| Kiwi | |
|---|---|
| North Island Brown Kiwi (Apteryx mantelli) in captivity | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Superorder: | Palaeognathae |
| Order: | Apterygiformes Haeckel, 1866 |
| Family: | Apterygidae Gray, 1840[1] |
| Genus: | Apteryx Shaw, 1813[1] |
| Type species | |
| Apteryx australis Shaw & Nodder, 1813[2] |
|
| Species | |
|
Apteryx haastii Great Spotted Kiwi |
|
| Synonyms | |
|
Stictapteryx Iredale & Mathews, 1926 |
|
Kiwi are flightless birds endemic to New Zealand, in the genus Apteryx and family Apterygidae.
At around the size of a domestic chicken, kiwi are by far the smallest living ratites and lay the largest egg in relation to their body size of any species of bird in the world.[3] There are five recognised species, all of which are endangered; all species have been adversely affected by historic deforestation but currently large areas of their forest habitat are well protected in reserves and national parks. At present, the greatest threat to their survival is predation by invasive mammalian predators.
The kiwi is a national symbol of New Zealand, and the association is so strong that the term Kiwi is used all over the world as the colloquial demonym for New Zealanders.
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There are five known species of kiwi, as well as a number of subspecies.
Analysis of mitochondrial DNA, ecology, behaviour, morphology, geographic distribution and parasites of the North Island Brown Kiwi has led scientists to propose that the Brown Kiwi is three distinct species. The North Island Brown Kiwi; the Okarito Brown Kiwi (Rowi), whose distribution is restricted to a single site on the West Coast of the South Island of New Zealand; and a third distinct population of the North Island Brown Kiwi, the Southern Tokoeka, distributed in the lowland forest to the north of Franz Josef glacier in the South Island and on Stewart Island/Rakiura, with a small population near Haast being another possibly distinct species, the Haast Tokoeka.
It was long presumed that the kiwi was closely related to the other New Zealand ratites, the moa. However, recent DNA studies indicate that the Ostrich is more closely related to the moa and the kiwi is more closely related to the Emu and the cassowaries. This theory suggests that the ancestors of the kiwi arrived in New Zealand from elsewhere in Australasia well after the moa. According to British scientists, the kiwi may be an ancient import from Australia. Researchers at Oxford University have found DNA evidence connected to Australia's Emu and the Ostrich of Africa. Upon examining DNA from the moa, they believe that the kiwi is more closely related to its Australian cousins.[7]
Before the arrival of humans in the 13th century or earlier, New Zealand's only endemic mammals were three species of bat, and the ecological niches that in other parts of the world were filled by creatures as diverse as horses, wolves and mice were taken up by birds (and, to a lesser extent, reptiles).
Kiwi are shy and usually nocturnal. Their mostly nocturnal habits may be a result of habitat intrusion by predators, including humans. In areas of New Zealand where introduced predators have been removed, such as sanctuaries, kiwi are often seen in daylight. They prefer subtropical and temperate podocarp and beech forests, but they are being forced to adapt to different habitat, such as sub-alpine scrub, tussock grassland, and the mountains.[2] Kiwi have a highly developed sense of smell, unusual in a bird, and are the only birds with nostrils at the end of their long beaks. Kiwi eat small invertebrates, seeds, grubs, and many varieties of worms. They also may eat fruit, small crayfish, eels and amphibians. Because their nostrils are located at the end of their long beaks, Kiwi can locate insects and worms underground using their keen sense of smell, without actually seeing or feeling them.[2]
Once bonded, a male and female kiwi tend to live their entire lives as a monogamous couple. During the mating season, June to March, the pair call to each other at night, and meet in the nesting burrow every three days. These relationships may last for up to 20 years.[8] They are unique among other birds in that they have a functioning pair of ovaries.[2] Kiwi eggs can weigh up to one quarter the weight of the female. Usually only one egg is laid per season. The kiwi lays the biggest egg in proportion to its size of any bird in the world,[9] so even though the kiwi is about the size of a domestic chicken, it is able to lay eggs that are about six times the size of a chicken's egg.[10][11] Eggs are smooth in texture, and are ivory or greenish white.[12] The male incubates the egg, except for the Great Spotted Kiwi, A. haastii, in which both parents are involved. The incubation period is 63–92 days.[2] Producing the huge egg places a lot of demands on the female. For the thirty days it takes to grow the fully developed egg the female must eat three times her normal amount of food. Two to three days before the egg is laid there is little space left inside the female for her stomach and she is forced to fast.[13]
Their adaptation to a terrestrial life is extensive: like all ratites they have no keel on the breastbone to anchor wing muscles, and barely any wings. The vestiges are so small that they are invisible under the bristly, hair-like, two-branched feathers of the kiwi. While birds generally have bones with hollow insides to minimise (weight) and make flight practicable, kiwi have marrow, in the style of mammals. With no constraints on weight due to flight requirements, some Brown Kiwi females carry and lay a single 450 g (16 oz) egg. Like most other ratites, they have no preen gland. Their bill is long, pliable, and sensitive to the touch, and their eyes have a reduced pecten. Their feathers lack barbules, and aftershafts, and they have large vibrissae around the gape. They have 13 flight feathers, no tail, just a small pygostyle. Finally, their gizzard is weak and their caecum is long and narrow.[2]
The kiwi gets its name from the Maori people's imitation of its cry. The Māori traditionally believed that kiwi were under the protection of Tane Mahuta, god of the forest. They were used as food and their feathers were used for kahu kiwi – ceremonial cloaks.[14] Today, while kiwi feathers are still used, they are gathered from birds that die naturally or through road accidents or predation. Kiwis are no longer hunted, and some Maori consider themselves their guardians.[15]
The first kiwi specimen to be studied by Europeans was a kiwi skin brought to George Shaw by Captain Andrew Barclay aboard the ship Providence, who was reported to have been given it by a sealer in Port Jackson (Sydney Harbour) around 1811. George Shaw gave the bird its scientific name and drew sketches of the way he imagined a live bird to look which appeared as plates 1057 and 1058 in volume 24 of The Naturalist's Miscellany in 1813.
In 1851, London Zoo became the first zoo to keep kiwis. The first captive breeding took place in 1945.[16] As of 2007 only 13 zoos outside New Zealand hold kiwis.[17] The Frankfurt Zoo has 12, the Berlin Zoo has 7, Walsrode Bird Park has 1, the Washington Zoo has 3, the Avifauna Bird Park in the Netherlands has 3, the San Diego Zoo has 5, the San Diego Wild Animal Park has 1, the Smithsonian National Zoological Park has 5, the Smithsonian Conservation Biology Institute has 1 and the Columbus Zoo and Aquarium in Columbus, Ohio has 3.[18]
The Māori language word kiwi ( /ˈkiːwiː/ kee-wee)[19] is generally accepted to be "of imitative origin" from the call.[20] However, linguists derive the word from Proto-Nuclear Polynesian *kiwi, which refers to Numenius tahitiensis, the Bristle-thighed Curlew, a migratory bird that winters in the tropical Pacific islands.[21] With its long decurved bill and brown body, the curlew resembles the Kiwi. So when the first Polynesian settlers arrived, they simply reused the word for the new-found bird.[15] The genus name Apteryx is derived from Ancient Greek "without wing": a-, "without" or "not"; pterux, "wing".[22]
The kiwi as a symbol first appeared in the late 19th century in New Zealand regimental badges. It was later featured in the badges of the South Canterbury Battalion in 1886 and the Hastings Rifle Volunteers in 1887. Soon after, the kiwi appeared in many military badges, and in 1906 when Kiwi Shoe Polish was widely sold in the UK and the US the symbol became more widely known.
During the First World War, the name "kiwi" for New Zealand soldiers came into general use, and a giant kiwi (now known as the Bulford Kiwi), was carved on the chalk hill above Sling Camp in England. Use has now spread so that now all New Zealanders overseas and at home are commonly referred to as "kiwis".
The kiwi has since become the most well-known national symbol for New Zealand, and the bird is prominent in the coat of arms, crests and badges of many New Zealand cities, clubs and organisations; at the national level, the red silhouette of a kiwi is in the center of the roundel of the Royal New Zealand Air Force.[12][23]
The New Zealand dollar is often referred to as "the kiwi dollar".[24]
Introduced mammalian predators, namely stoats, dogs, ferrets, and cats, are the number one threat to kiwi. Other threats include habitat modification/loss and road strike. The restricted distribution and small size of some kiwi populations increases their vulnerability to inbreeding.
Stoats are responsible for approximately half of kiwi chick deaths in many areas through New Zealand. Cats also to a lesser extent prey on kiwi chicks. The combined effect of these predators results in only 10% of kiwi chicks surviving to the age of six months. Young kiwi chicks are vulnerable to stoat predation until they reach about 1 - 1.2 kg in weight, at which time they can usually defend themselves.
Ferrets and dogs often kill adult kiwi. These predators can cause large and abrupt declines in populations. In particular, dogs find the strong distinctive scent of kiwi irresistible and easy to track, such that they can catch and kill kiwi in seconds. Motor vehicle strike is a threat to all kiwi where roads cross through their habitat. Badly set possum traps also kill or maim a large number of kiwi each year.[25]
Nationwide studies show that on average only five percent of kiwi chicks survive to adulthood. However, in areas under active pest management, survival rates for North Island brown kiwi can be far higher. For example, prior to a joint 1080 poison operation undertaken by DOC and the Animal Health Board in Tongariro Forest in 2006, 32 kiwi chicks were radio-tagged. 57% of the radio-tagged chicks survived to adulthood. Thanks to ongoing pest control, the adult kiwi population at Tongariro has almost doubled since 1998.[26]
In 2000, the Department of Conservation set up five kiwi sanctuaries focused on developing methods to protect kiwi and to increase their numbers. There are three kiwi sanctuaries in the North Island and two in the South Island:
A number of other mainland conservation islands and fenced sanctuaries have significant populations of kiwi, including:
Operation Nest Egg is a programme run by the BNZ Save the Kiwi Trust - a partnership between the Bank of New Zealand, the Department of Conservation and the Royal Forest and Bird Protection Society. Kiwi eggs and chicks are removed from the wild and hatched and/or raised in captivity until big enough to fend for themselves – usually when they weigh around 1200 grams. They are then returned to the wild. An Operation Nest Egg™ bird has a 65% chance of surviving to adulthood – compared to just 5% for wild-hatched and raised chicks.[27] The tool is used on all kiwi species except little spotted kiwi.
In 2004, anti-1080 activist Phillip Anderton posed for the New Zealand media with a kiwi he claimed had been poisoned. An investigation revealed that Anderton lied to journalists and the public.[28] He had used a kiwi that had been caught in a possum trap. Extensive monitoring shows kiwi are not at risk from the use of biodegradable 1080 poison.[29]