Brown Kiwi
Tagged: animal, animals, bird, cat, dog, insect, invertebrate, mammalApteryx mantelli
The mainland populations of the unique brown kiwi found only in New Zealand-have suffered huge declines in the 20th century, mainly due to plundering by introduced predators. With its shaggy, hairlike plumage, a plump, round body, a lack of visible tail or wings, and an ability to track down food in the dead of night, kiwis resemble nocturnal mammals rather than typical birds. Like many mammals, they also rest and shelter their young in burrows and mark their boundaries with strong-smelling droppings; the bristly modified feathers at the base of the bill serve as whiskers for feeling in the dark. Isolated for millions of years on New Zealand-where there are no native mammals except bats-the brown kiwi has occupied a niche that elsewhere would be filled by a mammal. Kiwis are the smallest living ratites-a group of flightless birds that includes the ostrich, rheas, cassowaries, and the emu, none of which are nocturnal. Until recently ornithologists recognized three species of kiwi: the little spotted kiwi, the brown kiwi, and the great spotted kiwi. Genetic research has led to the brown kiwi being split into two distinct species, the brown kiwi and the tokoeka of a few areas in South Island. The Maori name kiwi comes from the shrill call of males, which punctuates the night, especially during the breeding season.
Long-Term Decline
Brown kiwis were once widespread throughout North Island and the northern part of South Island. Although they were hunted by the Maori-who had colonized New Zealand from the Pacific by the 12th century this probably had little effect on overall numbers. It was not until the European settlers arrived in the mid 19th century that persecution of the birds began in earnest, as hunters tried to satisfy the demand for kiwi plumage by the clothing trade. A law banning the hunting, capture, or killing of kiwis was passed in 1908, but the pace of land clearance for agriculture and settlements destroyed much of the kiwi’s forest habitat. The birds’ fate was further sealed by the introduction of predatory mammals such as cats, dogs, and stoats. As a result of the combined threats, large scale losses of brown kiwis occurred. Researchers think that numbers of brown kiwis have fallen by at least 90 percent over the last 100 years and continue to decline at about 6 percent every year (in studied sites).
This represents the halving of the population each decade. However, the species’ overall decline is probably below 80 percent, thanks to the stability of the populations introduced to islands where predators are removed-and also to effective predator control in mainland sites. The main threat facing the brown kiwi is still introduced predators, especially since it evolved with no native predators. At least 94 percent of kiwi chicks die before they reach breeding age (about 14 months for males and two years for females). Half of this mortality is due to predation. The other main cause of decline is the clearance of native forest, which threatens small, isolated populations. Many kiwis also used to die in traps set to catch predators or possums; animals reached plague proportions in some areas. Today this is avoided by raising traps above the ground so that the kiwis do not stumble upon them.
Conservation
Conservationists have an accurate picture of kiwi populations thanks to an intensive, nationally coordinated program of monitoring. By culling introduced predators and by removing eggs and hand-rearing the young to an age when they can fend off attacks, key populations have been helped. Continued protection is needed to save the brown kiwi.
DATA PANEL
Brown kiwi
Apteryx mantelli
- Family: Apterygidae
- World population: About 35,000 birds
- Distribution: North Island in Northland; Coromandel Peninsula from Gisborne to northern Ruahine Range, and Tongariro to Taranaki. Introduced to Little Barrier, Kawau, and Pounui Islands. Isolated population on Okarito, South Island, may be a separate species with Critical status
- Habitat: Subtropical and temperate forests; regenerating forest, shrubland, pine plantations, and pastureland
- Size: Length: 16 in (40 cm) Weight: male 3-6.5 lb (1.4-3 kg); female 4.5-8 lb (2-3.8 kg)
- Form: Bird the size of a small dog; small head; long, slightly downcurved bill with bristles at base; long neck (usually drawn in); rotund body covered with coarse, hairlike plumage that is dark gray-brown with red-brown streaks; rudimentary wing stubs in plumage; strong legs; 4 toes on each foot
- Diet: Invertebrates in soil and leaf litter, especially earthworms, spiders, and insects; also fruit, seeds, and leaves
- Breeding: Female lays 1 or 2 very large eggs in August-September in burrow or natural cavity; egg(s) incubated by male for 11-12 weeks, chick(s) independent at 14-20 days; fully grown by 20 months
- Related endangered species: Great spotted kiwi (Apteryx haastii); little spotted kiwi (A. owenii); tokoeka (A. australis)
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