Takahē
| Takahē | |
|---|---|
 | |
| On Tiritiri Matangi Island. | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Gruiformes |
| Family: | Rallidae |
| Genus: | Porphyrio |
| Species: | P. hochstetteri |
| Binomial name | |
| Porphyrio hochstetteri (A. B. Meyer, 1883) | |
| Synonyms | |
|
Notornis mantelli Mantell, 1847 | |
The takahē, Notornis, or South Island takahē (Porphyrio hochstetteri) is a flightless bird indigenous to New Zealand and belonging to the rail family. It was thought to be extinct after the last four known specimens were taken in 1898. However, after a carefully planned search effort the bird was rediscovered by Geoffrey Orbell near Lake Te Anau in the Murchison Mountains, South Island, on 20 November 1948. The specific scientific name commemorates the Austrian geologist Ferdinand von Hochstetter.
Taxonomy and systematics
A related species, the North Island takahē (P. mantelli) or mōho is extinct and only known from skeletal remains. Both forms were long assumed to be subspecies of mantelli, and were usually placed in the genus Notornis. However, it has been determined that the differences between Porphyrio and Notornis were insufficient for separating the latter, whereas the differences between the North and South Island forms justified the splitting into two species, as each evolved independently towards flightlessness.[2]
Description
The takahē is the largest living member of the family Rallidae. Its overall length averages 63 cm (25 in) and its average weight is about 2.7 kg (6.0 lb) in males and 2.3 kg (5.1 lb) in females, ranging from 1.8–4.2 kg (4.0–9.3 lb).[3] The standing height is around 50 cm (20 in).[4] It is a stocky bird, with reduced wings, strong legs and a massive bill.
The adult takahē is mainly purple-blue in colour, with a greenish back and inner wings. It has a red frontal shield and red-based pink bill. The legs are pink. Sexes are similar, the females being slightly smaller, but young birds have mainly pale brown plumage. Immatures have a pinkish bill with bluish cast. This is a noisy species with a loud clowp call. The contact call is easily confused with that of the weka (Gallirallus australis), but is generally more resonant and deeper.[5]
Distribution and habitat
The species is still present in the location where it was rediscovered in the Murchison Mountains. Small numbers have also been successfully translocated to five predator-free offshore islands, Tiritiri Matangi, Kapiti, Maud, Mana and Motutapu, where they can be viewed by the public. Additionally, captive takahē can be viewed at Te Anau and Mt Bruce wildlife centres. In June 2006 a pair of takahē were relocated to the Maungatautari Restoration Project. In September 2010 a pair of takahē (Hamilton and Guy) were released at Willowbank Wildlife Reserve - the first non-Department of Conservation institution to hold this species. In January 2011 two takahē were released in Zealandia, Wellington, and in mid-2015, two more takahē were released on Rotoroa Island in the Hauraki Gulf. There have also been relocations onto the Tawharanui Peninsula.In 2014 two pair of Takahe were released into Wairakei golf and sanctuary, a private fenced sanctuary at Wairakei north of Taupo, the first chick was born there in November 2015 At the beginning of 2013 there were 263 takahē accounted for, showing slow but steady growth over the previous few years.
Behaviour and ecology
The takahē is a sedentary and flightless bird currently found in alpine grasslands habitats. Although it is indigenous to swamps, humans turned its swampland habitats into farmland, and the takahē was forced to move upland into the grasslands. It holds territories in the grassland until the arrival of snow, when it descends to the forest or scrub. It eats grass, shoots and insects, but predominantly leaves of Chionochloa tussocks and other alpine grass species. The takahē can often be seen to pluck a snow grass (Danthonia flavescens) stalk, taking it into one claw and eating only the soft lower parts which is a favourite food. The rest is discarded. A takahē has been recorded feeding on a paradise duckling at Zealandia. Although this behaviour was previously unknown, the related pukeko occasionally feeds on eggs and nestlings of other birds as well.
Breeding
The takahē is monogamous (with pairs remaining from 12 years to, probably, their entire lives), builds a bulky nest under bushes and scrub, and lays one to three buff eggs. It is territorial. The chick survival rate is 73-97%. Recently, human intervention has been required to maintain the breeding the success of the takahē. For the success of fledgling takahē is relatively low in the wild compared to other, less threatened species, so methods such as the removal of infertile eggs from nests and the captive rearing of chicks have been introduced to manage the takahē population. The Fiordland takahē population has a successful degree of reproductive output due to these management methods: the number of chicks per pairing with infertile egg removal and captive rearing is 0.66, compared to 0.43 for regions without any breeding management.
Status and conservation
The near-extinction of the formerly widespread takahē is due to a number of factors: over-hunting, loss of habitat and introduced predators have all played a part. The introduction of red deer (Cervus elaphus) represent a severe competition for food, while the stoats (Mustela erminea) take a role as predators. The spread of the forests in post-glacial Pleistocene-Holocene has contributed to the reduction of habitat. Since the species is long-lived, reproduces slowly, takes several years to reach maturity, and had a large range that has drastically contracted in comparatively few generations, inbreeding depression is a significant problem. The recovery efforts are hampered especially by low fertility of the remaining birds. Genetic analyses have been employed to select captive breeding stock in an effort to preserve the maximum genetic diversity.[6]
Decline of takahē
Takahē were assumed to be extinct but were rediscovered by Geoffrey Orbell near Lake Te Anau in the Murchison Mountains, South Island, New Zealand on 20 November 1948. Takahē were at one time present throughout this island country, but for several reasons ceased to be found, which made many think that they were wiped out. Many reasons were cited for the failure of this flightless bird. There are two significant periods when takahē numbers declined: Pre-European and Post-European arrival.
Reasons for the pre-European decline of takahē were postulated by Williams (1962) and later supported in a detailed report by Mills et al. (1984).[7][8] They held that climate changes were the main cause of the failure in takahē before European settlement. The environmental variations before the European settlement were not suitable for takahē, and exterminated almost all of them. Survival in the altering temperature was not tolerable by this group of birds. Takahē live in alpine grasslands, but the post-glacial era destroyed those zones which caused an intense decline in their numbers.
Secondly, they suggested that Polynesian settlers arriving about 800–1000 years ago, bringing dogs and Polynesian rats and hunting takahē for food, started another decline. European settlement in the nineteenth century almost wiped them out through hunting and introducing mammals such as deer which competed for food and predators (e.g. stoats) which preyed on them directly.
Takahē population, conservation and protection
After long threats of extinction, takahē now find protection in the Fiordland National park (New Zealand’s largest national park). However, the species have not made a stable recovery in this habitat since they were rediscovered in 1948. In fact the takahē population was at 400 before it was reduced to 118 in 1982 due to competition with Fiordland domestic deer. Conservationists noticed the threat deer posed to takahē survival and the national park now implements deer control by hunting by helicopter.
The rediscovery of the takahē caused great public interest in which the New Zealand government took immediate action in closing off a remote part of the Fiordland National Park to prevent the bird from being bothered. However, since the moment of rediscovery, there were different perspectives on how the bird should be conserved. According to the Forest and Bird Society, takahēs should be left to work out their own “destiny”. However, this viewpoint caused many to worry that the takahē would be incapable of making a comeback and thus become extinct like New Zealand’s native huia bird population. Interventionists then sought to relocate the takahē “island sanctuaries” and breed them in captivity. However, no action was taken for nearly a decade due to a lack of resources and the will to avoid conflict. Fortunately, biologists from the Department of Conservation utilized their experience of designing remote island sanctuaries to establish a safe habitat for the takahē on Maud Island in the Malborough Sounds, Mana, and Kapiti Island north of Wellington off the Wairarapa Coast, and Tiritiri Matangi Island in the Hauraki Gulf. When such conservation strategies such as translocation of a species to island sanctuaries are successful, populations generally reach their carrying capacity rather quickly which can subsequently generate numerous issues with productivity and “population growth rates associated with density-dependent effects as well as increased rates of inbreeding. “ Scientists discovered through the use of logistic regression and generalized linear models that the takahē island metapopulation appears to have indeed reached carrying capacity as revealed by the increasing ratio of non-breeding to breeding adults, and declines in produced offspring. Such results pose problems regarding the maintenance of genetic diversity and thus takahē survival in the long term. Thus increasing translocation rates of takahē from the New Zealand mainland onto island sanctuaries may not be effective unless “surplus birds are removed”.
Future efforts for protection
The original recovery strategies and goals set in the early 1980s, both long-term and short-term, are now well under way.
The programme to move takahē to predator-free island refuges, where the birds also receive supplementary feeding, began in 1984. Takahē can now be found on 5 small islands; Maud Island (Marlborough Sounds), Mana Island (off Wellington's west coast), Kapiti Island (off Wellington's west coast), Tiritiri Matangi Island (Hauraki Gulf) and Motutapu Island (Hauraki Gulf). The Department of Conservation also runs a captive breeding and rearing programme at the Burwood Breeding Centre near Te Anau which consists of 5 breeding pairs. Chicks are reared with minimal human contact, being fed and brooded through the use of puppets and models. The offspring of the captive birds are used for new island releases and to add to the wild population in the Murchison Mountains. The Department of Conservation also manages wild takahē nests to boost the birds' recovery. Surplus eggs from wild nests are taken to the Burwood Breeding Centre.
An important management development has been the stringent control of deer in the Murchison Mountains and other takahē areas of Fiordland National Park. Following the introduction of deer hunting by helicopter, deer numbers have decreased dramatically and alpine vegetation is now recovering from years of heavy browsing. This improvement in its habitat has helped to increase takahē breeding success and survival. Current research aims to measure the impact of attacks by stoats and thus decide whether stoats are a significant problem requiring management.
One of the original long-term goals was to establish a self-sustaining population of well over 500 takahē. The population stood at 263 at the beginning of 2013.
References
- ↑ BirdLife International (2013). "Porphyrio hochstetteri". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013.
- ↑ Trewick, S.A. & Worthy, T.H. (2001) Origins and prehistoric ecology of takahe based on morphometric, molecular, and fossil data. In: Lee, W.G.; Jamieson, I.G. (ed.), The Takahe: 50 years of conservation management and research, pp. 31-48. Otago University Press, Dunedin, New Zealand.
- ↑ UNEP-WCMC Species Page (April 2008)
- ↑ Taylor, Barry, Rails: A Guide to the Rails, Crakes, Gallinules and Coots of the World. Yale University Press (1998), ISBN 978-0-300-07758-2.
- ↑ del Hoyo, J. Elliott, A. & Sargatal, J. (editors). (1996) Handbook of the Birds of the World. Volume 3: Hoatzin to Auks. Lynx Edicions. ISBN 84-87334-20-2
- ↑ BirdLife International 2009. Species factsheet: Porphyrio hochstetteri. Downloaded on 1 December 2009.
- ↑ Williams, G.R. (1962) The Takahe (Notornis mantelli Owen 1848); a general survey. Trans. Royal Soc. New Zealand 88:235-258.
- ↑ Mills, J.A. Lavers, R.B. & Lee, W.G. (1984) The Takahe: A relict of the Pleistocene grassland avifauna of New Zealand. New Zealand Journal of Ecology 7:57-70.
External links
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Wikimedia Commons has media related to Porphyrio hochstetteri. |
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Wikispecies has information related to: Porphyrio hochstetteri |
- Takahē videos on the Internet Bird Collection
- Takahē Educational Worksheet for Kids on EasyScienceforKids.
- The Official Takahē Recovery Website
