Chatham shag

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Chatham shag
20181001 ChathamsA9D3 444 DxO.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Suliformes
Family: Phalacrocoracidae
Genus: Leucocarbo
Species:
L. onslowi
Binomial name
Leucocarbo onslowi
(Forbes, 1893)
Synonyms

Phalacrocorax onslowi

The Chatham shag (Leucocarbo onslowi), also known as the Chatham Island shag, is a species of bird in the cormorant and shag family, Phalacrocoracidae. It is endemic to the Chatham Islands of New Zealand. For a long time the species was placed in the genus Phalacrocorax ; today it is mostly placed with the other blue-eyed shags of New Zealand and Antarctica in the genus Leucocarbo . Its closest relative is the Otago shag of South Island.

Contents

This is a large, pied shag with a long crest. It is highly coastal, rarely foraging far from shore, although sometimes feeds in the large and brackish Te Whanga Lagoon. It forages for fish and cephalopods and roosts on rocky shores. The species is colonial, breeding in small colonies around the Chatham Islands. Little is known about its breeding behaviour. The species is threatened by introduced predators, disturbance at its breeding colonies and habitat loss.

Taxonomy

New Zealand king shag

†Kohatu shag

Otago shag

Chatham shag

Foveaux shag

Phylogeny of the Blue-eyed shags of North, South and the Chatham Islands, showing the position of the Chatham shag, based on Rawlence et al, 2017

Henry Forbes described the Chatham shag as Phalacrocorax onslowi in 1893. The specific name commemorates William Onslow, 4th Earl of Onslow, who was the Governor of New Zealand between 1889 and 1892. [2] The question of which genus to place the species in has, like the general question of the taxonomy of the cormorants and shags on the whole, been a long-standing mystery. It was long retained in Phalacrocorax along with the rest of the family when the family was treated as monogeneric. It was also placed in the genus Euleucocarbo along with the other "blue-eyed shags" found in New Zealand. The species has sometimes been considered a subspecies of an enlarged New Zealand king shag species (Leucocarbo carunculatus). [3] Most recently a 2014 study of the mitochondrial and nuclear DNA of the family placed it within the New Zealand blue-eyed shags and the other Antarctic blue-eyed shags in the genus Leucocarbo . [4] This arrangement has also been adopted by the International Ornithologists' Union. [5] The same study found that its closest relative was the species formerly known as Stewart shag. [4] Since 2016, the Stewart shag is now treated as two species, the Otago and Foveaux shags. The same study that split these two species also found that the Chatham shag is closely related to the Otago shag and that this pair are in turn a sister clade to the Foveaux shag. [6] These three species are in turn related to the New Zealand king shag and an extinct Leucocarbo species, the Kohatu shag, from the far north of New Zealand. [7]

"Chatham Shag" has been designated as the official common name for the species by the IOC. [5] The species is also known as the "Chatham Island shag". [8]

Description

An adult Chatham shag is 63 cm (25 in) in length and weighs around 1,790–2,400 g (63–85 oz). [3] It is a large pied shag with a white throat, breast, belly and patches on the scapulars of the wings, and black or black-brown elsewhere. When breeding the head and hind-neck have a blue metallic sheen, the wings and mantle have a greenish sheen and the rest of the black areas have a purplish-blue sheen. The head has a prominent crest and there are white filoplumes on the neck. Adults have a red gular sac and orange-red caruncles on the face and the gape of the mouth. In spite of the common name of the genus the iris of the eye is brown, and the eye has a violet eye-ring. The bill is dark grey, with a bright red mouth, and the legs and feet are dull pink. Non-breeding birds look similar to breeding birds but are duller, have no crest or filoplumes, and duller bare parts. The caruncles are yellow, the eye-ring blue, the mouth orange and the bill is light-grey. [9]

Distribution and habitat

The Chatham shag is, as its name suggests, endemic to the Chatham Islands of New Zealand. Chatham Islands in New Zealand (zoom).svg
The Chatham shag is, as its name suggests, endemic to the Chatham Islands of New Zealand.

The species is endemic to the Chatham Islands, an archipelago around 700 km (430 mi) to the east of New Zealand. In the Chathams it is an inshore species, rarely going more than a few kilometres away from shore, and it is more commonly found in sheltered water such as bays and inlets. [3] It also forages in the large brackish Te Whanga Lagoon. [8] It breeds in colonies on coastal areas and around Te Whanga Lagoon, either on flat areas, slopes or wide cliff ledges. There are currently thirteen colonies of this species, found on the main Chatham Island as well as Pitt Island, Star Keys, Rabbit Island and North East Reef. These colonies are located close to the high-tide mark and can have as many as 300 nests in them. [10] It roosts on rocks close to shore or at sea, [3] although it may have different roosting sites for day and night. The species is non-migratory and has never been recorded away from the Chatham Islands, [9] although the species does feed and roost on islands in the Chathams away from their breeding colonies, for example Mangere. [11]

Behaviour

Diet and feeding

Like all cormorants, the Chatham shag is a pursuit-diver, propelling itself underwater with its feet and returning to the surface to consume small prey caught in its bill. [12] The specific diet of the Chatham shag is poorly known, [3] but is dominated by fish, including opalfish, flatfish and bullies, as well as cephalopods such as octopuses, squid and cuttlefish. It generally feeds alone, [8]  but will form small feeding flocks at times. [3]

Breeding

Little is known about the breeding biology. Males attract a mate with an advertising display in which it stands with its tail cocked up and throws its neck and head back towards its tail, up to 13 times, while making a gargling noise. Mated pairs recognise each other at the nest with gaping and head-lowering displays. During these the male makes a barking noise, but the female is almost silent, making only a soft puffing noise. [9]

Breeding is seasonal, and the timing of laying can vary from colony to colony. Most Chatham shags lay between October and December, but the colonies on Te Whanga Lagoon breed three months earlier than other colonies. [8] The nest is made of iceplant, grasses and other plants. Small nesting territories are defended from others of the species, and birds nesting in the centre of the colony have to run the gauntlet of biting to reach their nests as they pass other territories. [9] Two to four eggs are laid; [8] the eggs measure 59 to 63 mm (2.3–2.5 in) × 37 to 40 mm (1.5–1.6 in) and are matt pale blue with a chalky covering. [9] The incubation time is not known but is thought to be around 30 days. [8]

Conservation

The Chatham shag is threatened by a range of human activities and threats. The species is sensitive to disturbance at its breeding colonies, as nests are trampled by stampeding adults and nests are opportunistically raided by silver gulls after the eggs are unattended. At worst, entire colonies have been abandoned due to disturbance by people or stock. Colonies on the main islands are also vulnerable to introduced predators such as weka, feral cats and possums. It is considered critically endangered by the IUCN. [1]

Related Research Articles

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

Phalacrocoracidae is a family of approximately 40 species of aquatic birds commonly known as cormorants and shags. Several different classifications of the family have been proposed, but in 2021 the International Ornithologists' Union (IOU) adopted a consensus taxonomy of seven genera. The great cormorant and the common shag are the only two species of the family commonly encountered in Britain and Ireland and "cormorant" and "shag" appellations have been later assigned to different species in the family somewhat haphazardly.

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

The pelagic cormorant, also known as Baird's cormorant or violet-green cormorant, is a small member of the cormorant family Phalacrocoracidae. Analogous to other smallish cormorants, it is also called the pelagic shag occasionally. This seabird lives along the coasts of the northern Pacific; during winter it can also be found in the open ocean. Pelagic cormorants have relatively short wings due to their need for economical movement underwater, and consequently have the highest flight costs of any bird.

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

The European shag or common shag is a species of cormorant. It is the only member of the monotypic genus Gulosus. It breeds around the rocky coasts of western and southern Europe, southwest Asia and north Africa, mainly wintering in its breeding range except for the northernmost birds. In Britain this seabird is usually referred to as simply the shag. The scientific genus name derives from the Latin for glutton. The species name aristotelis commemorates the Greek philosopher Aristotle.

<span class="mw-page-title-main">Australian pied cormorant</span> Species of bird

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

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

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

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

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<span class="mw-page-title-main">New Zealand king shag</span> Species of bird

The New Zealand king shag, also known as the rough-faced shag, king shag or kawau tūī, is a rare bird endemic to New Zealand. Some taxonomic authorities, including the International Ornithologists' Union, place this species in the genus Leucocarbo. Others place it in the genus Phalacrocorax.

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

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

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

The red-legged cormorant, also known as the red-legged shag, red-footed cormorant, red-footed shag, Gaimard's cormorant and grey cormorant, is a species of cormorant resident to the coastline of South America. It is the only member of the genus Poikilocarbo. It is non-colonial unlike most seabirds. The red-legged cormorant has not been observed wing-spreading, which is unusual among cormorant species.

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

The Bounty shag, also known as the Bounty Island shag, is a species of cormorant of the family Phalacrocoracidae. They are found only on the tiny and remote Subantarctic Bounty Islands, 670 km (420 mi) southeast of New Zealand. Its natural habitats are open seas and rocky shores. In 2022, a full Unmanned aerial vehicle survey of the Bounty archipelago found a total of 573 breeding pairs and estimates the population to consist of approximately 1,733 birds. These recent estimates are consistent with the only other comparable study from 1978 and suggest that the species' population has remained stable over the past 45 years.

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

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<span class="mw-page-title-main">South Georgia shag</span> A species of bird

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<span class="mw-page-title-main">Heard Island shag</span> Species of bird

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<span class="mw-page-title-main">Macquarie shag</span> Species of cormorant

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<span class="mw-page-title-main">Suliformes</span> Order of birds

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

The Antarctic shag, sometimes referred to as the imperial cormorant, king cormorant, imperial shag, blue-eyed shag or Antarctic cormorant, is the only species of the cormorant family found in the Antarctic. It is sometimes considered conspecific with the Imperial shag.

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

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References

  1. 1 2 BirdLife International (2018). "Leucocarbo onslowi". IUCN Red List of Threatened Species . 2018: e.T22696861A131116322. doi: 10.2305/IUCN.UK.2018-2.RLTS.T22696861A131116322.en . Retrieved 17 November 2021.
  2. Jobling, J. A. (2019). del Hoyo, J.; Elliott, A.; Christie, D.; Sargatal, J. (eds.). "Key to Scientific Names in Ornithology". Handbook of the Birds of the World Alive. Barcelona: Lynx Edicions. Retrieved 25 March 2019.
  3. 1 2 3 4 5 6 Orta, J; Christie, D; Jutglar, F; Kirwan, G. M. (2019). del Hoyo, Josep; Elliott, Andrew; Sargatal, Jordi; Christie, David A; de Juana, Eduardo (eds.). "Chatham Shag (Leucocarbo onslowi)" . Handbook of the Birds of the World Alive. Barcelona: Lynx Edicions. doi:10.2173/bow.chisha1.01.1. S2CID   242270837 . Retrieved 25 March 2019.
  4. 1 2 Kennedy, Martyn; Spencer, Hamish G. (October 2014). "Classification of the cormorants of the world". Molecular Phylogenetics and Evolution. 79: 249–257. doi:10.1016/j.ympev.2014.06.020. PMID   24994028.[ dead link ]
  5. 1 2 Gill, Frank; Donsker, David, eds. (2019). "Hamerkop, Shoebill, pelicans, boobies, cormorants". World Bird List Version 9.1. International Ornithologists' Union. Archived from the original on 23 April 2020. Retrieved 30 March 2019.
  6. Rawlence, Nicolas J.; Scofield, R. Paul; Spencer, Hamish G.; Lalas, Chris; Easton, Luke J.; Tennyson, Alan J.D.; Adams, Mark; Pasquet, Eric; Fraser, Cody; Waters, Jonathan M.; Kennedy, Martyn (2016). "Genetic and morphological evidence for two species of Leucocarbo shag (Aves, Pelecaniformes, Phalacrocoracidae) from southern South Island of New Zealand". Zoological Journal of the Linnean Society. 177 (3): 676–694. doi: 10.1111/zoj.12376 .
  7. Rawlence, Nicolas J.; Till, Charlotte E.; Easton, Luke J.; Spencer, Hamish G.; Schuckard, Rob; Melville, David S.; Scofield, R. Paul; Tennyson, Alan J.D.; Rayner, Matt J.; Waters, Jonathan M.; Kennedy, Martyn (2017). "Speciation, range contraction and extinction in the endemic New Zealand King Shag complex". Molecular Phylogenetics and Evolution. 115: 197–209. doi:10.1016/j.ympev.2017.07.011. PMID   28803756.
  8. 1 2 3 4 5 6 Bell, M (2013). Miskelly, Colin (ed.). "Chatham Island shag". New Zealand Birds Online. Retrieved 25 March 2019.
  9. 1 2 3 4 5 Marchant, S.; Higgins, P. J., eds. (1990). Handbook of Australian, New Zealand and Antarctic Birds. Volume 1: Ratites to ducks; Part B, Australian pelican to ducks. Melbourne: Oxford University Press. pp. 881–884. ISBN   9780195530681.
  10. Bell, M; Bell, D; Boyle, D; Tuanui-Chisholm, H (2017). "Chatham Island Shag census 2014–2016" (PDF). Technical Report to the Department of Conservation.
  11. Nilsson, R; Kennedy, E; West, J (1994). "The birdlife of South East Island (Rangatira), Chatham Islands, New Zealand" (PDF). Notornis. 41: 109–125.
  12. Orta, J (2019). del Hoyo, Josep; Elliott, Andrew; Sargatal, Jordi; Christie, David A; de Juana, Eduardo (eds.). "Cormorants (Phalacrocoracidae)" . Handbook of the Birds of the World Alive. Barcelona: Lynx Edicions. doi:10.2173/bow.phalac1.01. S2CID   216251345 . Retrieved 26 March 2019.