Black robin | |
---|---|
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Aves |
Order: | Passeriformes |
Infraorder: | Passerides |
Family: | Petroicidae |
Genus: | Petroica |
Species: | P. traversi |
Binomial name | |
Petroica traversi (Buller, 1872) | |
Synonyms | |
Miro traversi |
The black robin or Chatham Island robin (Moriori: karure, Māori : kakaruia; Petroica traversi) is an endangered bird from the Chatham Islands off the east coast of New Zealand. It is closely related to the South Island robin (P. australis). It was first described by Walter Buller in 1872. The binomial commemorates the New Zealand botanist Henry H. Travers (1844–1928). Unlike its mainland counterparts, its flight capacity is somewhat reduced. Evolution in the absence of mammalian predators made it vulnerable to introduced species, such as cats and rats, and it became extinct on the main island of the Chatham group before 1871, being restricted to Little Mangere Island thereafter. [2]
The first mention of the black robin in science was at a presentation given by William Travers at the Wellington Philosophical Society in 1871. He presented the findings of his son, Henry Travers, who had visited the Chatham Islands to investigate their fauna. Although Henry Travers' notes on his visit were published the following year, it was the publication of Walter Buller a month later that is considered the species' official description. [3]
In 1905 it was believed to be completely vanished: "...the so-called black Tit or black Robin, Miro traversi, have fallen victims to man and his satellites." [4]
The black robin is a small, sparrow-sized bird measuring 10–15 centimetres (3.9–5.9 in). Its plumage is almost entirely brownish-black, with a black bill and brownish-black yellow-soled feet. [2]
Females are usually slightly smaller than males. Male songs are a simple phrase of 5 to 7 notes. Its call is a high-pitched single note. Their eyes are dark brown. Black robins moult between December and March.
Black robins live in low-altitude scrub forest remnants. They are entirely insectivorous, feeding on the forest floor or on low branches, and preferring to nest in hollow trees and tree stumps. To shelter from the strong winds and rough seas around the islands, they frequent the lower branches of the forest, or in flat areas with deep litter layers. They prefer woody vegetation under the canopies of trees such as akeake.
Black robins are territorial. Males will patrol and defend their areas. Females have been known to chase away other females. They make short flights from branch to branch and do not fly long distances.
Black robins forage in the leaf litter on the ground for grubs, cockroaches, wētā, and worms. Black robins will hunt for food during the day and night and have good night vision.
Black robins will generally start to breed at two years of age. The female robin will make the nest, and while she lays and incubates the eggs, the male will feed the female for a rest.
Eggs are laid between early October and late December. A second clutch may be laid if the first is unsuccessful. The clutch size varies from one to three eggs, but two is typical. Eggs are creamy in colour with purple splotches. When the eggs are laid, the female will sit on them to keep them warm until they hatch, after about 18 days. Then both parents will help to feed the chicks. Young robins stay in the nest for about 23 days after hatching, but even after leaving the nest the parents will continue to feed them until they are about 65 days old. This period of parental care is longer than would normally be expected for a bird of this size. After leaving the nest, chicks often spend the first day or two on the ground learning to use their wings, and here they are exposed to predators.
Survivorship between 1980 and 1991 indicates a mean life expectancy of four years. "Old Blue", the sole breeding female in 1980, lived for over 14 years. Some black robins can live from 6 to 13 years.
There are now around 300 black robins (in 2021), [5] but in 1980 only five survived on Little Mangere Island. They were saved from extinction by Don Merton and his Wildlife Service team, and by "Old Blue", the last remaining fertile female. The remaining birds were moved to Mangere Island. The team increased the annual output of Old Blue (and later other females) by removing the first clutch every year and placing the eggs in the nest of the Chatham race of the tomtit, a technique known as cross-fostering. The tomtits raised the first brood, and the black robins, having lost their eggs, relaid and raised another brood. [6]
Many females laid eggs on the rims of nests where the eggs could not survive without help. Human conservationists pushed the eggs back into the nests where they were incubated and hatched successfully. The maladaptive gene causing this behaviour spread until over 50% of females laid rim eggs. Humans stopped pushing eggs back in time to prevent the gene spreading to all birds which could have made the birds dependent on humans indefinitely. After human intervention stopped, rim laying became less frequent, but 9% of birds still laid rim eggs as of 2011. Conservationists have faced some criticism that they may inadvertently do harm, if they allow organisms with deleterious traits to survive and perpetuate what is maladaptive. [7]
All of the surviving black robins are descended from "Old Blue", giving little genetic variation among the population and creating the most extreme population bottleneck possible. However, this does not seem to have caused inbreeding problems, leading to speculation that the species has passed through several such population reductions in its evolutionary past, and has lost any alleles that could cause deleterious inbreeding effects. [8] [9] It was generally assumed that the minimum viable population protecting from inbreeding depression was around 50 individuals, but this is now known to be an inexact average, with the actual numbers being below 10 in rapidly reproducing small-island species, such as the black robin, to several hundred in long-lived continental species with a wide distribution (such as elephants or tigers). [10] [11]
Nest predation by introduced common starlings is the most common cause of nesting failure for black robins on Rangatira Island, with almost 21% of nests failing due to starlings. Incidents of failure caused by starlings are more common when black robins nest in cavities compared to open nests. [12]
The species is still vulnerable, but now numbers around 300 individuals in populations on Mangere Island and South East Island. Ongoing restoration of habitat and eradication of introduced predators is being undertaken, so that the population of this and other endangered Chatham endemics can be spread to several populations, decreasing the risk of extinction by natural disasters or similar stochastic events. Attempts made to establish another population in a fenced covenant on Pitt Island have failed so far. [5]
The South Island robin is a sparrow-sized bird found only in New Zealand, where it has the status of a protected endemic species. The birds are sparsely distributed through the South Island and Stewart Island / Rakiura, although the distribution is not continuous. The nominate, and the Stewart Island robin are the two subspecies. The species is closely related to the North Island robin, and also to the extremely rare black robin of the Chatham Islands.
Conservation in New Zealand has a history associated with both Māori and Europeans. Both groups of people caused a loss of species and both altered their behaviour to a degree after realising their effect on indigenous flora and fauna.
Donald Vincent Merton was a New Zealand conservationist best known for saving the black robin from extinction. He also discovered the lek breeding system of the kākāpō.
The Chatham oystercatcher or Chatham Island oystercatcher is a species of oystercatcher. It is a wading bird endemic to the Chatham Islands, New Zealand. This species is rated by the IUCN as endangered, and has a current population of 310 to 325 birds. The main threat is from introduced predators.
Captive breeding, also known as captive propagation, is the process of keeping plants or animals in controlled environments, such as wildlife reserves, zoos, botanic gardens, and other conservation facilities. It is sometimes employed to help species that are being threatened by the effects of human activities such as climate change, habitat loss, fragmentation, overhunting or fishing, pollution, predation, disease, and parasitism.
The Mauritius kestrel is a bird of prey from the family Falconidae endemic to the forests of Mauritius, where it is restricted to the southwestern plateau's forests, cliffs, and ravines. It is the most distinct of the Indian Ocean kestrels. It colonized its island home to evolve into a distinct species probably during the Gelasian . It is the most distant living species among the western Indian Ocean kestrels.
The tomtit is a small passerine bird in the family Petroicidae, the Australasian robins. It is endemic to the islands of New Zealand, ranging across the main islands as well as several of the outlying islands. In the Māori language, the North Island tomtit is known as miromiro and the South Island tomtit is known as ngirungiru. This bird has several other Māori and English names as well. There are several subspecies showing considerable variation in plumage and size. The species is not threatened and has adapted to the changes made to New Zealand's biodiversity.
The Chatham parakeet, also known as Forbes' parakeet, is a rare parakeet endemic to the Chatham Islands group, New Zealand. This parakeet is one of New Zealand's rarest birds and is classified as Vulnerable on the IUCN Red List, as a result of a range of threats to the species survival, including habitat loss, predation, and hybridization. A number of conservation methods have been employed to assist the recovery of this species, and currently the population trend is considered stable.
The red-capped robin is a small passerine bird native to Australia. Found in drier regions across much of the continent, it inhabits scrub and open woodland. Like many brightly coloured robins of the family Petroicidae, it is sexually dimorphic. Measuring 10.5–12.5 cm (4.1–4.9 in) in length, the robin has a small, thin, black bill, and dark brown eyes and legs. The male has a distinctive red cap and red breast, black upperparts, and a black tail with white tips. The underparts and shoulders are white. The female is an undistinguished grey-brown. This species uses a variety of songs, and males generally sing to advertise territories and attract females. Birds are encountered in pairs or small groups, but the social behaviour has been little studied.
The Chatham gerygone or Chatham Island warbler is a species of bird in the family Acanthizidae. It is endemic to the Chatham Islands. The Chatham Island warbler is larger than and differs in plumage from the related grey warbler of mainland New Zealand. Both warblers were discovered and named by G. R. Gray in 1845. The grey and Chatham Island warblers are the only two members of the Australasian family Acanthizidae found in New Zealand.
The hooded robin is a small passerine bird native to Australia. Like many brightly coloured robins of the Petroicidae, it is sexually dimorphic; the male bears a distinctive black-and-white plumage, while the female is a nondescript grey-brown.
The pink robin is a small passerine bird native to southeastern Australia. Its natural habitats are cool temperate forests of far southeastern Australia. Like many brightly coloured robins of the family Petroicidae, it is sexually dimorphic. Measuring 13.5 cm (5.3 in) in length, the robin has a small, thin, black bill, and dark brown eyes and legs. The male has a distinctive white forehead spot and pink breast, with grey-black upperparts, wings and tail. The belly is white. The female has grey-brown plumage. The position of the pink robin and its Australian relatives on the passerine family tree is unclear; the Petroicidae are not closely related to either the European or American robins, but appear to be an early offshoot of the Passerida group of songbirds.
The rose robin is a small passerine bird native to Australia. Like many brightly coloured robins of the Petroicidae, it is sexually dimorphic. The male has a distinctive pink breast. Its upperparts are dark grey with white frons, and its tail black with white tips. The underparts and shoulder are white. The female is an undistinguished grey-brown. The robin has a small black bill and eyes.
The Pitt shag, also known as the Pitt Island shag or Featherstone's shag, is a species of bird in the family Phalacrocoracidae. It is endemic to Pitt Island where its natural habitats are open seas and rocky shores. The bird with the color of a dark body, gray chest, yellow eyes and feet can be found in small groups in their breeding habitat or alone within 18 km from their territory searching for food. The species was close to extinction in 1905 but actions of conservation have been done ever since. The Pitt shag is threatened by habitat loss due to predation and climate change causing a decline from 1997 to 2012, but there is a recovery plan by the Department of Conservation.
The North Island robin is a species of Australasian robin endemic to the North Island of New Zealand. It and the South Island robin of the South Island and Stewart Island were once considered conspecific, but mitochondrial DNA sequences have shown that the two lineages split prior to the Pleistocene, and support the classification as two different species.
The Pacific robin, is a red-breasted Australasian robin in the passerine bird genus Petroica found in Melanesia and Polynesia. It is similar in plumage to the scarlet robin of Australia, and until recently the two were considered conspecific until split in 1999 by Schodde and Mason. Thirteen subspecies of Pacific robin are currently recognised, and these subspecies display considerable variation in plumage, foraging preferences, and habitat. The Norfolk robin was previously considered a subspecies of the Pacific robin, but is now considered a distinct species.
The Norfolk robin, also known as the Norfolk Island scarlet robin or Norfolk Island robin, is a small bird in the Australasian robin family Petroicidae. It is endemic to Norfolk Island, an Australian territory in the Tasman Sea, between Australia and New Zealand.
The Chatham tomtit is a subspecies of tomtit found on some of the smaller islands of New Zealand. It is most similar in plumage to the South Island tomtit, the nominate subspecies. The New Zealand government is implementing a plan to help this species and other bird species recover. The holotype is in the collection of the Museum of New Zealand Te Papa Tongarewa.
Old Blue was a Chatham Island robin who at one time was the only fertile female of the species left, and who has been credited with being the saviour of her species. She lived for approximately 13 years.
Attenborough, D. 1998. The Life of Birds. BBC ISBN 0563-38792-0