Story: Kiwi
Page 1 – A remarkable bird
Despite the fact that few New Zealanders have ever seen a kiwi in the wild, this nocturnal flightless bird has become an emblem both of the country and its people.
This iconic status is partly due to its unusual appearance. It has a long bill, small head, round body without a tail, and stocky legs, and is easily caricatured.
Call of the kiwi
Does the kiwi’s name come from the sound of its call? The male does claim its territory with a half-whistle, half-scream, usually at dusk, and females answer with a hoarser tone. But the sound is not kee-wee. In some species it is a single rising note repeated up to 10 times. If it was named for its call, then kree would be a more accurate representation. The bird is probably named for its similarity to the Polynesian kivi, a tropical curlew that also has a long beak.
Becoming flightless
Although it is a bird, the kiwi has been called an ‘honorary mammal’. 1 For millions of years New Zealand had no land mammals except bats. The ancestors of the kiwi took to the ground, filling a role similar to that of mammals such as badgers or hedgehogs in other parts of the world.
Mammalian features
Kiwi belong to not one, but several species. They all have mammal-like characteristics:
- Nostrils at the tip of the beak. Probing up to 10 centimetres into the soil, they can sniff out the worms, cicadas, wētā and fruit that they eat. Kiwi are one of the few birds with a powerful sense of smell.
- Cat-like whiskers at the base of the beak, which help the kiwi navigate at night.
- Notable ear openings, allowing good hearing.
- Feathers that are more like shaggy hair: they lack the barbs of most feathers.
- Tough, leathery skin.
- Heavy bones filled with marrow. Most birds’ bones are hollow and light for flight.
- Strong, heavy legs that allow them to run as fast as a person and to fight ferociously.
- Two functioning ovaries in females – birds normally have only one.
- 38ºC blood temperature – two degrees lower than most birds.
Evolution and arrival in New Zealand
Since the oldest known fossil kiwi is only about a million years old, its evolution is not yet fully understood. Certainly it is a member of the ratite group, like emu, ostrich or moa. Like other ratites, it has a flat breastbone without the usual raised keel to which wing muscles would be attached.
How the ancestors of kiwi arrived is also unclear. They may have been in New Zealand when it drifted away from Gondwana about 85 million years ago, or they may have flown there later (which seems unlikely), or walked there from island to island.
