Dwarf kiwi
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Dwarf kiwi ( Apteryx owenii ) |
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| Apteryx owenii | ||||||||||||
| Gould , 1847 |
The dwarf kiwi ( Apteryx owenii ), also known as the small spot kiwi , is the smallest type of kiwi fruit . As the rarest of the five kiwi species, the dwarf kiwi has been wiped out on both of New Zealand's main islands. Even the Māori made sure that it disappeared from the North Island before the arrival of the whites , the last sighting on the South Island took place in 1938. Today the main distribution of the dwarf kiwi are five islands off the New Zealand coasts, on which it was deliberately introduced by humans in order to survive Kind of secure: Kapiti Island , Red Mercury Island, Hen Island, Tiritiri Matangi and Long Island. These protective measures have already had an effect: The dwarf kiwi is the only kiwi species whose population is growing.
Due to the goals achieved in the preservation of the population, the IUCN only lists the dwarf kiwi on the warning list near threatened and estimates the population at a total of 1,200 sexually mature individuals.
Appearance
The dwarf kiwi reaches a body length of 35 to 45 centimeters. The body height is 25 centimeters. Young birds do not reach the size of adult birds until they are around 18 months old. The sexual dimorphism is not very pronounced. Females are generally a little heavier and larger than males. What is striking, however, is the difference in the length of the beak: the beak of the males is 6.8 centimeters long, while that of the females is 8.5 centimeters.
Dwarf kiwis have the hair-like plumage typical of kiwis. It is gray-brown to grayish with small pale spots or tiny lighter strands. A tail is missing, which leads to the oval, pear-shaped body shape. The beak is narrow and slightly curved and makes up about 20 percent of the total length. Legs and feet are strongly developed. Three of the four toes point forward and have strong claws, the fourth, which is slightly less developed, points backwards.
Dwarf kiwis only weigh about half the weight of other kiwi species, but are otherwise similar in shape and plumage. The striped kiwi has a slightly brown plumage with darker vertical stripes. There is a possibility of confusion with the Haastkiwi , from which it can only be distinguished during field observations on the basis of body size.
distribution and habitat
The dwarf kiwi is endemic to New Zealand, which was originally widespread across the entire South and North Island of New Zealand and was probably also found on some islands off the New Zealand coast. Some authors suspect that Kapiti Island, where it still occurs today, was part of the original natural range. BirdLife International , however, takes the view that Kapiti Island has only been inhabited by dwarf kiwis since a targeted settlement at the beginning of the 20th century. On the 20 square kilometers of Kapiti Island, the species has probably now reached population density. However, the proportion of young birds and the rate of reproduction are still high here. The dwarf kiwi was settled on another three islands in the 1980s and also on Tiritiri Matangi between 1993 and 1995. However, all of these islands are much smaller than Kapiti Island, and a much smaller population lives on them. It was reintroduced at the Karori Wildlife Sanctuary , an area of 225 hectares near Wellington where a special fence prevents introduced mammals from entering.
The dwarf kiwi habitat is evergreen forests with dense undergrowth and the transition zone to grassland in the temperate climate zone. Its height distribution ranges from sea level to altitudes of at least 1000 meters. It tolerates a temperature range from slightly minus degrees to 25 ° C. The average annual rainfall is 1000 millimeters, but it used to populate regions in which up to 6800 milliliters fell. In the last few decades it has predominantly been found in hilly regions; it probably also inhabited mountain regions and lowlands in the past. Early European reports on the dwarf kiwi reported its occurrence in damp forests with moss-covered soil and numerous rotting dead wood . There it rested and nested in hollow trees, in naturally occurring caves between the roots of large trees and in crevices in the rock. In general, he prefers hillside locations as immediate action areas. The territory of adult birds is between two and three hectares . Dwarf kiwis are resident birds that presumably occupy their territory for life. So far, no information is available on the migration of young birds.
Food and subsistence
Dwarf kiwis are omnivores, but they mainly eat ground-dwelling invertebrates such as earthworms, millipedes , beetles, beetle larvae, moths and flies in the larval stage, spiders and some fruits. The food is found by poking the ground with the beak. Individual pieces of food are grasped with the beak in a tweezer-like grip and thrown by a backward movement of the head into the area of the beak to which the tip of the tongue extends. Kiwis will likely hear and smell their prey. They mainly look for their food during the night, but young birds are also active at dusk. Unlike the adult birds, the young birds can initially only poke up to 50 millimeters in the ground. The examination of their droppings has shown that they have a similar food spectrum as the adults, but rather eat smaller prey.
Reproduction
Dwarf kiwis enter into a monogamous couple relationship that presumably lasts until one of the two partner birds dies. Pair bonds are presumably established from the age of two. The territory that a couple occupies is defended against intruders. Area behavior includes calls that can be heard all year round. Antagonistic behavior towards intruders includes approaching him, which is accompanied by snorting noises. If none of the birds withdraws, fights can ensue, in which the animals kick one another, among other things. It is not yet known how long offspring will be tolerated in the area. According to available information, however, the young birds seem to leave the territory of the parent birds in their first year of life.
Dwarf kiwis can probably breed all year round, on Kapiti Island the breeding season fell mainly in the months of September and October. Females have been observed to visit the place where the young bird will later be raised up to two months before laying eggs. However, no information is available on how a pair of kiwis choose their nesting site. Kiwis are cave-breeders that breed in earthworks, tree hollows or other natural caves they have dug. Of 31 nests on Kapiti Island, 22 were in earthworks dug by the kiwis themselves. Three nests were in dense vegetation on the ground and two in caves at the foot of trees. Earthworks can be between 20 and 200 centimeters long. They have a diameter of 9 to 15 centimeters. The actual brood chamber is not enlarged. They dig new earthworks both for the next clutch and for the clutch of the next breeding season. The brood chamber is occasionally covered with twigs and dead leaves, and occasionally feathers are also found. The nesting material in the vicinity of the nesting site is apparently only sought by the male and carried to the nest location. What part the female has in nest building is not yet known.
The clutch consists of one or two eggs. The laying distance to the second egg is two to three weeks; however, this observation has so far only been made in captive birds. Only the male breeds, the female stays close to the nest at the time of hatching, but only the male takes care of the nestling. Young birds return to the nest location up to 26 days after they fledged. So far it has not been observed that the adult birds feed the young.
supporting documents
literature
- Josep del Hoyo et al .: Handbook of the Birds of the World. Volume 1: Ostrich to Ducks. Lynx Edicions, 1992, ISBN 8487334105 .
- PJ Higgins (Ed.): Handbook of Australian, New Zealand & Antarctic Birds. Volume 1: Ratites to Ducks. Oxford University Press, Oxford 1990, ISBN 0195530683 .
Web links
- Apteryx owenii inthe IUCN 2013 Red List of Threatened Species . Listed by: BirdLife International, 2012. Retrieved September 2, 2013.
- Avibase: Miniature Kiwi
- BirdLife factsheet about the dwarf kiwi
Single receipts
- ↑ BirdLife Factsheet on the Miniature Kiwi , accessed on May 29, 2011
- ↑ Higgins, p. 80
- ↑ Higgins, pp. 80-81
- ↑ Higgins, p. 81
- ↑ BirdLife Factsheet on the Miniature Kiwi , accessed on May 29, 2011
- ↑ Higgins, p. 81
- ↑ Higgins, p. 82
- ↑ Higgins, p. 82
- ↑ Higgins, p. 82
- ^ Higgins, p. 82 and p. 83
- ^ Higgins, p. 83
- ^ Higgins, p. 83
- ^ Higgins, p. 84
- ^ Higgins, p. 84
- ^ Higgins, p. 84