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 Colonie Cape Gannet, Birds Island, Lamberts Bay, South Africa
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| Morus capensis (Lichtenstein, 1823) |
The Cape Gannet (Morus capensis, originally Sula capensis) is a large seabird of the gannet family, Sulidae. Martin Heinrich Carl Lichtenstein ( January 10, 1780 - September 2, 1857) was a German Physician, explorer and Seabirds are Birds that have adapted to life within the marine environment Gannets are Seabirds in the family Sulidae, closely related to the boobies. The Bird family Sulidae comprises the Gannets and boobies. Both groups are medium-large coastal Seabirds that plunge-dive for fish
When seen in flight the snow-white body with the black tail, primaries and secondaries, and dark bill makes then easy to identify. At closer range the distinctive golden crown and nape, which gradually become white on the neck, are noticeable. On the other hand, the dark brown juveniles look completely black when seen in flight. Adults are about 84-94 cm long and have a 171-185 cm wingspan and weigh ca. 2600 g.
Their breeding habitat is restricted to southern Africa in three islands off Namibia and three islands off South Africa. Southern Africa is the Southernmost Region of the African Continent, variably defined by Geography or Geopolitics. Namibia, officially the Republic of Namibia, is a country in Southern Africa on the Atlantic coast The Republic of South Africa (also known by other official names) is a country located at the southern tip of the continent of Africa They normally nest in large and dense colonies on flat islands or on flat ledges of the steeply sloping Mercury Island off Namibia. Namibia, officially the Republic of Namibia, is a country in Southern Africa on the Atlantic coast The world population was estimated in 1996 to number about 340,000 birds, with 12% in Namibia and 88% in South Africa. Year 1996 ( MCMXCVI) was a Leap year starting on Monday (link will display full 1996 Gregorian calendar) Namibia, officially the Republic of Namibia, is a country in Southern Africa on the Atlantic coast The Republic of South Africa (also known by other official names) is a country located at the southern tip of the continent of Africa The largest colony of this bird, with over 140,000 birds, is found on Malgas Island, South Africa. The Republic of South Africa (also known by other official names) is a country located at the southern tip of the continent of Africa Several birds have occasionally been found breeding on offshore Australian islands, together with Australasian Gannets, although the Cape species is never represented by more than a few pairs. For a topic outline on this subject see List of basic Australia topics. The Australasian Gannet ( Morus serrator or Sula bassana, also Australian Gannet, Tākapu) is a large Seabird of the [2]
The non-breeding range of Cape gannets extends from the coastal waters off the Gulf of Guinea on the west coast of Africa, to Mozambique on the east coast. The Gulf of Guinea is the part of the Atlantic Ocean southwest of Africa. Mozambique, officially the Republic of Mozambique (Moçambique or República de Moçambique, ʁɛ'publikɐ d musɐ̃'bik is a country in southeastern Africa They seldom occur farther offshore than 100 km, though records of birds more than 200 km offshore exist for both the Atlantic and Indian Oceans. The Indian Ocean is the third largest of the world's Oceanic divisions covering about 20% of the water on the Earth 's surface
Gannet pairs may remain together over several seasons. They perform elaborate greeting rituals at the nest, stretching their bills and necks skywards and gently tapping bills together.
Cape Gannets begin breeding in August or September. Typically the clutch is a single bluish egg, which soon becomes soiled. Both parents are actively involved in the incubation process which lasts for 42 to 46 days until hatching. Gannets use their foot webs to incubate the egg. The foot webs, which are richly irrigated with blood vessels are wrapped around the egg.
The hatchling is black, naked and blind, it weighs only about 70 grams, but within three weeks its body mass is one third of that of an adult. At eight weeks the chick outweighs the adult, and this remains so until it becomes a fledgling at 95-105 days of age.
Cape Gannets are powerful fliers, using mainly a flap-gliding technique, which is more energy consuming than the dynamic-soaring favoured by albatrosses. Albatrosses, of the biological family Diomedeidae, are large Seabirds allied to the procellariids, Storm-petrels and Diving-petrels As all Sulids, they are fish-eating birds that plunge-dive from considerable height.
Numbers of Cape Gannets at the Namibian islands have declined considerably between 1956 and 2000 from 114,600 to 18,200 breeding pairs respectively, an 84% decrease in less than fifty years. Year 1956 ( MCMLVI) was a Leap year starting on Sunday (link will display full calendar of the Gregorian calendar. 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. This contrasts with the trends at the South African islands where numbers have increased about 4. 3 times during the same period, from 34,400 to 148,000 breeding pairs.
References
- ^ BirdLife International (2004). Morus capensis. 2006 IUCN Red List of Threatened Species. The IUCN Red List of Threatened Species (also known as the IUCN Red List or Red Data List) created in 1963 is the world's most comprehensive inventory of the global IUCN 2006. Retrieved on 11 May 2006. Database entry includes a range map and justification for why this species is vulnerable
- ^ Pizzey, Graham; Knight, Frank (2007). Graham Martin Pizzey AM ( 4 July 1930 - 12 November 2001) was a noted Australian Author, Photographer and The Field Guide to the Birds of Australia. HarperCollins, 102-03. HarperCollins is a Publishing company owned by News Corporation.
- Crawford 1997. Cape Gannet. In: The Atlas of Southern African Birds Vol. 1: Non-passerines. Harrison, J. A. Allan, D. G. , Underhill. L. G. , Herremans, M. , Tree, A. J. , Parker, V. & Brown, C. J. (eds), pp. 28-29. BirdLife South Africa, Johannesburg.
- du Toit, M. & Cooper, J. 2002. Cape Gannet. In: Proposal for inclusion of species in Annex 2 of the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA, an agreement under UNEP/CMS). Avian Demography Unit, Cape Town.
External links
- Cape Gannet Avian Demography Unit Fact sheets on Southern African seabirds
- ARKive - images and movies of the cape gannet (Morus capensis)
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