Black stilt

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Black stilt
Black Stilt 0A2A2243.jpg
Wild kakī in Lake Tekapo
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Charadriiformes
Family: Recurvirostridae
Genus: Himantopus
Species:
H. novaezelandiae
Binomial name
Himantopus novaezelandiae
Gould, 1841

The black stilt (Himantopus novaezelandiae) or kakī (Māori) is a wading bird found in New Zealand. It is one of the world's rarest birds, with 169 adults surviving in the wild as of May 2020. Adult kakī have distinctive black plumage, long pink legs, and a long thin black bill. Black stilts largely breed in the Mackenzie Basin in the South Island, and are threatened by introduced feral cats, ferrets, and hedgehogs as well as habitat degradation from hydroelectric dams, agriculture, and invasive weeds.

Contents

Taxonomy and systematics

Black stilts are one of several species in the genus Himantopus, classified along with avocets in the family Recurvirostridae. Although genetically and behaviourally distinct from pied stilts (Himantopus himantopus), they are able to successfully hybridise with them. Hybridisation and dilution of the gene pool is one reason black stilts are threatened with extinction. [2] Black and pied stilts in New Zealand represent two colonisations of pied stilt ancestors from Australia: the first, long ago, giving rise to melanistic descendants, the second in the early 19th century. [2]

Black stilt (Himantopus novaezealandiae), compared with the closely related pied stilt (H. himantopus). Painted by John Gould. Gouldaustilg.jpg
Black stilt (Himantopus novaezealandiae), compared with the closely related pied stilt (H. himantopus). Painted by John Gould.

Description

Black stilts are a medium-sized (220 g) wader with extremely long pink legs, red eyes, distinctively black plumage, and a long slender black bill. Juveniles have a white breast, neck and head, with a black patch around the eyes, and black belly feathers that distinguish them from pied stilts. [3] Black adult plumage appears in their first or second year. Black plumage may be an adaptation to "absorb heat better in the cold, windswept habitat of glacial riverbeds and lakeshores". [4]

Hybrids between black and pied stilts are very variable in their plumage, but usually have black breast feathers, which pied stilts never do.

Distribution and habitat

Although black stilts currently breed only in braided river systems in the South Island, subfossil bones show that prior to human arrival they were found in habitats as diverse as narrow bush streams in Hawkes Bay, and a wetland lake surrounded by forest in North Canterbury. [4] In the nineteenth century they bred on riverbeds and in wetlands of the central and eastern North Island and most of the South Island except Fiordland. As late as the 1940s they were still common in South Canterbury and Central Otago, [3] and nesting occurred in Central Otago as late as 1964. [2] Throughout their range they have been almost entirely replaced by pied stilts, which colonised New Zealand after human settlement and now number approximately 30,000. [4]

Currently black stilts breed only in the upper Waitaki River system in the Mackenzie Basin. Most black stilts will also overwinter in the Mackenzie Basin, but about 10% of the population, especially hybrids and those paired with pied stilts, migrate to North Island harbours such as Kawhia and Kaipara in January for the winter. [2] [3]

Behaviour and ecology

Breeding

Kaki nest in the Mackenzie Basin. Kaki, black stilt, nest.jpg
Kakī nest in the Mackenzie Basin.
External videos
Nuvola apps kaboodle.svg The Black Stilt
(Short documentary showing breeding and predators)

Black stilts breed at 2 (more usually 3) years of age. They nest as solitary pairs, not in a protective colony like pied stilts. [4] Both birds collaborate on building a nest in July or August on stable islands or banks in a shingle riverbed; pairs tend to nest in the same site each year. [2] Three to five eggs are laid from September to December, peaking in October, and are incubated for roughly 25 days. Chicks take six to eight weeks to fledge, [3] and remain with their parents for a further six to eight months. [2]

Conservation

Black stilt near Twizel Black Stilt DOC.jpg
Black stilt near Twizel
Pied stilt (Himantopus leucocephalus) on nest Pied Stilt on nest.jpg
Pied stilt (Himantopus leucocephalus) on nest
Hybrid (black x pied) stilt, showing node F plumage. (Hybrid black stilt colour patterns are described as 'nodes', ranging from 'A', closest to a pied stilt, to 'J', closest to a black stilt.) Hybrid Stilt DOC.jpg
Hybrid (black × pied) stilt, showing node F plumage. (Hybrid black stilt colour patterns are described as 'nodes', ranging from 'A', closest to a pied stilt, to 'J', closest to a black stilt.)

Despite decades of intensive protection, the black stilt remains one of the rarest species of wading bird, and one of the most endangered birds in the world. The population may have numbered 500–1000 birds in the 1940s, [5] but began to rapidly decline in the 1950s, and just 68 adults were counted in 1962. [2] Intensive management began in 1981, when numbers had declined to just 23 adult birds. [5] [6] By 1984, there were 32 adults in the wild, rising to 52 by 1992 (with another 32 in captivity). [2] As of May 2020 the wild population was estimated at 169 wild adult birds.

A captive population of kakī is maintained for breeding and subsequent wild release at a rearing facility in Twizel maintained by the Department of Conservation (DOC), and at the Isaac Conservation and Wildlife Trust in Christchurch. [7] [8] [9] Eggs are collected every year for rearing, from both wild and captive birds. 2021 was the second-best year on record for breeding, with 39 breeding pairs; 175 eggs were collected and 66 left to hatch on nests. [9] Each year juvenile captive-bred birds are released into the wild along the Godley, Cass, and Tasman rivers in Te Manahuna/Mackenzie Basin, in August or September; 130 in 2019, [10] over 150 in 2021 and 143 in 2023. [11] [12] The annual release in the wild of captive-bred birds, combined with predator control, have probably prevented black stilt from becoming extinct. [5]

Predators

Predation from mammalian invasive species poses the greatest threat to the survival of the species. In the 19th century, mustelids such as stoats, ferrets and weasels, as well as cats, were released into the Mackenzie Country to try to control the spread of rabbits. Black stilts are very vulnerable to these predators: they nest on the banks of streams and rivers, rather than islands; their nesting season begins in late winter, a time when rabbit numbers are low; and they currently nest as solitary pairs, so lose the protection of a colony (although they formed colonies in the past when numbers were higher). [2] Compared with pied stilts, they have more noticeable plumage, are less likely to perform distraction displays while incubating, and their chicks take longer to fledge. Intensive trapping and electric fences are used around black stilt breeding sites to control predators. Because most kakī nest on private land, DOC works with landowners to create a predator trapping network. [9]

Hybridisation

Hybridisation with far more numerous pied stilt is also a major threat to the black stilt gene pool. Hybridisation is a symptom of the continuing decline of the black stilt population; black stilts will choose the darkest-plumaged partner available, but mixed-species pairing can happen because potential black stilt mates are so rare. Black stilts mate for life, so those which pair with a pied stilt are lost to the breeding population. [2]

Habitat loss

Black stilts rely on wetlands and braided riverbeds for feeding, and these have been extensively drained or modified for agriculture, irrigation, and flood control. [6] Invasive weeds such as Russell lupin and crack willow are able to colonise braided riverbeds, reducing nesting habitat and providing cover for predators. [2]

Because black stilts nest on braided river beds, they are threatened by changes in river flows as a result of new and existing hydroelectric dams. [2] As part of the Upper Waitaki Power Development, braided riverbeds in the Upper Waitaki were receiving less water, which allowed weeds to encroach into black stilt breeding areas. These provided cover for predators, and from 1991 a new flow regime was introduced to reduce encroaching vegetation. [13] Artificial lowering of the level of Lake Benmore, which caused exposure of shallow riverbed in the deltas of the rivers that feed it, created temporary foraging areas for black stilts. [14]

Related Research Articles

<span class="mw-page-title-main">Stilt</span> Commons name for several species of bird

Stilt is a common name for several species of birds in the family Recurvirostridae, which also includes those known as avocets. They are found in brackish or saline wetlands in warm or hot climates.

<span class="mw-page-title-main">Recurvirostridae</span> Family of birds

The Recurvirostridae are a family of birds in the wader suborder Charadrii. It contains two distinct groups of birds, the avocets and the stilts.

<span class="mw-page-title-main">American avocet</span> Species of bird

The American avocet is a large wader in the avocet and stilt family, Recurvirostridae, found in North America. It spends much of its time foraging in shallow water or on mud flats, often sweeping its bill from side to side in water as it seeks crustacean and insect prey.

<span class="mw-page-title-main">Black-winged stilt</span> Species of bird

The black-winged stilt is a widely distributed, very long-legged wader in the avocet and stilt family Recurvirostridae. Its scientific name, Himantopus himantopus, is sometimes used to generalize a single, almost cosmopolitan species. Alternatively, it is restricted to the form that is widespread in Europe, Asia and Africa, which equals the nominate group of H. himantopussensu lato. Meanwhile, the black-necked and white-backed stilts both inhabit the Americas; the pied stilt ranges from Australasia and New Zealand. Today, most sources accept between one and four actual species.

<span class="mw-page-title-main">Mackenzie Basin</span> Area of land in the South Island of New Zealand

The Mackenzie Basin, popularly and traditionally known as the Mackenzie Country, is an elliptical intermontane basin located in the Mackenzie and Waitaki Districts, near the centre of the South Island of New Zealand. It is the largest such basin in New Zealand. Historically famous mainly for sheep farming, the sparsely populated area is now also a popular tourism destination.

<span class="mw-page-title-main">Banded stilt</span> Species of Australian bird in the family Recurvirostridae

The banded stilt is a nomadic wader of the stilt and avocet family, Recurvirostridae, native to Australia. It belongs to the monotypic genus Cladorhynchus. It gets its name from the red-brown breast band found on breeding adults, though this is mottled or entirely absent in non-breeding adults and juveniles. Its remaining plumage is pied and the eyes are dark brown. Nestling banded stilts have white down, unlike any other species of wader.

<span class="mw-page-title-main">White-fronted tern</span> Species of bird

The white-fronted tern, also known as tara, sea swallow, black-billed tern, kahawai bird, southern tern, or swallow tail, was first described by Johann Friedrich Gmelin in 1789. A medium-sized tern with an all-white body including underwing and forked tail, with grey hues on the over the upper side of the wing. In breeding adults a striking black cap covers the head from forehead to nape, leaving a small white strip above the black bill.

<span class="mw-page-title-main">Double-banded plover</span> Species of bird

The double-banded plover, known as the banded dotterel or pohowera in New Zealand, is a species of bird in the plover family. Two subspecies are recognised: the nominate Charadrius bicinctus bicinctus, which breeds throughout New Zealand, including the Chatham Islands, and Charadrius bicinctus exilis, which breeds in New Zealand's subantarctic Auckland Islands.

Hybridisation in shorebirds has been proven on only a small number of occasions; however, many individual shorebirds have been recorded by birdwatchers worldwide that do not fit the characters of known species. Many of these have been suspected of being hybrids. In several cases, shorebird hybrids have been described as new species before their hybrid origin was discovered. Compared to other groups of birds, only a few species of shorebirds are known or suspected to hybridise, but nonetheless, these hybrids occur quite frequently in some cases.

<span class="mw-page-title-main">Red-crowned parakeet</span> Species of bird

The red-crowned parakeet, also known as red-fronted parakeet and by its Māori name of kākāriki, is a small parrot from New Zealand. It is characterised by its bright green plumage and the red pattern on its head. This versatile bird can feed on a variety food items and can be found in many habitat types. It used to be classified as near threatened as invasive predators had pushed it out of its historical range but it is now at least concern. This species used to occupy the entire island, but is now confined to only a few areas on the mainland and some offshore islands.

<span class="mw-page-title-main">Wrybill</span> Species of bird

The wrybill or ngutuparore is a species of plover endemic to New Zealand. It is the only species of bird in the world with a beak that is bent sideways in one direction, always to the right. A 2015 study found it to be within the Charadrius clade, with other New Zealand plovers its closest relatives; the nearest being the New Zealand dotterel or New Zealand plover, and then the double-banded plover or banded dotterel.

<span class="mw-page-title-main">Black-fronted tern</span> Species of bird

The black-fronted tern, also known as sea martin, ploughboy, inland tern, riverbed tern or tarapiroe, is a small tern generally found in or near bodies of fresh water in New Zealand, where it forages for freshwater fish, arthropods and worms. It has a predominantly grey plumage. Restricted to breeding in the eastern regions of the South Island, it is declining and threatened by introduced mammals and birds. It is rated as endangered on the International Union for Conservation of Nature (IUCN)'s Red List of Threatened Species.

<span class="mw-page-title-main">Shore plover</span> Species of bird

The shore plover, also known as the shore dotterel, is a small plover endemic to New Zealand. Once found all around the New Zealand coast, it is now restricted to a few offshore islands. It is one of the world's rarest shorebirds: the population is roughly 200.

<span class="mw-page-title-main">Variable oystercatcher</span> Species of bird

The variable oystercatcher is a species of wader in the family Haematopodidae. It is endemic to New Zealand. The Māori name is tōrea-pango. They are also known as 'red bills'.

<span class="mw-page-title-main">Pied stilt</span> Species of bird

The pied stilt, also known as the white-headed stilt, is a shorebird in the family Recurvirostridae. It is widely distributed with a large total population size and apparently stable population trend, occurring in Malaysia, Japan, the Philippines, Brunei, Christmas Island, Indonesia, Palau, Papua New Guinea, Australia, and New Zealand. It is listed as Least Concern on the IUCN Red List. It is sometimes considered a subspecies of the black-winged stilt.

<span class="mw-page-title-main">Kermadec red-crowned parakeet</span> Subspecies of bird

The Kermadec red-crowned parakeet, also known as the Kermadec red-fronted parakeet or Kermadec parakeet, is a parrot endemic to New Zealand's Kermadec Islands in the south-west Pacific Ocean. It is a subspecies of the red-fronted parakeet, and sometimes considered a full species. It is also the first documented example of a parrot recolonising an island after the removal of invasive predators.

<span class="mw-page-title-main">Canterbury–Otago tussock grasslands</span> Terrestrial ecoregion in New Zealand

The Canterbury-Otago tussock grasslands is an ecoregion of the South Island, New Zealand, part of the wider tussock grasslands of New Zealand.

<span class="mw-page-title-main">Black-necked stilt</span> Species of bird

The black-necked stilt is a locally abundant shorebird of American wetlands and coastlines. It is found from the coastal areas of California through much of the interior western United States and along the Gulf of Mexico as far east as Florida, then south through Central America and the Caribbean to Brazil, Peru and the Galápagos Islands, with an isolated population, the Hawaiian stilt, in Hawaii. The northernmost populations, particularly those from inland, are migratory, wintering from the extreme south of the United States to southern Mexico, rarely as far south as Costa Rica; on the Baja California peninsula it is only found regularly in winter. Some authorities, including the IUCN, treat it as a synonym of Himantopus himantopus.

<span class="mw-page-title-main">Hawaiian stilt</span> Subspecies of bird

The Hawaiian stilt is an endangered Hawaiian subspecies of the black-necked stilt species. It is a long-legged, slender shorebird with a long, thin beak. Other common names include the Hawaiian black-necked stilt, the aeʻo, the kukuluaeʻo, or it may be referred to as the Hawaiian subspecies of the black-necked stilt.

References

  1. BirdLife International (2018). "Himantopus novaezelandiae". IUCN Red List of Threatened Species . 2018: e.T22693690A129560535. doi: 10.2305/IUCN.UK.2018-2.RLTS.T22693690A129560535.en . Retrieved 19 November 2021.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 Reed, C.E.M.; Murray, D.P.; Butler, D.J. (1993). Black Stilt Recovery Plan (Himantopus novaezealandiae) (PDF). Threatened Species Recovery Plan. Vol. 4. Wellington, New Zealand: Department of Conservation. ISBN   978-0-478-01459-4 . Retrieved 9 September 2008.
  3. 1 2 3 4 Heather, Barrie D.; Robertson, Hugh A. (2005). The Field Guide to the Birds of New Zealand. Auckland: Penguin. p. 94. ISBN   978-0-14-302040-0.
  4. 1 2 3 4 Worthy, Trevor H.; Holdaway, Richard N. (2002). The Lost World of the Moa. Bloomington: Indiana University Press. p. 412. ISBN   978-0-253-34034-4.
  5. 1 2 3 Birdlife International (2016). "Black Stilt Himantopus novaezelandiae". Birdlife International. Retrieved 23 April 2016.
  6. 1 2 White, Mike (March 2017). "Is New Zealand's black stilt on its last legs?". North & South.
  7. Toki, Nicola (21 April 2016). "Critter of the Week". Radio New Zealand. Retrieved 22 April 2016.
  8. "Black stilt/kakī". www.doc.govt.nz. Retrieved 4 September 2018.
  9. 1 2 3 "Stressed and endangered Kakī gain lockdown release after great breeding season". Stuff. 2 September 2021. Retrieved 5 September 2021.
  10. "Kakī release follows ramping up of predator control in Mackenzie Basin". RNZ. 10 August 2019. Retrieved 15 July 2020.
  11. "Kakī released after great breeding season". www.doc.govt.nz. Retrieved 4 September 2021.
  12. "Kakī settling into the wild for Conservation Week". www.doc.govt.nz. Retrieved 19 August 2023.
  13. Ministry for the Environment (May 1998). Flow Guidelines for Instream Values. ME 271 Volume B. Wellington, New Zealand: Ministry for the Environment . Retrieved 23 April 2016.
  14. Sanders, Mark (1999). "Effect of changes in water level on numbers of black stilts (Himantopus novaezelandiae) using deltas of Lake Benmore". New Zealand Journal of Zoology. 26 (2): 155–163. doi: 10.1080/03014223.1999.9518185 .