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The great cormorant (''Phalacrocorax carbo''), known as the black shag in New Zealand and 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 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 IOC adopted a consensus taxonomy of seven gen ...
family of
seabird Seabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same envir ...
s. The genus name is Latinised Ancient Greek, from φαλακρός (''phalakros'', "bald") and κόραξ (''korax'', "raven"), and ''carbo'' is Latin for "
charcoal Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, cal ...
". It breeds in much of the
Old World The "Old World" is a term for Afro-Eurasia that originated in Europe , after Europeans became aware of the existence of the Americas. It is used to contrast the continents of Africa, Europe, and Asia, which were previously thought of by th ...
, Australia, and the Atlantic coast of North America.


Taxonomy and etymology

The long white-breasted cormorant ''P. c. lucidus'' found in sub-Saharan Africa, has a white neck and breast. It is often treated as a full species, ''Phalacrocorax lucidus'' (e.g. , ). In addition to the Australasian and African forms, ''Phalacrocorax carbo novaehollandiae'' and ''P. c. lucidus'' mentioned above, other geographically distinct subspecies are recognised, including ''P. c. sinensis'' (western Europe to east
Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...
), ''P. c. maroccanus'' (north-western Africa), and ''P. c. hanedae'' ( Japan). Some authors treat all these as allospecies of a ''P. carbo'' superspecies group. In New Zealand, the subspecies ''P. c. novaehollandiae'' is known as the black shag or by its
Māori Māori or Maori can refer to: Relating to the Māori people * Māori people of New Zealand, or members of that group * Māori language, the language of the Māori people of New Zealand * Māori culture * Cook Islanders, the Māori people of the Co ...
name; "kawau". The syntype is in the collection of the Museum of New Zealand Te Papa Tongarewa.


Description

The great cormorant is a large black bird, but there is a wide variation in size in the species' wide range. Weight is reported to vary from to . Males are typically larger and heavier than females, with the nominate race (''P. c. carbo'') averaging about 10% larger in linear measurements than the smallest race in Europe (''P. c. sinensis''). The lightest average weights cited are in Germany (''P. c. sinensis''), where 36 males averaged and 17 females averaged . The highest come from Prince Edward Island in Canada (''P. c. carbo''), where 11 males averaged and 11 females averaged . Length can vary from and wingspan from . They are tied as the second largest extant species of cormorant after the
flightless cormorant The flightless cormorant (''Nannopterum harrisi''), also known as the Galapagos cormorant, is a cormorant endemic to the Galapagos Islands, and an example of the highly unusual fauna there. It is unique in that it is the only known cormorant th ...
, with the
Japanese cormorant The Japanese cormorant (''Phalacrocorax capillatus''), also known as Temminck's cormorant, is a cormorant native to the east Palearctic. It lives from Taiwan, north through Korea and Japan, to the Russian Far East. The Japanese cormorant has a b ...
averaging at a similar size. In bulk if not in linear dimensions, the
Blue-eyed shag ''Leucocarbo'' is a genus of birds in the family Phalacrocoracidae with the members commonly known as blue-eyed shags. This is a group of closely related cormorant taxa. Many have a blue, purple or red ring around the eye (not a blue iris); other ...
species complex of the Southern Oceans are scarcely smaller at average. It has a longish tail and yellow throat-patch. Adults have white patches on the thighs and on the throat in the breeding season. In European waters it can be distinguished from the
common shag The European shag or common shag (''Gulosus aristotelis'') 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, mai ...
by its larger size, heavier build, thicker bill, lack of a crest and
plumage Plumage ( "feather") is a layer of feathers that covers a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage differ between species and subspecies and may vary with age classes. Within species, ...
without any green tinge. In eastern North America, it is similarly larger and bulkier than double-crested cormorant, and the latter species has more yellow on the throat and bill and lack the white thigh patches frequently seen on great cormorants. Great cormorants are mostly silent, but they make various guttural noises at their breeding colonies.


Variations

A very rare variation of the great cormorant is caused by
albinism Albinism is the congenital absence of melanin in an animal or plant resulting in white hair, feathers, scales and skin and pink or blue eyes. Individuals with the condition are referred to as albino. Varied use and interpretation of the term ...
. The ''Phalacrocorax carbo'' albino suffers from poor eyesight and/or hearing, thus it rarely manages to survive in the wild.


Distribution

This is a very common and widespread bird species. It feeds on the sea, in
estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environmen ...
, and on freshwater lakes and rivers. Northern birds migrate south and winter along any coast that is well-supplied with fish. In Serbia, the cormorant lives in Vojvodina. However, after 1945 many artificial lakes were formed in Serbia; some of them became potential habitats for cormorants. Currently, on the Lake Ćelije, formed in 1980, there is a resident colony of cormorants, who nest there and are present throughout the year, except January–February 1985 and February 2012 when the lake surface was completely frozen. The type subspecies, ''P. c. carbo'', is found mainly in Atlantic waters and nearby inland areas: on western European coasts and east across the Palearctic to Siberia and to North Africa, the
Faroe Islands The Faroe Islands ( ), or simply the Faroes ( fo, Føroyar ; da, Færøerne ), are a North Atlantic archipelago, island group and an autonomous territory of the Danish Realm, Kingdom of Denmark. They are located north-northwest of Scotlan ...
, Iceland and Greenland; and on the eastern seaboard of North America. The subspecies ''P. c. novaehollandiae'' is found in Australian waters.


Behaviour


Breeding

The great cormorant often 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. This cormorant lays a
clutch A clutch is a mechanical device that engages and disengages power transmission, especially from a drive shaft to a driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). ...
of three to five eggs that measure 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.


Feeding

The great cormorant feeds on fish caught through diving. This bird feeds primarily on wrasses, but it also takes sand smelt, flathead and
common sole The common sole, Dover sole, or black sole (''Solea solea'') is a species of flatfish in the family Soleidae. It is one of the largest fish in the '' Solea'' genus. It lives on the sandy or muddy seabed of the northern Atlantic and the Mediterr ...
s. The average weight of fish taken by great cormorants increased with decreasing air and water temperature, being 30 g during summer, 109 g during a warm winter and 157 g during the cold winter (all values for non-breeding birds). 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. Thus, the winter elevation of foraging efficiency described for cormorants by various researchers is due to capturing larger fish not due to capturing more fish. In some freshwater systems, the losses of fish due to overwintering great cormorants were estimated to be up to 80 kg per ha each year (e.g. Vltava River, Czech Republic). This cormorant forages by diving and capturing its prey in its beak. The duration of its dives is around 28 seconds, with the bird diving to depths of about . About 60% of dives are to the
benthic zone The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...
and about 10% are to the pelagic zone, with the rest of the dives being to zones in between the two. Studies suggest that their hearing has evolved for underwater usage, possibly aiding their detection of fish. These adaptations also have a cost on their hearing ability in air which is of lowered sensitivity.


Relationships with humans

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). Increasing populations have once again brought the cormorant into conflict with fisheries. 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 In biology, culling is the process of segregating organisms from a group according to desired or undesired characteristics. In animal breeding, it is the process of removing or segregating animals from a breeding stock based on a specific tr ...
specified numbers of cormorants in order to help reduce predation; it is, however, still illegal to kill a bird without such a licence.
Cormorant fishing Cormorant fishing is a traditional fishing technique in which fishermen use trained cormorants to catch fish in rivers. Historically, cormorant fishing has taken place in Japan and China, as well as Greece, North Macedonia, and briefly, England ...
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. In Norway, the cormorant is a traditional game bird. Each year approximately 10,000 cormorants are shot to be eaten. In North Norway, cormorants are traditionally seen as semi-sacred. It is regarded as good luck to have cormorants gather near your village or settlement. An old legend states that for 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.


Gallery

File:Phalacrocorax carbo MWNH 0534.JPG, Egg, Collection
Museum Wiesbaden The Museum Wiesbaden is a two-branch museum of art and natural history in the Hessian capital of Wiesbaden, Germany. It is one of the three Hessian State museums, in addition to the museums in Kassel and Darmstadt. History The foundation o ...
File:Phalacrocorax Carbo Albino 2.jpg, Albino in
Lake Kerkini Lake Kerkini ( gr, Λίμνη Κερκίνη - Limni Kerkini) is an artificial reservoir in Central Macedonia, Greece that was created in 1932, and then redeveloped in 1980, on the site of what was previously an extremely extensive marshland. L ...
, Greece File:Great cormorant (Phalacrocorax carbo) immature.jpg, immature, Kazinga Channel, Uganda File:Storskarv - Kranium - Phalacrocorax carbo.jpg, Cranium File:Great cormorant (Phalacrocorax carbo).JPG, On Farmoor Reservoir, Oxfordshire File:Great cormorant (Phalacrocorax carbo) in flight.jpg, Above Farmoor Reservoir, Oxfordshire File:Lithuania Juodkrante Great Cormorant colony 1.jpg, Colony in Juodkrantė, Lithuania, and damage to the trees in which they are nesting File:Merimetsokolonia Enäjärven saaressa 2.jpg, Colony in Finland File:Aalscholver Phalacrocorax carbo Jos Zwarts 2.tif, Drawing by Jos Zwarts File:Kormorane in lake Vistonis.jpg, In lake Vistonis, Greece File:GreatCormorantLanding.jpg, Adult landing on Dambovita River,Bucharest


Videos

File:Aalscholver op havenpaal-4676903.webm, Resting on a post in a port in Den Oever, the Netherlands File:Aalscholver op paal-4676900.webm, Stretching wings while sitting on a pole File:Chasse du Grand Cormoran.webm, Great cormorant hunting in Odessa


References


Further reading

* * ;Separation of ''carbo'' and ''sinensis'' * * * Murray, T and Cabot, D. (2015). The Breeding Status of Great Cormorant (''Phalacrocorax carbo carbo'') in Co. Wexford. ''Ir. Nat. J.'' 34: 89–94.


External links

*
Great cormorant Species text in The Atlas of Southern African Birds
* * * * * * {{Authority control great cormorant Cosmopolitan birds great cormorant Articles containing video clips Birds of Nepal great cormorant Holarctic birds