Great Cormorant
2007 Schools Wikipedia Selection. Related subjects: Birds
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| Phalacrocorax carbo Linnaeus, 1758 |
The Great Cormorant (Phalacrocorax carbo) is a widespread member of the cormorant family of seabirds. It breeds in much of the Old World and the Atlantic coast of North America.
Description
The Great Cormorant is a large black bird, 77-94 cm in length with a 121-149 cm wingspan. It has a longish tail and yellow throat-patch. Adults have white thigh patches 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.
The subspecies found in Australasian waters, P. carbo novaehollandiae, has a crest. In New Zealand this is known as the Black Shag; another subspecies, the White-breasted Cormorant P. c. lucidus found in sub-Saharan Africa, has a white neck and breast.
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.
The type subspecies, P. c. carbo, is found mainly in Atlantic waters and nearby inland areas: on western European coasts and south to North Africa, the Faeroes, Iceland and Greenland; and on the eastern seaboard of North America, though in America it breeds only in the north of its range, in the Canadian maritime provinces. In addition to the Australasian and African forms, Phalacrocorax carbo novaehollandiae and P. carbo 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. hannedae (Japan). Some authors treat all these as allospecies of a P. carbo superspecies group.
Behaviour
The Great Cormorant breeds mainly on coasts, nesting on cliffs or in trees (which are eventually killed by the droppings), but also increasingly inland. 3-4 eggs are laid in a nest of seaweed or twigs.
The Great Cormorant can dive to considerable depths, but often feeds in shallow water. It frequently brings prey to the surface. A wide variety of fish are taken: cormorants are often noticed eating eels, but this may reflect the considerable time taken to subdue an eel and position it for swallowing, rather than any dominance of eels in the diet. In UK waters, dive times of 20-30 seconds are common, with a recovery time on the surface around a third of dive time.
Cormorants and humans
Many fishermen see in the Great Cormorant a competitor for fish. Because of this it was nearly hunted to extinction in the past. Thanks to conservation efforts its numbers increased. At the moment there are about 450.000 breeding birds in West Europe.