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Lifespan, longevity, and ageing

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Maximum longevity: 23.5 years (wild)
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Benefits

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There are no known adverse effects of great cormorants on humans. They are sometimes suspected of competing or interfering with human commercial and subsistence fishing, but their heavy reliance on small fishes means that it is unlikely they compete directly.

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Dewey, T. 2009. "Phalacrocorax carbo" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phalacrocorax_carbo.html
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Associations

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Most predation is at nesting colonies and the location and physical aspects of the nesting colony determine susceptibility to predation. Predators on eggs and hatchlings include gulls and crows, although they are generally only successful when colonies have been disturbed and adults are flushed from nests. Fledglings have been taken by bald eagles (Haliaeetus leucocephalus), white-tailed eagles (Haliaeetus albicilla), and red foxes (Vulpes vulpes). The presence of humans or large predators will cause adults to leave nests, leaving them vulnerable to predation.

Known Predators:

  • bald eagles (Haliaeetus leucocephalus)
  • white-tailed eagles (Haliaeetus albicilla)
  • red foxes (Vulpes vulpes)
  • gulls (Larus)
  • crows (Corvus)
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Dewey, T. 2009. "Phalacrocorax carbo" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phalacrocorax_carbo.html
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Morphology

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Great cormorants are 84 to 90 cm long, with wingspans of 130 to 160 cm. They weigh from 2.6 to 3.7 kg. Males and females are similar in appearance, but males are 5 to 10% longer and up to 20% heavier. They have dark plumage overall, with a bluish gloss to it. Their wings are slightly more brown and their face and gular region are yellow, bordered with small, white feathers. In the breeding season their heads and necks develop short, white plumes interspersed in their dark plumage. They also develop a white patch on each thigh. During egg-laying adults develop a small yellow to scarlet patch behind and below each eye. Immature individuals may be more brown or mottled in appearance. African great cormorants tend to have extensive white portions of their head and neck.

Great cormorants co-occur with other species of cormorant throughout most of their range, except for Greenland. In eastern North America they may be confused with the more abundant double-crested cormorants (Phalacrocorax auritus), which they commonly roost and nest near. Great cormorants are overall larger and have more white on their head and neck. Great cormorants are easily confused with European shags (Phalacrocorax aristotelis) in Europe.

Great cormorants vary in size and plumage throughout their range. In general, Asian and African populations are smaller than Palearctic and North American populations. The amount of white plumes on the head and neck, the color of skin on the head, and the color of the sheen on the black plumage varies substantially, but the pattern of variation has not been completely described. There are from 6 to 8 subspecies described: P. c. sinensis in Eurasia, P. c. hanedae in the Sea of Japan, P. c. novaehollandiae in Australia and New Zealand, P. c. maroccanus in northwestern Africa, and P. c. lucidus in the remainder of Africa.

Great cormorant resting metabolic rates have been estimated at 3.1 watts per kg. They are able to maintain their body temperatures in cold water and begin to use gular fluttering to lose heat when temperatures go above 20 degrees Celsius.

Range mass: 2.6 to 3.7 kg.

Range length: 84 to 90 cm.

Range wingspan: 130 to 160 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: male larger

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Dewey, T. 2009. "Phalacrocorax carbo" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phalacrocorax_carbo.html
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Life Expectancy

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The oldest wild great cormorant recorded was 22 years old, although it is expected that most do not live beyond 15 years old. After the first year, yearly survival rates are relatively high, approximately 72% in one study and up to 80% for adults in the same study. Most reported mortality in adults is from entanglement in fishing gear or being shot. Young typically die from exposure, predation, starvation, and falling from nests on cliffs.

Range lifespan
Status: wild:
22 (high) years.

Typical lifespan
Status: wild:
15 (high) years.

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Dewey, T. 2009. "Phalacrocorax carbo" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phalacrocorax_carbo.html
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Habitat

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Great cormorants are found in shallow, aquatic habitats, such as the coasts of oceans and large lakes and rivers. In North America, great cormorants are strongly associated with marine coastlines, in contrast to their smaller cousins, double-crested cormorants. In Europe, great cormorants are also found in inland, freshwater areas and in coastal estuaries. Nesting habits may vary among subspecies. North American great cormorants (P. c. carbo) nest mainly along coasts. Eurasian subspecies (P. c. sinensis) nest in inland areas, but the two subspecies sometimes occur in nesting colonies together in areas of recent overlap (British Isles).

Habitat Regions: temperate ; tropical ; saltwater or marine ; freshwater

Aquatic Biomes: lakes and ponds; rivers and streams; coastal

Other Habitat Features: estuarine

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Dewey, T. 2009. "Phalacrocorax carbo" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phalacrocorax_carbo.html
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Distribution

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Great cormorants are one of the most widespread of cormorant species, with a cosmopolitan distribution. Great cormorants are found throughout Europe, Asia, Africa, Australia, and in northeastern coastal North America. Populations in the western Atlantic and Europe have increased, with some range expansion, in the last 50 years.

Biogeographic Regions: nearctic (Native ); palearctic (Native ); oriental (Native ); ethiopian (Native ); australian (Native )

Other Geographic Terms: cosmopolitan

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Dewey, T. 2009. "Phalacrocorax carbo" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phalacrocorax_carbo.html
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Trophic Strategy

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Great cormorants eat almost exclusively fish less than 20 cm in length. They occasionally eat larger fish, up to 75 cm long or 1.5 kg. Some crustaceans are also eaten rarely. Fish are taken mostly in shallow water less than 20 m deep, but they hunt throughout the water column, from the surface to the bottom, depending on the prey. They dive in and pursue fish under the water using vision, eating small fish underwater and bringing larger fish to the surface to swallow. Great cormorants may also follow fishing boats, taking fish discards or capturing prey disturbed by the wake of a boat. Great cormorants may forage alone or in flocks, varying regionally and possibly with subspecies.

Great cormorants eat a wide variety of fish species, but may rely primarily on only a few species that are abundant locally, often bottom-dwelling species. In areas where cormorant species co-occur, they may pursue slightly different kinds of prey. In areas where great cormorants co-occur with double-crested cormorants, they eat more bottom-dwelling fish.

Great cormorants will drink sea water and can rid themselves of excess salt through their salt glands. Adults bring chicks water when they are heat stressed.

Animal Foods: fish; aquatic crustaceans

Primary Diet: carnivore (Piscivore )

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Dewey, T. 2009. "Phalacrocorax carbo" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phalacrocorax_carbo.html
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Associations

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Great cormorants nest in mixed-species colonies with other cormorants, gulls, and kittiwakes. Great cormorants are susceptible to Newcastle disease and avian influenza and are parasitized by nematodes (Contracaecum rudolphii) and 11 species of trematodes.

Mutualist Species:

  • double-crested cormorants (Phalacrocorax auritus)
  • other cormorant species (Phalacrocorax)
  • gulls (Larus)
  • kittiwakes (Rissa)

Commensal/Parasitic Species:

  • nematodes (Contracaecum rudolphii)
  • trematodes (Trematoda)
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Dewey, T. 2009. "Phalacrocorax carbo" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phalacrocorax_carbo.html
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Benefits

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Great cormorants are hunted for sport and are eaten in some areas. Most interestingly, great cormorants are tamed by humans to use to catch fish. This is an ancient practice in east Asia, dating back to the 5th century in China, and is still practiced in China and Japan. In other areas they are sometimes tamed and used in a similar way as a sport. Tamed great cormorants were used for fishing in England and France in the 17th and 19th centuries. A ring or other obstruction is placed around the cormorant's neck so that the fish can capture, but not swallow, a fish. The birds are harnessed and a leash is used to recall them, at which point the fish is removed from the throat. Some great cormorants have been reported to be so well trained as to not need the strap. They simply don't swallow the fish until the 8th fish, which they are allowed to eat. This suggests the potential that they can "count." Great cormorants with clipped wings have also been used on Djoran Lake (between Yugoslavia and Greece) to drive fish into nets.

Positive Impacts: food

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Dewey, T. 2009. "Phalacrocorax carbo" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phalacrocorax_carbo.html
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Conservation Status

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Great cormorants are widespread and populations are large, although surveys across their range are not complete. Populations have declined in the past, often as a result of human persecution, especially from commercial fishing. Recoveries from declines have been variable, with some populations remaining at lower levels and some recovering. In general, population increases may be most directly associated with prey availability. They are considered "least concern" by the IUCN.

US Migratory Bird Act: protected

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

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Dewey, T. 2009. "Phalacrocorax carbo" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phalacrocorax_carbo.html
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Untitled

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Great cormorants are considered most closely related to Japanese cormorants (Phalacrocorax capillatus). Some researchers place these two species as the only species in Phalacrocorax, with other cormorant species being placed in other genera.

"Phalacrocorax" is Greek, meaning "bald raven" and "carbo" is Latin for charcoal. Great cormorants are also called European cormorants, black cormorants, black shags, white-breasted cormorants, and common cormorants. They are also sometimes called "shags," but this does not discriminate among other species of Phalacrocorax.

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Dewey, T. 2009. "Phalacrocorax carbo" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phalacrocorax_carbo.html
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Behavior

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Great cormorants use a wide variety of hoarse calls. Males tend to have louder calls than females. Call types include threat calls ("tok-gock-gock"), calls associated with a kink-throating behavior ("curr-curr-curr"), calls associated with hopping ("ah-ah-ah" or "fi-fi-fih"), calls after landing or hopping ("roor"), gargling calls ("fee-he-he-he"), and calls when individuals entwine necks ("rrr"). They produce other sounds associated with courtship behaviors as well. Visual displays are used nest territory defense. Threat postures are when great cormorants hold their bodies horizontally, with their wings spread slightly and the tail fanned, the mouth is held open and the head is moved from side to side. During these threat displays males make a hoarse call and females make a soft huffing sound. Nest territory displays might also involve grabbing a piece of nesting material and shaking it.

Communication Channels: visual ; acoustic

Perception Channels: visual ; tactile ; acoustic ; chemical

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Dewey, T. 2009. "Phalacrocorax carbo" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phalacrocorax_carbo.html
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Reproduction

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Male great cormorants choose and defend a nesting territory. Pairs are monogamous and pairs may be reunited in subsequent years, with 11% of pairs remaining together over several years in one study. Males use a wing-waving display to attract females to their nest site; they raise their wing-tips up and out, alternately hiding and exposing white patches on their thighs while they do this. Once a pair has been formed, they greet each other with a gargling display. Male gargling displays are more exaggerated and involve lifting the head, opening the mouth, then dipping the head back towards the tail while waving it back and forth and making a gargling noise. Mated individuals also preen each other, entwine their necks, and performing several other displays in specific contexts (pointing, preflight, postlanding, hop, and kin-throat). Extra-pair copulations have been estimated at up to 16% in some colonies.

Mating System: monogamous

Great cormorant pairs may return to the same nest site year after year if they were successful breeding at that site before. They nest in large colonies, often with other species, including cormorants, gulls, and kittiwakes. Colony sizes vary regionally and with subspecies, from a mean of 117 nests to over 9000. The timing of breeding also varies substantially throughout the range of great cormorants. Colonies in warmer areas breed earlier than those in colder areas. In the tropics they may breed year-round or breed in wet seasons. In North America, great cormorants arrive at breeding colonies in late February and early March and begin to form pairs. A single clutch is laid from late April to early July, although clutches laid after June are often abandoned. If a clutch is lost early in the year, parents will attempt to re-nest. Young are fledged and nesting colonies are deserted by the middle of August. Nests are either on the ground or in trees and are made of sticks and seaweed lined with grass and feathers. Females lay 1 to 7 (typically 3 to 5) chalky, bluish green eggs and begin to incubate them gradually. Eggs hatch 28 to 31 days after incubation begins. Young fledge at 45 to 55 days after hatching and leave the nest soon after that. They join communal roosting areas and are continued to be fed by parents for another 2 to 3 months after fledging. Young males and females typically begin to breed at 3 years old (range 2 to 4 years).

Breeding interval: Great cormorants breed once a year, generally laying a single clutch.

Breeding season: The timing of breeding varies regionally and with subspecies.

Range eggs per season: 1 to 7.

Average eggs per season: 3 to 5.

Range time to hatching: 28 to 31 days.

Range fledging age: 45 to 55 days.

Range time to independence: 105 to 145 days.

Range age at sexual or reproductive maturity (female): 2 to 4 years.

Range age at sexual or reproductive maturity (male): 2 to 4 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous

Both parents incubate and feed their young. Parents incubate the eggs between their feet and breasts, taking approximately equal incubation shifts. Great cormorant hatchlings are naked and blind at hatching, developing a coat of down by 6 days old. Both parents brood them for about 10 days and at least 1 parent is at the nest until the young are 2 weeks old. Parents then begin to visit the nest primarily for feeding. Parents also help to cool hatchlings by shading them or bringing water. Hatchlings are fed by both parents through regurgitation. As parents approach, the hatchlings beg vigorously and food is deposited in their mouths when they are small. As they develop, they begin to insert their heads into their parents mouth to gather regurgitate from the parent's pharyngeal pouch. Older hatchlings begin to compete in the nest and stronger hatchlings may be fed more. The smallest hatchling often dies within a few weeks, but survival of other young is generally high. After fledging, the young continue to be fed by their parents for 2 to 3 months. Nest colonies are generally abandoned by all birds by the time the young are 70 to 90 days old. Young gather in creches after they leave the nest and parents recognize their young in those aggregations.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female)

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Dewey, T. 2009. "Phalacrocorax carbo" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phalacrocorax_carbo.html
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Biology

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Coastal cormorants make their nest on rocky ledges or islands out of seaweeds; inland tree-nesting birds construct their nest from twigs. The faeces are so acidic that nest-trees usually die within about three years (3). Either 3 or 4 pale blue, chalky eggs are laid, these are incubated for 28-31 days during which time they are placed on the adult's feet and warmed by the body (3). In the first few days of life the chicks feed on liquid regurgitated by the parents, they then take solid food from the parent's throats (3). After 50 days of life the young fledge, and return to the colony to breed at 2-3 years of age (3). During the winter, they roost together each evening, sometimes in their hundreds (9). Cormorants feed exclusively on fish (6), which are caught by means of dives from the surface of the water (6). A wide range of fish is taken, and this bird's efficiency as a predator has brought it into conflict with anglers (3). The cormorant has special feathers, which allow the water to penetrate, enabling the bird to swim well under water. After fishing, cormorants stand in a characteristic pose, with wings out and neck extended (3). This was thought to be to dry their wings, but is now considered to help digestion (9).
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Conservation

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Like all birds, the cormorant receives protection under the Wildlife and Countryside Act of 1981; it is illegal to kill wild birds and their nests and eggs cannot be taken or destroyed (5).
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Description

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This large water bird has a long neck, giving it something of a primitive, reptilian appearance (3). Adults are black with a bluish or green sheen. At the base of the bill is an area of bare, yellow skin surrounded by white (1). During the breeding season there is a white patch on the thigh, and throughout the year a variable amount of white occurs on the crown and back of the neck (1). Juveniles are dark brown and have a white area on the underparts (1). A variety of deep vocalisations are produced in colonies (1). The name cormorant is derived from the Latin 'corvus marinus', which means 'sea crow' (4).
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Habitat

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Coastal populations occur in shallow inshore marine waters (6) where there are rocky islands or cliffs (3). Inland colonies nest in trees close to freshwater lakes, reservoirs and gravel pits (3), and these are increasing (5).
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Range

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This bird occurs around the coastline of Great Britain, but is absent from much of north east Scotland (3). Although typically thought of as a sea bird, inland breeding colonies do occur, these are now increasing after being largely wiped out due to persecution since medieval times (5). Globally this is a very widespread species, occurring in most temperate areas of the Old World (6).
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Status

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Receives general protection under the Wildlife and Countryside Act 1981, and listed under Appendix III of the Bern Convention. Classified as a species of conservation concern by the UK Biodiversity Action Plan, although not a priority species (2). Included in the Birds of Conservation Concern Amber List (medium conservation concern) (8).
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Threats

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People involved in angling and fisheries are concerned that the increase in numbers of cormorants in the UK is having a negative impact on fish stocks (5), and some are calling for the legal protection of the species to be reduced (3). Conservationists believe that any conflicts can be resolved on each site and are worried that such a move would affect the conservation status of the species (5).
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Status in Egypt

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Regular passage visitor and winter visitor.

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Brief Summary

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Great cormorants eat fish and are known for their excellent diving skills. They forage in fresh as well as saline or brackish water. They can rotate their eyes, something most other birds are unable to do. Unlike other water fowl, their plumage is not oily. They absorb lots of water, so they need to spread their wings to dry after a swim. This bird has not had an easy life in the Netherlands. Because it was considered a rival for fishermen, they were shot, poisoned, chased away and even hung in huge numbers,
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Great cormorant

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

The great cormorant (Phalacrocorax carbo), known as the 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.[2] The genus name is Latinised Ancient Greek, from φαλακρός (phalakros, "bald") and κόραξ (korax, "raven"), and carbo is Latin for "charcoal".[3]

It breeds in much of the Old World, Australia, and the Atlantic coast of North America.

Taxonomy and etymology

The 80–100 cm (30–40 in) 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. Sibley & Monroe 1990, Sinclair, Hockey & Tarboton 2002).

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), 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 name; "kawau".[4] The syntype is in the collection of the Museum of New Zealand Te Papa Tongarewa.[5]

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 1.5 kg (3 lb 5 oz)[6] to 5.3 kg (11 lb 11 oz).[7] 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).[8] The lightest average weights cited are in Germany (P. c. sinensis), where 36 males averaged 2.28 kg (5 lb 12 oz) and 17 females averaged 1.94 kg (4 lb 4+12 oz).[9] The highest come from Prince Edward Island in Canada (P. c. carbo), where 11 males averaged 3.68 kg (8 lb 2 oz) and 11 females averaged 2.94 kg (6 lb 7+12 oz).[10][11] Length can vary from 70 to 102 cm (27+12 to 40 in) and wingspan from 121 to 160 cm (47+12 to 63 in).[11][12] 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 are scarcely smaller at average.[9] 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 by its larger size, heavier build, thicker bill, lack of a crest and plumage 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. 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, 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, Iceland and Greenland; and on the eastern seaboard of North America. The subspecies P. c. novaehollandiae is found in Australian waters.[4]

Behaviour

Diving in Dambovita River,Bucharest
Diving in Dambovita River,Bucharest
Great cormorant with bronze featherback from Keoladeo Ghana National park, Bharatpur
Great cormorant trying to swallow bronze featherback. from Keoladeo Ghana National park, Bharatpur
Great cormorant (Phalacrocorax carbo) from Ponnani Malappuram Kerala India

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.[13]

This cormorant lays a clutch of three to five eggs that measure 63 by 41 millimetres (2+12 by 1+58 in) 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.[13]

Feeding

The great cormorant feeds on fish caught through diving.[13] This bird feeds primarily on wrasses, but it also takes sand smelt, flathead and common soles.[14] 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.[15] 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).[16]

This cormorant forages by diving and capturing its prey in its beak.[13] The duration of its dives is around 28 seconds, with the bird diving to depths of about 5.8 metres (19 ft 0 in). 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.[14] Studies suggest that their hearing has evolved for underwater usage, possibly aiding their detection of fish.[17] These adaptations also have a cost on their hearing ability in air which is of lowered sensitivity.[18]

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).[19] Increasing populations have once again brought the cormorant into conflict with fisheries.[20][21] 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.

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.

In Norway, the cormorant is a traditional game bird. Each year approximately 10,000 cormorants are shot to be eaten.[22] 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

Videos

References

  1. ^ BirdLife International (2019). "Phalacrocorax carbo". IUCN Red List of Threatened Species. 2019: e.T22696792A155523636. doi:10.2305/IUCN.UK.2018-2.RLTS.T22696792A155523636.en. Retrieved 13 November 2021.|date= / |doi= mismatch
  2. ^ Ali, S. (1993). The Book of Indian Birds. Bombay: Bombay Natural History Society. ISBN 978-0-19-563731-1.
  3. ^ Jobling, James A (2010). The Helm Dictionary of Scientific Bird Names. London: Christopher Helm. pp. 90, 301. ISBN 978-1-4081-2501-4.
  4. ^ a b Heather, Barrie; Robertson, Hugh (2005). The Field guide to the Birds of New Zealand (revised ed.). Viking. ISBN 978-0143020400.
  5. ^ "Phalacrocorax carbo novaehollandiae; syntype". Collections Online. Museum of New Zealand Te Papa Tongarewa. Retrieved 18 July 2010.
  6. ^ Ribak, Gal; Weihs, Daniel; Arad, Zeev (2005). "Water retention in the plumage of diving great cormorants Phalacrocorax carbo sinensis". Journal of Avian Biology. 36 (2): 89. doi:10.1111/j.0908-8857.2005.03499.x.
  7. ^ "Cormorant". The Canadian Encyclopedia. Retrieved 21 August 2012.
  8. ^ Koffijberg, K.; Van Eerden, M.R. (1995). "Sexual dimorphism in the cormorant Phalacrocorax carbo sinensis: possible implications for differences in structural size" (PDF). Ardea. 83: 37–46.
  9. ^ a b Dunning Jr., John B., ed. (1992). CRC Handbook of Avian Body Masses. CRC Press. ISBN 978-0-8493-4258-5.
  10. ^ Hogan, G. (1979). Breeding parameters of Great Cormorants (Phalacrocorax carbo) at mixed species colonies on Prince Edward Island, Canada (Master's Thesis). St. Catharines, ON: Brock University. hdl:10464/1789.
  11. ^ a b Hatch, Jeremy J.; Brown, Kevin M.; Hogan, Geoffrey G.; Morris, Ralph D. (2000). Poole, A. (ed.). "Great Cormorant (Phalacrocorax carbo)". The Birds of North America Online. Ithaca: Cornell Lab of Ornithology. doi:10.2173/bna.553.
  12. ^ Stevenson, Terry; Fanshawe, John (2001). Field Guide to the Birds of East Africa: Kenya, Tanzania, Uganda, Rwanda, Burundi. Elsevier Science. ISBN 978-0-85661-079-0.
  13. ^ a b c d Hauber, Mark E. (1 August 2014). The Book of Eggs: A Life-Size Guide to the Eggs of Six Hundred of the World's Bird Species. Chicago: University of Chicago Press. p. 132. ISBN 978-0-226-05781-1.
  14. ^ a b Grémillet, D.; Argentin, G.; Schulte, B.; Culik, B. M. (2008). "Flexible foraging techniques in breeding cormorants Phalacrocorax carbo and shags Phalacrocorax aristotelis: benthic or pelagic feeding?". Ibis. 140 (1): 113–119. doi:10.1111/j.1474-919X.1998.tb04547.x. ISSN 0019-1019.
  15. ^ Čech M., Čech P., Kubečka J., Prchalová M., Draštík V. (2008). "Size selectivity in summer and winter diets of great cormorant (Phalacrocorax carbo): Does it reflect season-dependent difference in foraging efficiency?". Waterbirds. 31 (3): 438–447. doi:10.1675/1524-4695-31.3.438. JSTOR 25148353. S2CID 84199917.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  16. ^ Čech M., Vejřík L. (2011). "Winter diet of great cormorant (Phalacrocorax carbo) on the River Vltava: estimate of size and species composition and potential for fish stock losses". Folia Zoologica. 60 (2): 129–142. doi:10.25225/fozo.v60.i2.a7.2011. S2CID 90464667.
  17. ^ "Surprising hearing talents in cormorants". ScienceDaily. Retrieved 2020-10-08.
  18. ^ Larsen, Ole Næsbye; Wahlberg, Magnus; Christensen-Dalsgaard, Jakob (2020-03-15). "Amphibious hearing in a diving bird, the great cormorant ( Phalacrocorax carbo sinensis )". The Journal of Experimental Biology. 223 (6): jeb217265. doi:10.1242/jeb.217265. ISSN 0022-0949. PMID 32098879. S2CID 211524892.
  19. ^ "Cormorants in the western Palearctic, Distribution and numbers on a wider European scale" (PDF). Wetland International Cormorant Research Group. Archived from the original (PDF) on 7 June 2011.
  20. ^ "Workshop on a European Cormorant management Plan, 20–21 November 2007" (PDF). EIFAC, European Inland Fisheries Advisory Commission.
  21. ^ "European Parliament resolution". 4 December 2008. on the adoption of a European Cormorant Management Plan to minimise the increasing impact of cormorants on fish stocks, fishing and aquaculture
  22. ^ "Reducing the conflict between Cormorants and fisheries on a pan-European scale" (PDF). Final Report. REDCAFE. p. 12. Around 10,000 adult Cormorants (of the 'Atlantic' carbo race) are hunted legally as game in Norway outside the breeding season.
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Great cormorant: Brief Summary

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

The great cormorant (Phalacrocorax carbo), known as the 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. The genus name is Latinised Ancient Greek, from φαλακρός (phalakros, "bald") and κόραξ (korax, "raven"), and carbo is Latin for "charcoal".

It breeds in much of the Old World, Australia, and the Atlantic coast of North America.

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Description

provided by World Register of Marine Species
Length: 80-100 cm. Plumage: generally black with a greenish gloss; cheeks, throat to upper breast white; thigh patches white when breeding. Immature blackish-brown above, off-white below. Bare parts: iris green; lores orange in male, scarlet in female; bill grey--darker above; gular pouch olive to dark green; feet and legs black. Immature with yellow gular pouch. Habitat: marine and inland waters, coastal estuaries.

Reference

Brown, L.H., E.K. Urban & K. Newman. (1982). The Birds of Africa, Volume I. Academic Press, London.

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Distribution

provided by World Register of Marine Species
semi-cosmopolitan

Reference

van der Land, J. (ed). (2008). UNESCO-IOC Register of Marine Organisms (URMO).

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Jacob van der Land [email]

Distribution

provided by World Register of Marine Species
North America; Oceania; range extends from Newfoundland to southern North Carolina

Reference

North-West Atlantic Ocean species (NWARMS)

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Kennedy, Mary [email]