird!

There are actually five living species of kiwi, all of which are found in New Zealand. They are ratites, an order of flightless birds that includes giants like ostriches and emus. Unsurprisingly, kiwis spend their time on the ground, constructing burrows from a variety of materials in their habitats. They are found in numerous areas, including forests, scrublands and grasslands.

Kiwis have wings, they are just so small that they can’t be seen under the birds’ feathers. The smallest species of kiwi is the little spotted kiwi, at 25 cm in height, and 1.3 kg in weight. The largest is the great spotted kiwi, which grows to a height of 45 cm, and weighs 3.3 kg. Kiwis are covered in soft feathers, as they do not require hardened flight feathers. As another adaptation to their ground-dwelling lifestyle, kiwis have solid bones filled with marrow, unlike the hollow bones of other birds. Who needs to be lightweight when all you do is stumble around the forest floor?

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I can’t help but giggle when I look at a kiwi. Just look how weird they are! Image source: http://www.liveanimalslist.com/birds/kiwis.php

For the most part kiwis are nocturnal birds, though it seems that at least some of this nocturnality is a result of introduced predators. In areas where there are no predators, kiwis tend to venture around during the day. Still, kiwis have adapted quite well to the darkness. They have poor eyesight, but an exceptional sense of smell. A feature unique to kiwis is their nostril placement: while all other birds have their nostrils located at the base of the bill, kiwis have theirs at the tip. This allows kiwis to find yummy insects and worms with ease, even if they are underground.

Kiwis form strong monogamous pairs, and tend to stay together for life. Males court females through a variety of techniques, including grunts, leaps, and snorts. Kiwis produce massive eggs, and in fact have the biggest egg to body size ratio of any bird species. A kiwi egg can weigh a quarter of the weight of the female carrying it. While the egg is developing, the female kiwi must increase her food intake, eating three times as much as usual. By the time the egg is ready to be laid, it has grown so large that there is no room left in the female’s stomach, and thus she cannot eat until the egg is laid.

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A diagram showing the relative size of a female kiwi and her egg. Image source: Wikipedia

Largely due to introduced mammalian predators, such as stoats, cats, and dogs, all species of kiwi have experienced population declines. Two of the five species are listed as vulnerable, one is endangered, and one is critically endangered. It is estimated that only 5% of kiwi chicks survive to adulthood. Conservation programs, which have focused largely on providing predator-free sanctuaries for kiwis, have been reasonably successful. I am hopeful these guys will be around for a while to come, because they are just too silly to lose.

Cover image source: http://phys.org/news/2015-07-kiwi-bird-genome-sequenced.html

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