Gray-headed gull
| Gray-headed gull | ||||||||||||
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Gray-headed gull in breeding plumage ( Senegal ) |
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| Chroicocephalus cirrocephalus | ||||||||||||
| ( Vieillot , 1818) |
The gray-headed gull ( Chroicocephalus cirrocephalus , syn .: Larus cirrocephalus ) is a medium-sized species of gull that occurs in several large and small areas that are scattered over Africa and South America .
description
With a body length of 39 to 42 cm, the gray-headed gull is larger and more powerful than a black-headed gull . The wingspan is 100–115 cm, the wing length in the adult male between 308 and 343 mm, in females between 290 and 328 mm. The weight can be between 211 and 388 g. The head is also larger than that of the black-headed gull, the forehead somewhat elongated, the beak stronger. In addition, the chest looks more arched, the wings longer and wider. Typical is an upright pose with the head raised and the tail lowered. In flight, the wings are often bent slightly; the flapping of the wings is relatively slow. The sexes do not differ. The birds are colored from the second or third year.
Adult birds
Adult birds in breeding plumage wear a gray head cap, which is bordered at the bottom by a dark border. The eyes appear somewhat staring due to the yellowish white iris and are surrounded by a red orbital ring. The beak is dark red and sometimes shows a black tip; Legs and feet are bright red. The white on the back of the head, neck and neck gradually merges into the middle gray on the upper side on the front back. This is a little darker than that of a black-headed gull. The underside, rump and tail are pure white. The upper wing is gray and shows the narrow, white triangle typical of the species on the front hand wing. The bases of the hand wings are white and protrude in an arc shape into the black of the wing tip, which is formed by wide subterminal fields that become smaller and taper towards the hand wing. On the two outer wings of the hand there is a striking white mirror in front of the tips. The lower wing is dark gray.
In the simple dress, the head is white except for a black ear mark and a faded spot on the eye. Blurred remnants of the head cap can be indicated and run across the crown of the head at the rear edge of the cap and above the eye. But some birds are almost entirely white-headed. The beak is light red to orange-red with a dark tip; Legs and feet are red to red-orange.
Youth dresses
The youth dress is similar to that of the black-headed gull, but shows a more indistinct head pattern and looks browner overall. The beak, legs and feet are flesh-colored to yellowish flesh-colored. The beak shows a dark tip. A brownish faded cap is indicated on the head on a white background, in which a dark ear mark and white eyelids stand out. The eye is surrounded by a reddish brown orbital ring, the iris is brown. Interrupted by a whitish neck band, the brownish tint continues on the neck, neck, sides of the chest and on the front back. The underside is whitish. The back looks scaled due to dark feather centers and light hems; the rump is light gray. The tail wears a narrow, dark subterminal band. The gray of the upper wing is interrupted by a brown arm cover field and brown bands on the edge of the medium and large arm covers. The front part of the hand wing is white. This contrasts with the dark wing, a dark band on the palm of the hand and the black, inwardly curved wing tip. The arm wings are black with a white lace border.
The first plain dress is similar to the youth dress. The head is largely white, like that of adult birds in simple dress. The lower neck is light gray except for the front back. The dark gray back is often still interspersed with individual feathers of the youth dress. The dark areas on the upper wing brighten. The beak is already dark reddish in color at the base, legs and feet are reddish brown.
In the second winter the birds are almost completely colored. Sometimes a dark iris is preserved. The beak, legs and feet are often even more dull than in adult birds. On the upper wing, a dark wing trailing edge is often still indicated due to the dark wing centers. The white mirror on the outer arm covers is often not quite as extensive as in adult birds.
distribution
The brood distribution of the gray-headed gull extends in numerous disjoint sub-areas across Africa and South America. In South America, one occurrence extends on the Pacific coast in Ecuador and Peru , a second on the Atlantic coast from central Brazil to the south of the Argentine province of Buenos Aires and inland along the Río Paraguay and the Paraná Basin south to Santa Fe . The African occurrences are very scattered, but are mainly concentrated in the area of the equator on coasts and rivers in Senegambia , between Ethiopia and Malawi , in southern Africa, on Madagascar , as well as in the area of the Great African Rift Valley , where the species, for example, on the Naivasha , breeds at the Manyara , Elmentaita , Nakuru and Turkana lakes .
Geographical variation and hybrids
Two subspecies are recognized, of which the nominate form is somewhat larger and lighter on top. In addition, the white mirror on the two outer hand wings is more extensive. The West African birds are on average larger than the East African birds.
- Chr. C. cirrocephalus Vieillot , 1818 - South America
- Chr. C. poiocephalus Swainson , 1837 - Africa
A hybrid of the gray-headed and hard-leaved gull was found in South America .
hikes
Many gray-headed gulls are resident birds or short-range migrants ; many birds that breed inland overwinter on the coast. However, some birds also cover longer distances of up to 2000 km. Birds from Natal were found both on the western route on the Atlantic coast and on the eastern route on the Indian Ocean. Similar dismigrations are also taking place on the South American Atlantic coast.
Larger gatherings of winter guests occur at large lakes such as Lake Chad , Lake Victoria and Lake Nakuru, where 8,000 birds were counted between January and February. In Senegambia, the species is found in large numbers on the coast between November and April.
The species was found as a stray visitor in Panama , Florida , Spain , Gibraltar , Israel and Egypt , on the Arabian Peninsula and on the Red Sea . One specimen seen in the UK was believed to be a refugee from prison.
Duration
The world population of this species is mostly estimated at less than 50,000 breeding pairs, sometimes it is also estimated at 130,000–1,000,000 adult birds. The largest populations are in Africa, where in Senegal, Kenya and Tanzania there are colonies with sometimes over 2500 breeding pairs. On the Musambwa Islands , three rocky islands on the western edge of Lake Victoria , 10,000 breeding pairs have been found, the winter population here is 100,000 birds. The South African population of around 200 breeding pairs in 70 colonies (as of the 1990s) seems to be increasing. The South American population comprises around 10,000 pairs that breed predominantly in Argentina and on the Atlantic coast. The inventory trend has appeared to be positive since the 1920s.
The IUCN regards the species as not threatened (“least concern”).
nutrition
The gray-headed gull feeds primarily on fish and various invertebrates . In winter, fishing debris, other litter, and dead fish play a role. In some places the species appears as a kleptoparasite of terns and cormorants . Eggs of flamingos , herons and cormorants are also eaten. Sometimes the species can be observed during shock diving , sometimes it collects small creatures from the surface of the water while swimming. Insects such as termites are caught from the air.
Reproduction
The breeding season of the gray-headed gull in western Africa is before the rainy season, i.e. between April and May; in Peru it begins in early May. It breeds in colonies, the nest distance of which can be between 1 and 100 m. The nest is on the ground, in the reeds - or papyrus - Bulten between halophytes such as Salicornia or floating plants ceiling built. It sometimes consists of a shallow hollow that is sparsely lined with grass or other parts of plants; sometimes it is also a bowl made of rushes or grasses. The clutch consists of 3 eggs in South America and 2–3 eggs in Africa.
literature
- Klaus Malling Olsen, Hans Larsson: Gulls of Europe, Asia and North America , Helm Identification Guides, Christopher Helm, London 2003 (corrected new edition from 2004), ISBN 978-0-7136-7087-5 , pp. 428–437
- Josep del Hoyo , Andrew Elliott, Jordi Sargatal (eds.): Handbook of the Birds of the World. Volume 3: Hoatzin to Auks. Lynx Edicions 1996, ISBN 978-84-87334-20-7 , pp. 613/614.
- Gerald S. Tuck, Hermann Heinzel: The sea birds of the world , Paul Parey publishing house, Hamburg / Berlin 1980, ISBN 3-490-07818-7
Individual evidence
- ↑ a b c d Olsen / Larsson (2003), p. 428, see literature
- ↑ a b Olsen / Larsson (2003), p. 435, see literature
- ↑ a b c d e Olsen / Larsson (2003), p. 428f, see literature
- ↑ a b c d e f Del Hoyo et al. (1996), see literature
- ↑ a b c d e f g Olsen / Larsson (2003), p. 434, see literature
- ↑ BirdLife Species Factsheet, see web links
- ↑ Musambwa Islands at BirdLife, accessed February 10, 2012
Web links
- Larus cirrocephalus in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2009. Retrieved on 7 February 2012 found.
- BirdLife International: Species Factsheet - Gray-headed Gull ( Larus cirrocephalus ) . Retrieved February 7, 2012.
- Videos, photos and sound recordings of Larus cirrocephalus in the Internet Bird Collection