Socotra cormorant
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Socotra cormorant ( Phalacrocorax nigrogularis ) |
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| Ogilvie-Grant & Forbes , 1899 |
The Socotra cormorant ( Phalacrocorax nigrogularis ) is a species of bird in the Phalacrocorax family within the cormorant family. The dark brown colored species colonizes the Gulf of Persia and the Gulf of Aden and breeds in only nine colonies on small islands off the coast. The Socotra cormorant feeds primarily on fish . The IUCN leads the species because of the threatening destruction of the habitat as endangered (" vulnerable ").
Appearance
Socotra cormorants reach a head-body length of 76 to 84 centimeters and a wingspan of 102 to 110 centimeters. The species shows a slight sexual dimorphism , the males are on average slightly larger than the females.
The very slender body of adult birds is feathered dark brown, legs and feet are black. Breeding birds have some white feathers behind the eye that form a horizontal line on the sides of the eye. There are also some white feathers on the neck during this time. After the breeding season , the animals molt these feathers. The dark gray beak is long and narrow compared to that of other cormorants. The skin at the base of the beak is slightly yellow in color. The iris is dark green in color.
Fledglings are gray-brown on the back and neck, and dirty white on the belly, chest and throat.
distribution and habitat
The range of the Socotra cormorant is limited to the waters between the Persian Gulf and the Gulf of Aden . Individual animals, which are occasionally sighted further south and east, are exceptional and do not colonize these areas permanently.
The species lives exclusively marine and avoids the inland; Estuaries are also not populated. Even the coast is only visited if there are no islands or rocks in the sea to rest. Only a few small, sandy islands in the range are used for breeding.
food
Small fish are the main component of the diet , but crabs and other invertebrates such as mussels and starfish are also eaten. Like all cormorants, the species prefers to catch its prey by diving by following and catching it while swimming underwater. Often several individuals join forces to hunt and look out for schooling fish from the air , which they then prey together.
Since the plumage of the Socotra cormorant absorbs water, it has to be dried after a dive. Like most cormorants, Socotra cormorants spread their wings and let the sun or wind dry their plumage.
Breeding biology
The breeding season is variable and usually begins in spring, but broods have been observed throughout the year. The individual colonies do not breed synchronously and start the breeding business at different times, largely independent of climatic conditions.
The species breeds in just nine large colonies of up to over a hundred thousand breeding pairs. The colonies lie on flat, stony and sandy islands off the coast. The nest is a hollow dug into the sand or gravel that is sparsely padded with algae and feathers.
The clutch consists of 2-4 eggs, from which naked young birds hatch after about 30 days. A white down dress grows first before the gray-brown youth dress grows.
Migratory behavior
Little is known about the migratory behavior of the species. When there is a lack of food, Socotra cormorants sometimes fly long distances to the open sea. Small groups or individual animals are rarely seen off the west coast of India and in the Red Sea , but directed migration behavior is not observed.
Systematics
As with all cormorants, the exact systematic position of the species is disputed. Some scientists put the species in the monotypic genus Leucocarbo , but this is not generally recognized. No subspecies are distinguished.
Hazard and protection
The IUCN lists the species as endangered (“ vulnerable ”). The reasons for the endangerment are the small distribution area and the small number of breeding colonies. These colonies are located in a region that is subject to intensive human use and whose infrastructure is being greatly expanded. This disrupts breeding colonies. In addition, many birds died as a result of oil spills as a result of the Gulf Wars .
literature
- Josep del Hoyo , Andrew Elliot, Jordi Sargatal : Handbook of the birds of the world. Volume 1: Ostrich to Ducks. Lynx Edicions, Barcelona 1992, ISBN 84-87334-10-5 .
Web links
- Phalacrocorax nigrogularis in the endangered Red List species the IUCN 2010. Posted by: BirdLife International, 2009. Accessed March 12, 2011th
- BirdLife Factsheet , accessed March 12, 2011
- Videos, photos and sound recordings of Phalacrocorax nigrogularis in the Internet Bird Collection