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Ratites - The Kiwi

By Edited Apr 13, 2016 0 0

Flightless Birds

The New Zealand Kiwi

The Kiwi is endemic to New Zealand. It is also that country's national symbol. It is an emblem for army regiments and during World War I, its shape was carved into the chalk hills above Sling Camp in England. It also appears on the Coat of Arms of the Auckland University College. 'Kiwi' was the brand name of a shoe polish which was launched in Melbourne in 1906. The term 'Kiwi' is now in common usage as denoting a New Zealander.

Kiwis were originally found from sea level to 1,200 metres, occupying moist coniferous forests. Continual clearing of this primeval forest has forced kiwis into other habitats. A large commercial pine plantation now supports brown kiwis on North Island.

The name is derived from the ringing call of the male. The female has a hoarse, throaty call. The kiwi is quite vocal keeping in touch with its mate through an assortment of grunts, sniffles and growls. They snuffle audibly when searching for food. It is believed the snuffling may be caused by a valve opening and closing behind the nostrils. As the nostrils are located at the tip of the beak, the valve prevents inhalation of dirt and dust as the bird probes about for food.

The kiwi is a ratite. Other living ratites are the ostrich, emu, cassowary and rhea. Ratites are flightless birds. The breastbone (sternum) has no keel so there is no attachment place for the wing muscles. The moa and elephant bird were ratites but are now extinct.

On the kiwi, the vestigial wings are almost invisible and only two inches long. The plumage consists of coarse, bristly, hair-like feathers. Two feathers come off each shaft. There is no tail. The kiwi's main form of defence is the three strong toes which have razor-sharp claws. It is also an extremely fast runner.

Most birds of flight have hollow bones which reduces the weight of the bird. The bones of the kiwi contain marrow like the bones of mammals. Contrary to other birds, kiwi females have a functioning pair of ovaries. The kiwi is the size of a domestic chicken with the little spotted kiwi being the bantam version. In relation to their body size, kiwis lay huge eggs (the same size as an ostrich egg and ¼ of the kiwi's body weight). Kiwis bond for life and have great fidelity to their home areas. They will stay in their territory for weeks even when logging has removed every tree.

The kiwi is shy and very territorial. They are nocturnal and prefer subtropical and temperate areas. However they have been forced to adapt to sub-alpine scrub, grasslands and mountains. They can only see about six feet at night and two feet during daylight hours. They do have a highly developed sense of smell which enables them to smell insects and worms underground.

The kiwi is unique in that the nostrils are located at the tip of the beak, which is very long, slender and flexible. Kiwis are omnivorous eating fruit, seeds, berries, grubs, eels, amphibians and all sorts of worms. It digs into the ground with the sharp talons then pokes its long beak into the soft ground.

Kiwis usually pair for life. A burrow may be excavated by the male, sometimes with help from the female. A typical burrow is 20 to 200cm in length with a chamber at the end large enough for both birds. It will have one entrance. Kiwis also nest under tree roots or in hollow logs. Burrows are used for many years allowing the foliage to become well established found the entrance, concealing the opening.

Depending on the species, a clutch consists of one or two smooth, ivory to greenish-white eggs. To lay such a huge egg, the female trebles her food intake prior to laying. The male incubates an egg as soon as it is laid. If the female then decides she'll add another egg - this could be 25 to 30 days later - the male may spend much longer than the 11 week incubation period needed for one egg. He may lose a third of his body weight over this period. The chicks do not have an egg tooth but use their feet to kick their way out of the shell.

When the chick hatches it has its shaggy adult plumage. It lives in the nest, living off the remains of the egg yolk, for six to ten days. It stays for a time with the male but is completely independent at two weeks of age. It then goes off foraging for itself but won't reach adult size until the age of 18 to 20 months.

There are four species.

Apteryx haastii, or great spotted kiwi, has an estimated height of 45cm and weighs about 3.6kg. They are light brown with lighter spots. Females lay a single egg and share incubation duties.

Great Spotted Kiwi

Apteryx owenii, or little spotted kiwi, is the size of a bantam. It was originally from the South Island. They were later released on Kapiti Island. They weigh about 0.9 to 1.9kg. The female is slightly larger than the male. The plumage is a pale, mottled grey with fine white mottling. It has a few, fine whiskers round the base of the beak which are highly modified to form long tactile bristles, helping the animal find its way in the dark and compensating for the poor eyesight. The eyes are small and the ears unusually large.

The hen lays 1 to 2 eggs and the male looks after the incubation. Its egg is the largest in comparison of the kiwi species, equivalent to 26% of its own weight.

Little Spotted Kiwi

Apteryx rowi, or Okarito brown kiwi, is endemic to a restricted area of the Okarito forest on the west coast of the South Island. The rowi, as it is known, was only identified as a distinct species in 2003. It has soft, slightly greyish plumage and sometimes has white feathers on the face. It is critically endangered.

Apteryx mantelli, or North Island brown kiwi, has a territory of 2 to 100 hectares depending on the availability of food. It has a good chance of avoiding extinction if predator management can be effected. It is a prolific breeder but needs to be as around 90% of kiwi chicks die in their first six months. Seventy percent of these are killed by cats and stoats. Around 5% survive to adulthood but those that reach adulthood go on to live into their 60s.

North Island Brown Kiwi

The kiwi is highly valued by the Maoris for its feathers. Ceremonial cloaks are adorned with the shaggy plumage. Habitat destruction, introduced predators and death on the roads are all hazards that face the kiwi.

Maori Cloak

The kiwi is a true icon of New Zealand. The New Zealand people themselves are commonly referred to as 'kiwis'.

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