The Fanciful, Flightless Kiwi

photo credit: NatGEO website

In New Zealand’s fern-carpeted forests lives a very strange and reclusive creature. This nocturnal bird ventures out cautiously at night to probe for insects in the leaf litter. Its rounded body is covered in short, shaggy brown feathers, and its hunched posture makes it more reminiscent of a small, scurrying mammal than a bird. To round out its unique resume, this unique bird has inspired a namesake – an egg-shaped, furry brown fruit. Ladies and gentlemen…the Kiwi.

Physiologically, kiwis are incredibly unique. All five species of kiwi are members of the genus Apteryx, derived from the Greek word meaning “wingless.” While kiwis are not truly without wings, these bipedal birds have wings that are so disused they seem almost like an anatomical afterthought. Like other birds in its overarching group, called ratites, kiwis lack a keeled breastbone and the strong wing muscles that would be anchored to such a structure. These solid birds have so enthusiastically abandoned flight that their bones contain marrow, making them proportionally much heavier than their lighter, hollow-boned cousins. Kiwi feathers are downy and lack the barbules that give other birds their smooth appearance. As if to compound its devotion to its punk-rock plumage, these birds also lack preen glands with which to oil and organize their feathers.

Kiwis are physiologically adapted to feed and breed. The kiwi’s flexible bill curves downward to facilitate shuffling leaf litter, and their nostrils are positioned at the very tip, enabling the birds to sniff out buried insects with their strong sense of smell. With strong, heavy bones to support large eggs, the female kiwi is able to produce the avain world’s largest egg in proportion to her body. These chicken-sized birds produce an egg six times larger than an average chicken egg, weighing almost one-quarter of the weight of the female herself.

During the breeding season, male kiwis excavate underground burrows and prepare a nest area. His female partner must invest a large amount of energy in producing such an enormous egg. For a month after breeding, the female bird consumes up to three times her normal amount of food per day, ensuring that she has enough energy to survive the laying process. Several days before laying begins, the female stops eating – the egg has taken up so much space inside her that her stomach can no longer hold food. After the egg is laid, the male generally incubates for the required two to three months, perhaps because of the enormous amount of effort expended earlier by his mate. Males are devoted parents, leaving the nest so infrequently that their weight can decrease by one-third. Newly-hatched kiwis are covered in adult plumage, and survive in the nest for several days by slowly consuming the reserve yolk in its stomach. After it gains enough strength, the young bird accompanies its male parent on its first search for food.

Today, perhaps as a testament to their generally calm and hard-working demeanor, New Zealanders are called “Kiwis.” It seems that this shy bird just cannot escape notice – its distinctive characteristics have earned it the respect of a nation.

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