The Foveaux shag (''Leucocarbo stewarti''), together with the

Otago shag The Otago shag, (''Leucocarbo chalconotus''), together with the Foveaux shag formerly known as the Stewart Island shag and in its dark phase as the bronze shag, is a species of shag now found only in coastal Otago, New Zealand. Description ...

formerly known as the

Stewart Island shag Stewart Island shag or Stewart shag was the former name of a species of cormorant that was split into two species as a result of genetic studies. The two resulting species are: * Otago shag, ''Leucocarbo chalconotus'', which is endemic to coastal ...

and in its dark phase as the bronze shag, is a species of

shag Shag, or Shagged, or Shagger, or Shagging, or Shags may refer to: Animals * Shag or cormorant, a bird family ** European shag, a specific species of the shag or cormorant family ** Great cormorant another species of the family People Pseudonym ...

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

Stewart Island/Rakiura Stewart Island ( mi, Rakiura, ' glowing skies', officially Stewart Island / Rakiura) is New Zealand's third-largest island, located south of the South Island, across the Foveaux Strait. It is a roughly triangular island with a total land ar ...

and

Foveaux Strait The Foveaux Strait, (, or , ) separates Stewart Island, New Zealand's third largest island, from the South Island. The strait is about 130 km long (from Ruapuke Island to Little Solander Island), and it widens (from 14 km at Ruapuk ...

, from which it takes its name. PhalacrocoraxStewartiKeulemans

Taxonomy

Until 2016 Foveaux shags were classified with Otago shags (''L. chalconotus'') in a single species, called the Stewart Island shag. Mitochondrial DNA suggests Otago shags are actually more closely related to

Chatham shag 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 plac ...

s (''Leucocarbo onslowi''), and

osteological Osteology () is the scientific study of bones, practised by osteologists. A subdiscipline of anatomy, anthropology, and paleontology, osteology is the detailed study of the structure of bones, skeletal elements, teeth, microbone morphology, funct ...

, morphological,

morphometric Morphometrics (from Greek μορϕή ''morphe'', "shape, form", and -μετρία ''metria'', "measurement") or morphometry refers to the quantitative analysis of ''form'', a concept that encompasses size and shape. Morphometric analyses are co ...

, behavioural, and genetic differences supported recognising Foveaux shags as a separate species, ''L. stewarti''. Foveaux and Otago shags probably diverged when populations were split up by lower sea levels in the

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

, and the

Chatham Islands The Chatham Islands ( ) (Moriori: ''Rēkohu'', 'Misty Sun'; mi, Wharekauri) are an archipelago in the Pacific Ocean about east of New Zealand's South Island. They are administered as part of New Zealand. The archipelago consists of about te ...

were colonised by shags from

Otago Otago (, ; mi, Ōtākou ) is a region of New Zealand located in the southern half of the South Island administered by the Otago Regional Council. It has an area of approximately , making it the country's second largest local government reg ...

. Other taxonomists have kept the Otago shag and the Foveaux shag conspecific. A recent taxonomic revision argues that ''Leucocarbo'' is a distinct genus, which would contain amongst other species the Otago, Foveaux, and Chatham shags.

Description

The species is dimorphic, with two plumages. Roughly half the individuals are pied, with dark and white feathers, and the rest are dark all over. Both morphs breed together. These large, chunky birds are 68 cm (27 in) long and weigh 1.8–2.9 kg (4–6.4 lbs), slightly smaller than

s. Foveaux shags can be distinguished from Otago shags by their facial ornamentation in the breeding season: Foveaux shags have dark orange papillae on their face, whereas Otago shags have both papillae and small bright orange facial caruncles above the base of the bill.

Distribution and conservation

Foveaux shags are restricted to Stewart Island and Foveaux Strait, both at present, historically, and prehistorically (based on museum specimens, archaeological remains, and

subfossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...

bones); rarely, beach-wrecked birds have been found in Otago. They breed colonially from September onwards, making raised cup nests out of organic material and

guano Guano (Spanish from qu, wanu) is the accumulated excrement of seabirds or bats. As a manure, guano is a highly effective fertilizer due to the high content of nitrogen, phosphate, and potassium, all key nutrients essential for plant growth. G ...

on islands and sea cliffs. Colonies are large enough to be strikingly visible, and are used year after year. They feed in coastal waters less than 30 m deep and are rarely if ever seen inland or far out to sea. There are less than 2500 Foveaux shags remaining. The population seems stable and retains much of its genetic diversity in comparison to the Otago shag, which is continuing to decline. Foveaux shags have fared better than Otago shags because they nest on inaccessible islands just offshore. Nevertheless, their small population size make both species vulnerable to extinction, and conservation efforts will need to be tailored to each species' demographic history, genetic variation, and restricted geographic distribution.

References

External links

Foveaux shag discussed on RadioNZ ''Critter of the Week''
4 March 2016
{{Taxonbar, from=Q24551139

Foveaux shag The Foveaux shag (''Leucocarbo stewarti''), together with the Otago shag formerly known as the Stewart Island shag and in its dark phase as the bronze shag, is a species of shag endemic to Stewart Island/Rakiura and Foveaux Strait, from which i ...

Birds of the South Island

Endemic birds of New Zealand