Great cormorant

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File:Great cormorants (Phalacrocorax carbo) Lapmezciems.jpg

Group of great cormorants in Latvia

The great cormorant (Phalacrocorax carbo), also known as just cormorant in Britain, as black shag or kawau in New Zealand, formerly also known as the great black cormorant across the Northern Hemisphere, the black cormorant in Australia, and the large cormorant in India, is a widespread member of the cormorant family of seabirds.<ref name=Ali1993/> It breeds in much of the Old World, Australasia, and the Atlantic coast of North America.

TaxonomyEdit

The great cormorant was formally described in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his Systema Naturae under the binomial name Pelecanus carbo.<ref>Template:Cite book</ref> Linnaeus specified the type location as "Europe", but this was restricted to the "rock-nesting form of the north Atlantic Ocean" by the German ornithologist Ernst Hartert in 1920.<ref>Template:Cite book</ref><ref>Template:Cite book</ref> The great cormorant is now one of 12 species placed in the genus Phalacrocorax that was introduced in 1760 by the French zoologist Mathurin Jacques Brisson.<ref name=ioc>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The genus name is Latinised Ancient Greek, from φαλακρός (phalakros, "bald") and κόραξ (korax, "raven"); the specific epithet carbo is Latin for "charcoal".<ref>Template:Cite book</ref>

Six subspecies are accepted. These are listed below with their breeding ranges.<ref name=ioc/> An additional species, the Japanese cormorant Phalacrocorax capillatus, is very closely related, with genetic evidence suggesting it may be embedded within P. carbo;<ref name=kennedy2014>Template:Cite journal</ref> it is shown in the list below for completeness.

Image	Scientific name	Common name	Distribution	Notes
File:2021-05-05 Phalacrocorax carbo carbo, Killingworth Lake, Northumberland 2-1.jpg Northumberland, UK	P. c. carbo (Linnaeus, 1758)	Atlantic cormorant	North Atlantic coasts from NW France, Britain, Ireland, western Norway, west Greenland, and east Canada to Maine (northeast USA), wintering south to north Florida; formerly also the Baltic Sea	Described by Linnaeus from Sweden in 1758, but extinct there soon after; subsequent recolonisation of the area has been by P. c. sinensis<ref>Template:Cite journal</ref>
File:Great Cormorant (Phalacrocorax carbo) (53433200109).jpg Gojal, Gilgit-Baltistan, Pakistan	P. c. sinensis (Staunton, 1796) syn. P. c. subcormoranus (C. L. Brehm, 1824)	Continental cormorant large cormorant (India)	Transcontinental across Eurasia from inland western Europe to India and Sri Lanka, to northeast Russia, northeast China and the Korean Peninsula, south to Turkey, central Asia and north Mongolia; also disjunct in central south Cambodia and south Vietnam, northeast Borneo	Spreading north and west; now overlaps and interbreeds with P. c. carbo in at least southeast England, northern France, the Netherlands, and Scandinavia<ref name="Newson">Template:Cite journal</ref>
File:Great cormorant at Tennōji Park in Osaka, December 2023 - 6091.jpg Osaka, Japan	P. c. hanedae Kuroda & Nm, 1925	Japanese great cormorant	coastal and inland Japan, Hokkaido to Kyushu (north to south Japan)	Ecologically separated from P. capillatus, less strictly marine, often inland
File:Moroccan Cormorant Phalacrocorax carbo moroccanus (8470661800).jpg Souss-Massa National Park, Morocco	P. c. maroccanus Hartert, EJO, 1906	Moroccan cormorant	coastal northwest Africa: Morocco to Mauretania	white neck and upper breast
File:Lake Naivasha 2017 06.jpg Lake Naivasha, Kenya	P. c. lucidus Lichtenstein, MHC, 1823	White-breasted cormorant	sub-Saharan Africa	white neck and breast
File:Phalacrocorax carbo Vic.jpg Victoria, Australia	P. c. novaehollandiae Stephens, 1826	black cormorant (Australia) black shag (New Zealand), kawau (New Zealand, Māori name)<ref name=FGBNZ/>	inland and coastal Australasia: Australia, North Island, South Island, Stewart Island and Chatham Islands (east of South Island; New Zealand), Rennell Island (south Solomon Islands) and Grande Terre (New Caledonia)	Syntype in the collection of the Museum of New Zealand Te Papa Tongarewa.<ref name=tepapa/>
File:Phalacrocorax capillatus on Tetrapod.jpg Aichi prefecture, Japan	P. capillatus (Temminck & Schlegel, 1850)	Japanese cormorant	coastal Japan Hokkaido to Kyushu, Sakhalin, southeast Russia, Korea	Ecologically separated from P. c. hanedae, more strictly marine, rarely inland

DescriptionEdit

The great cormorant is a large bird, but there is a wide variation in size in the species' wide range. Weight is reported to vary from Template:Convert<ref name=Ribak2005/> to Template:Convert.<ref name=CanadianEncyclopedia/> Males are typically larger and heavier than females, with the nominate race P. c. carbo averaging about 10% larger in linear measurements than the smaller subspecies P. c. sinensis.<ref name=Koffijberg1995/> The lightest average weights cited are in Germany (P. c. sinensis), where 36 males averaged Template:Convert and 17 females averaged Template:Convert.<ref name=CRC/> The highest come from Prince Edward Island in Canada (P. c. carbo), where 11 males averaged Template:Convert and 11 females averaged Template:Convert.<ref name=Hogan1979/><ref name=Hatch/> Length can vary from Template:Convert and wingspan from Template:Convert.<ref name=Hatch/><ref name=Stevenson/> They are tied as the second largest extant species of cormorant after the flightless cormorant, with the Japanese cormorant averaging at a similar size. In bulk if not in linear dimensions, the blue-eyed shag species complex of the Southern Oceans is only marginally smaller on average.<ref name=CRC/>

The plumage is largely black, but with bronze to greenish iridescence on the wings and tail, and purple iridescence on the body. The eyes are a striking deep sea-green in adults, duller dark grey in juveniles. The tail is fairly long, with 14 feathers. The bill is stout, and strongly hooked at the tip, dark grey at the tip, grading to paler at the base; it also has a yellow, or sometimes red, patch of bare gular skin on the throat at the base of the bill. The legs are short but stout, and dark grey; the feet large, and fully webbed between all four toes (totipalmate). In the breeding season, adults have white filoplume patches on the thighs and on the head and upper neck. The two African subspecies P. c. maroccanus and P. c. lucidus also have more extensive white plumage on the foreneck and breast. In winter, the plumage is more uniformly black, slightly duller and less glossy, and the white filoplumes are shed. Juveniles and immatures have pale to whitish underparts, becoming browner in their second year and reaching adult plumage when 3–4 years old.<ref name="Cramp">Template:Cite book</ref><ref name="BirdGuides">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Great cormorants are mostly silent, but they make various guttural noises at their breeding colonies.<ref name="Cramp"/>

In European waters the great cormorant can be distinguished from the European shag by its larger size, heavier build, thicker bill, lack of a crest and body plumage with a purple, not green, tinge. In eastern North America, it is similarly larger and bulkier than the double-crested cormorant; the latter species also has more yellow on the throat and bill and lacks the white thigh patches seen on breeding plumage adult great cormorants. Both European shag and double-crested cormorant also differ in having 12, not 14, tail feathers.<ref name="Cramp"/><ref name="BirdGuides"/> Identification between the great cormorant subspecies is difficult, and complicated by hybridisation between the subspecies; the most useful character is the shape of the gular skin patch, which forms an acute angle in nominate P. c. carbo, and an obtuse angle in P. c. sinensis;<ref>Template:Cite journal</ref><ref name="BirdGuides"/> similar variation is used to distinguish P. c. hanedae and P. capillatus in eastern Asia.<ref>Template:Cite</ref> Differentiation between the two white-breasted African subspecies remains complex and uncertain.<ref name="Bergier">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Great cormorant (Phalacrocorax carbo),.jpg

Great cormorant at Ponnani, Malappuram, Kerala, India
Phalacrocorax Carbo Albino 2.jpg

Albino in Lake Kerkini, Greece
Storskarv - Kranium - Phalacrocorax carbo.jpg

Cranium
2024-11-02 Germany, Berlin, Great cormorant DSC 9409 DxO 2.jpg

Great cormorant about to take off in Berlin, Germany
Great cormorant (Phalacrocorax carbo) in flight.jpg

In flight, Farmoor Reservoir, Oxfordshire

VariationEdit

The white filoplumes on the head in the breeding season vary with both the age of the bird, and the subspecies; older birds have more white filoplumes than younger birds, while nominate P. c. carbo tends to have fewer than P. c. sinensis, but there is much overlap. The extent of variation between individuals means it is not a very useful character for subspecies identification.<ref name="Sommer">Template:Cite journal</ref>

A very rare variation of the great cormorant is caused by albinism. Albinos suffer from poor eyesight and/or hearing, thus it rarely manages to survive in the wild.Template:Citation needed

DistributionEdit

This is a very common and widespread bird species. It feeds at sea in inshore waters, in estuaries, and on freshwater lakes and rivers. Northern birds migrate south to escape waters that freeze in winter, moving to any coast or freshwater that is unfrozen and well-supplied with fish; in warmer areas, birds disperse locally.<ref name="Cramp"/> They only rarely cross larger bodies of water such as the North Sea.<ref name="Cramp"/>

The type subspecies, P. c. carbo, is found mainly in Atlantic waters and nearby inland areas, on northwestern European coasts, the Faroe Islands, Iceland and Greenland, and on the northeastern seaboard of North America. The widespread continental subspecies P. c. sinensis occurs on most of mainland Europe and east across the Palearctic to Siberia and southeastern Asia.<ref name="Cramp"/> The subspecies P. c. novaehollandiae is found in Australian and New Zealand waters.<ref name=FGBNZ/>

BehaviourEdit

BreedingEdit

The great cormorant nests in colonies near wetlands, rivers, and sheltered inshore waters. Pairs will use the same nest site to breed year after year. It builds its nest, which is made from sticks, in trees, on the ledges of cliffs, and on the ground on rocky islands that are free of predators.<ref name="Hauber2014">Template:Cite book</ref> They lay a clutch of three to five eggs that measure Template:Convert on average. The eggs are a pale blue or green, and sometimes have a white chalky layer covering them. These eggs are incubated for a period of about 28 to 31 days.<ref name="Hauber2014"/>

Phalacrocorax carbo MWNH 0534.JPG

Egg, Collection Museum Wiesbaden
Lithuania Juodkrante Great Cormorant colony 1.jpg

Colony in Juodkrantė, Lithuania, and damage to the trees in which they are nesting
Merimetsokolonia Enäjärven saaressa 2.jpg

Colony in Finland

Food and feedingEdit

The great cormorant feeds on fish caught through diving.<ref name="Cramp"/><ref name="Hauber2014" /> Birds at the Chausey Islands feed primarily on wrasses, but also takes sand smelt, flathead and common soles.<ref name="GrémilletArgentin2008" /> The average weight of fish taken by great cormorants increases with decreasing air and water temperature. Cormorants consume all fish of appropriate size that they are able to catch in summer and noticeably select for larger, mostly torpedo-shaped fish in winter. In winter, the foraging efficiency described for cormorants by various researchers is increased by capturing larger fish, not due to capturing more fish.<ref>Template:Cite journal</ref> In some freshwater systems, the take of fish by overwintering great cormorants was estimated to be up to 80 kg per ha per year (e.g. Vltava River, Czech Republic).<ref>Template:Cite journal</ref>

It forages by foot-propelled diving and capturing its prey in its beak. The duration of its dives varies from 1–3 minutes, with the bird diving to depths of up to a maximum of Template:Convert.<ref name="Cramp"/> About 60% of dives are to the benthic zone and about 10% are to the pelagic zone, with the rest of the dives being to zones in between the two.<ref name="GrémilletArgentin2008">Template:Cite journal</ref> Studies suggest that their hearing has evolved for underwater usage, possibly aiding their detection of fish.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> These adaptations also have a cost on their hearing ability in air which is of lowered sensitivity.<ref>Template:Cite journal</ref>

GreatCormorantDiving.jpg

Diving in Dambovita River, Bucharest
Anguilla anguilla, Cheshire, England, GB imported from iNaturalist photo 74482397.jpg

With a European eel, in England
Greater cormorant in Action 01.jpg

Swallowing a bronze featherback at Keoladeo Ghana National Park, Bharatpur
GreatCormorant.jpg

Eating a carp, in Taudaha Lake, Nepal

Relationships with humansEdit

Many fishermen see in the great cormorant a competitor for fish. Because of this, it was hunted nearly to extinction in the past. Due to conservation efforts, its numbers increased. At the moment, there are about 1.2 million birds in Europe (based on winter counts; late summer counts would show higher numbers).<ref name="WICRG" /> Increasing populations have once again brought the cormorant into conflict with fisheries.<ref name="FAO" /><ref name="europarl" /> For example, in Britain, where inland breeding was once uncommon, there are now increasing numbers of birds breeding inland, and many inland fish farms and fisheries now claim to be suffering high losses due to these birds. In the UK each year, some licences are issued to cull specified numbers of cormorants in order to help reduce predation; it is, however, still illegal to kill a bird without such a licence.<ref>Template:Cite news</ref>

File:Wuzhen Xizha 2009-01-2.jpg

Cormorant fishing in Wuzhen Xizha, Zhejiang, China

Cormorant fishing is practised in China, Japan, and elsewhere around the globe. In this practice, fishermen tie a line around the throats of cormorants, tight enough to prevent swallowing the larger fish they catch, and deploy them from small boats. The cormorants catch fish without being able to fully swallow them, and the fishermen are able to retrieve the fish simply by forcing open the cormorants' mouths, apparently engaging the regurgitation reflex.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> To encourage its cooperation, the fisherman would reward the cormorant by letting it keep every eighth fish. The cormorants would eventually recognise this pattern and refuse to perform the eighth dive unless the fishing line was untied, and if the reward fish was not provided it would refuse to dive altogether.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

In Norway, the cormorant is a traditional game bird. Each year approximately 10,000 cormorants are shot to be eaten.<ref name="intercafeproject" /> In North Norway, cormorants are traditionally seen as semi-sacred.Template:Citation needed It is regarded as good luck to have cormorants gather near your village or settlement. An old legend states that people who die far out at sea, whose bodies are never recovered, spend eternity on the island Utrøst – which can only occasionally be found by mortals. The inhabitants of Utrøst can only visit their homes in the shape of cormorants.Template:Citation needed

VideosEdit

Aalscholver op havenpaal-4676903.webm

Resting on a post in a port in Den Oever, the Netherlands
Aalscholver op paal-4676900.webm

Stretching wings while sitting on a pole
Chasse du Grand Cormoran.webm

Great cormorant hunting in Odessa
Phalacrocorax carbo Great Cormorant 20171009 MVI 4344.ogg

Great cormorant, drying wings at Lake Juniko (十二湖) in Aomori, Japan
Aalscholver in broedkleed op ijs-4676907.webm

Adult great cormorant in breeding plumage, Texel, Netherlands (2010)