The kiwi bird is very curious: it cannot fly, it has loose, hair-like feathers, strong legs and no tail. The bird has many strange and wonderful features that have been shaped by the isolation of New Zealand and the absence of mammals on its territory. It is believed that the kiwi has evolved to take on a habitat and lifestyle that would be impossible in other parts of the world due to the presence of mammalian predators.
Origin of the species and description
The kiwi is a flightless bird that is in the genus Apteryx and the family Apterygidae. Its size is approximately the size of a domestic chicken. The genus name Apteryx comes from the ancient Greek for “no wing”. It is the smallest living ratite on Earth.
Comparison of the DNA sequence has led to the unexpected conclusion that kiwis are much more closely related to the extinct Malagasy elephant birds than to the moa with which they coexisted in New Zealand. In addition, they have much in common with emus and cassowaries.
Video: Kiwi bird
Research published in 2013 on the extinct genus Proapteryx, known from Miocene deposits, showed it to be smaller and likely to have the ability to fly, supporting the hypothesis that the kiwi bird’s ancestors reached New Zealand independently of the moa, which by the time kiwis appeared, were already large and wingless. Scientists believe that the ancestors of the current kiwi ended up in New Zealand traveling from Australasia about 30 million years ago, and maybe earlier.
Some linguists attribute the word kiwi to Numenius tahitiensis, a migratory bird that winters on tropical Pacific islands. With its long, curved beak and brown body, it resembles a kiwi. So when the first Polynesians arrived in New Zealand, they applied the word kiwi to the newly found bird.
Fun fact: The kiwi is recognized as the symbol of New Zealand. This association is so strong that the term Kiwi is used internationally.
The kiwi egg is one of the largest in terms of body size (up to 20% of the female’s weight). This is the highest rate of any bird species in the world. Other unique adaptations of the kiwi, such as their hair-like feathers, short and strong legs, and the use of their nostrils to detect prey before they even see it, have helped make this bird world famous.
Appearance and features
Their adaptation is extensive: like all other ratites (emus, rheas and cassowaries), their vestigial wings are extremely small, so that they are invisible under hairy, bristly feathers. While adults have bones with hollow interiors to minimize weight to make flight feasible, kiwis have mammal-like bone marrow.
Brown kiwi females carry and lay one egg, which can weigh up to 450 g. The beak is long, pliable and sensitive to touch. The kiwi has no tail, and the stomach is weak, the caecum is elongated and narrow. Kiwis rely little on sight for survival and foraging. Kiwi’s eyes are very small in relation to body mass, resulting in the smallest visual field of view. They are adapted for nocturnal life, but mainly rely on other senses (hearing, smell and somatosensory system).
Studies have shown that one third of the New Zealand livestock had lesions in one or both eyes. In the same experiment, three specific samples were observed that showed complete blindness. Scientists have found that they are in good physical condition. A 2018 study found that the kiwi’s closest relatives, the extinct elephant birds, also shared this trait despite their huge size. The temperature of the kiwi is 38°C, which is colder than other birds and closer to mammals.
Where does the kiwi live?
Kiwis are endemic to New Zealand. They live in evergreen damp forests. Elongated toes help the bird not to get stuck in marshy ground. In the most populated areas, there are 4-5 birds per 1 km².
By species, kiwis are distributed as follows:
- Large gray kiwi (A. haastii or Roroa) is the largest species, about 45 cm high and weighing about 3.3 kg (males about 2.4 kg) . Has gray-brown plumage with light stripes. The female lays only one egg, which is then incubated by both parents. Habitats are located in the mountainous regions of northwest Nelson, they can also be found on the northwest coast and in the southern Alps of New Zealand;
- Lesser Spotted Kiwi (A. owenii) These birds are unable to withstand predation by introduced pigs, stoats and cats, which has led to their extinction on the mainland. For 1350 years they have been living on the island of Kapiti. It was brought to other islands without predators. Obedient bird 25 cm high;
- Rowie or Okarito brown kiwi (A. rowi), first identified as a new species in 1994. Distribution is limited to a small area on the west coast of New Zealand’s South Island. Has a grayish plumage. Females lay up to three eggs per season, each in a separate nest. Male and female are incubated together;
- Southern brown or common kiwi (A. australis) Is a relatively common species. Its size is almost identical to that of the large spotted kiwi. Similar to the brown kiwi, but with lighter plumage. It lives on the coast of the South Island. Has several subtypes;
- Northern brown species (A. mantelli). Widely distributed over two-thirds of the North Island, with 35,000 remaining individuals, it is the most common kiwi. Females are about 40 cm tall and weigh about 2.8 kg, males — 2.2 kg. The brown color of the Northern Kiwi shows amazing resilience: it adapts to a wide range of habitats. The plumage is striped brownish-red and prickly. The female usually lays two eggs, which are incubated by the male.
What does the kiwi bird eat?
Kiwis are omnivores. Their stomach contains sand and small stones that aid in the digestion process. Because kiwis live in a variety of habitats, from mountain slopes to exotic pine forests, it’s difficult to pinpoint a typical kiwi diet.
Most of their food — invertebrates, and local worms that grow up to 0.5 meters are a favorite. Fortunately, New Zealand is rich in worms: there are 178 native and exotic species to choose from.
Besides this, kiwi is eaten:
- various seeds ;
- leaves of plants: species include podocarp totara, chinau and various coprosma and chebe.
The kiwi’s diet is closely related to their reproduction. Birds need to create large nutrient reserves in order to successfully complete the breeding season. Brown kiwis also feed on mushrooms and frogs. They are known to catch and eat freshwater fish. In captivity, one kiwi caught eels/tuna from a pond, immobilized them with a few blows, and ate them.
Kiwi can get all the water the body needs from food — succulent earthworms are 85% water. This adaptation means they can live in dry places like Kapiti Island. Being nocturnal also helps them adjust, as they don’t get overheated or dehydrated in the sun. When a kiwi bird drinks, it dips its beak, throws back its head and gurgles in the water.
Character and lifestyle features
Kiwi — nocturnal birds, as are many of New Zealand’s native animals. Their sound signals pierce the forest air at dusk and dawn. Kiwi’s nocturnal habits may be the result of predators entering the habitat, including humans. In protected areas where there are no predators, kiwis are often found in daylight. They prefer subtropical and temperate forests, but life circumstances force the birds to adapt to different habitats such as subalpine scrub, grasslands and mountains.
Kiwis have a highly developed sense of smell, unusual for a bird, and are the only birds with nostrils at the end of their long bills. Since their nostrils are located at the end of their long beaks, kiwis can detect insects and worms underground using their keen sense of smell without actually seeing or hearing them. The birds are very territorial, with razor-sharp claws that can cause some injury to an attacker. According to kiwi researcher Dr. John McLennan, one remarkable spotted kiwi in the Northwest region named Pete is notorious for using the “catapult to hit and run” principle. He jumps on your foot, pushes off, and then runs into the undergrowth.”
Kiwis have excellent memories and can remember unpleasant incidents for at least five years. During the day, the birds hide in a hollow, burrow or under the roots. The burrows of the great gray kiwi are labyrinths with multiple exits. On its site, the bird has up to 50 shelters. The kiwi populates in the hole after a few weeks, waiting for the entrance to be disguised by overgrown grass and moss. It happens that kiwi specially hide the nest, masking the entrance with twigs and leaves.
Social structure and reproduction
Male and female Kiwis live their entire lives as a monogamous couple. During the mating season, from June to March, the pair meet in the burrow once every three days. These relationships can last up to 20 years. They stand out from other birds in that they have a functioning pair of ovaries. (In many birds and the platypus, the right ovary never matures, so only the left one functions.) Kiwi eggs can weigh up to one-quarter that of the female. Usually only one egg is laid per season.
Fun fact: The kiwi lays one of the largest eggs in proportion to the size of any bird in the world, so even though the kiwi is the size of a domestic chicken, it can lay eggs that are about six times the size of a chicken egg.
Eggs are smooth and ivory or greenish white in color. The male incubates the egg, except for the great spotted kiwi,A. haastii, where incubatingboth parents are involved. The incubation period lasts approximately 63–92 days. The production of a huge egg places a significant physiological burden on the female. During the thirty days it takes to grow a fully developed egg, the female must eat three times her usual amount of food. Two or three days before egg-laying begins, there is little room for the stomach inside the female, and she is forced to fast.
Natural enemies of the kiwi bird
New Zealand is the land of birds , before the settlement of people on its territory, there were no warm-blooded predators-mammals. Now this is the main threat to the survival of kiwi, as introduced predators contribute to the death of eggs, chicks and adults.
The main culprits for the decline in the population are:
- ermines and cats, which cause great damage to young chicks during the first three months of their life;
- dogs prey on adult birds and this is bad for the kiwi population, because without them there are no eggs or chickens to maintain the population ;
- ferrets also kill adult kiwis;
- possums kill both adult kiwis and chicks, destroy eggs and steal kiwi nests;
- boars destroy eggs, and can also kill adult kiwis.
Other animal pests, such as hedgehogs, rodents, and weasels, may not kill kiwis, but they also cause problems. First, they compete for the same food as kiwis. Secondly, they are prey to the same animals that attack kiwis, helping to support large numbers of predators.
Interesting fact: Kiwi feathers have a specific smell, like a mushroom. This makes them extremely vulnerable to terrestrial predators that have originated in New Zealand, who easily detect these birds by scent.
In areas where kiwi predators are heavily controlled, kiwi hatching increases to 50 — 60%. A bird survival rate of 20% is required to maintain population levels, whatever exceeds it. Thus, control is of great importance, especially when dog owners keep them under control.
Population and species status
There are about 70,000 kiwis left in all of New Zealand. On average, 27 kiwis are killed by predators every week. This reduces the livestock by about 1400 kiwis every year (or 2%). At this rate, the kiwi may disappear in our lifetime. Just a hundred years ago, kiwis numbered in the millions. One stray dog can wipe out an entire kiwi population in a matter of days.
Approximately 20% of the kiwi population is in protected areas. In areas where predators are under control, 50-60% of chicks survive. Where areas are not uncontrolled, 95% of kiwis die before reaching breeding age. To increase the population, only 20% of the survival rate of chicks is enough. The proof of success is the population on the Coromandel, a predator-controlled zone where the number of individuals doubles every ten years.
Fun Fact: Risks to small kiwi populations include loss of genetic diversity, inbreeding, and vulnerability to localized natural events such as fires, disease, or increased predation.
Decreased chances of finding a mate in a declining, small population can also lead to lower reproductive rates. The Maori traditionally believe that the kiwi was under the protection of the god of the forest. Previously, birds were used for food, and feathers were used to make ceremonial cloaks. Now, although kiwi feathers are still used by the local population, they are collected from birds that die naturally, as a result of traffic accidents or due to predators. Kiwis are no longer hunted, and some Maori consider themselves bird guardians.
Kiwi bird protection
There are five recognized species of this animal, four of which are currently listed as vulnerable and one of which is endangered. All species have been adversely affected by historical deforestation, but the remaining large areas of their forested habitat are now well protected in nature reserves and national parks. Currently, the greatest threat to their survival is predation by invasive mammals.
Three species are listed in the international Red Book and have the status of Vulnerable (vulnerable), and a new species of Rowe or Okarito brown kiwi is endangered. In 2000, the Department of Conservation established five kiwi sanctuaries focused on developing and increasing kiwi conservation practices. The brown kiwi was introduced to Hawke Bay between 2008 and 2011, which in turn led to captive rearing of chicks that were released back into their native Maungatani forest.
Operation Nest Egg & #8212; it is a program to take kiwi eggs and chicks from the wild and hatch or raise them in captivity until the chicks are big enough to fend for themselves — usually when the weight reaches 1200 grams. After that, the kiwi bird is returned to the wild. Such chicks have a 65% chance of surviving to adulthood. Efforts to protect the kiwi bird have had some success in recent years, and in 2017 the IUCN removed two species from the endangered and vulnerable list.