Black-headed gull
| Black-headed gull | ||||||||||||
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Swimming brown-headed gull in breeding dress |
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| Chroicocephalus brunnicephalus | ||||||||||||
| ( Jerdon , 1840) |
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The brown-headed gull ( Chroicocephalus brunnicephalus , syn .: Larus brunnicephalus ) or Tibetan black-headed gull is a species of seagull that breeds on mountain lakes in southern Central Asia . The occurrence is concentrated in the highlands of Tibet at altitudes between 3000 and 4500 m. The wintering areas are on the coasts of the Indian subcontinent , Sri Lanka and the continental Southeast Asia .
description
With a body length of 41–43 cm and a wingspan of 105–115 cm, the black-headed gull is larger than the very similar black-headed gull , with which it also occurs in the wintering areas. The weight is between 450 and 714 g. The species is also more compactly built, with a flatter crown, a stronger beak and longer legs. Its habitus reminds in some ways of a thin-billed gull . The wings appear longer than those of a black-headed gull and show a more rounded tip; the flight seems slower. The sexes do not differ. The birds are fully colored in the second summer.
Adult birds
Adult birds in breeding dress show a brown head cap, which is slightly lightened in the face and turns blacker towards the back. This can form an almost black border in the worn plumage. In contrast to the black-headed gull, the iris is yellowish white; the eye is lined with white lids. The bill, legs and feet are dark brownish-red to wine-red in color. The back of the head, neck and neck are pure white like the underside and the tail. The top is light gray, but overall darker than that of the black-headed gull. The hand wing pattern shows the typical white triangle on the front edge of the genus; the wing tip is much more extensive black than that of the black-headed gull. Towards the inner part of the hand wing, the black part of the wing tip forms an arched edge and ends roughly on the fourth hand wing. On the two outer wings of the hand there are wide white subterminal fields that form a striking mirror.
The brown head cap is missing in the winter dress. In front of the eye and on the back of the ear covers there are dark spots that run out towards the crown of the head. These parts are less extensive than in the black-headed gull. Bill and legs are bright red; the tip of the beak is black.
Youth dresses
The youth dress is similar to that of the black-headed gull. The skull and back are spotty gray-brown; small and medium-sized arm covers are dark brown and appear scaly due to the wide white hems. The large arm covers are gray and sometimes have darker shaft strokes. The wing tip is black, the hand wing is lightened in an arc-like shape in white; the inner wings show white tips. On the white hand covers there is a streaky black pattern towards the distal part. The arm wings are brown-black with a white lace border. The dark wing is lined with white. The white tail shows a wide black subterminal band. The eye ring is black; the iris is initially dark. It brightens up well into winter. The orange-red beak has a black tip; the legs and feet are orange to brownish.
In the first winter, the head and back are already colored like adult birds. In the first summer, the top is already completely gray, but the wings of the youth dress are still largely preserved. There are still black markings in the area of the wing bow. These, like the remains of the dark tail band, can be preserved in the second winter.
Distribution and existence
The distribution area of the black-headed gull extends between Turkestan and the west of Xinjiang eastward to the southeast of Gansu . To the south it extends into the Pamirs , Ladakh and Tibet . The altitude distribution is between 3000 and at least 4500 m.
There are no estimates of the total stock. The species is probably not uncommon, as swarms of several hundred specimens often occur in the wintering areas. Due to the size of its distribution area, it is classified as 
(= Least Concern - not endangered).
About 1000 pairs breed in the Pamirs in Tajikistan . In a 2008 water bird census in Changthang , the species was found in 31 of 48 lakes. The population there was 11,621 individuals.
hikes
The black-headed gull is predominantly a migratory bird that migrates south between August and October. Individual specimens remain in the vicinity of the breeding areas such as in Nepal , Tibet or in western Yunnan , but most overwinter on the coasts of the Indian Ocean west to Pakistan , on the Gulf of Thailand and the South China Sea , north to the Gulf of Tonkin . Occasionally the species reaches the Arabian Peninsula , Hong Kong or the Maldives . It can also be found in smaller numbers along the major rivers such as the Brahmaputra . The return home begins in late March, reaches Nepal in April and southern Tibet in mid-May. Annual birds have been identified as oversummer in Bukhara . The westernmost proof of being a random visitor was found in Eilat in Israel .
nutrition
The black-headed gull feeds primarily on fish, crustaceans and fishery waste, plus insects and their larvae, earthworms and snails, and occasionally small rodents and plant-based food. Where fish are scarce, such as on Karakul in Tajikistan, arthropods such as caddis flies and amphipods make up a large proportion the food. Food is often sought for wading in shallow water; Insects are sometimes caught from the air. In winter quarters, the species follows fishing cutters out to sea.
Reproduction
The black-headed gull breeds on islands in large, cold mountain lakes with variable salinity or in adjacent swamp areas. The breeding colonies are occupied in May, the egg-laying begins at the end of May and reaches its peak at the beginning of June. At this time, the lakes can still be frozen over. The colony size is between about 50 and several thousand pairs. The nest distance is often only small. The species is not infrequently associated with the common tern .
The nest is a collection of plant stems. In swamps it can be very large, in the countryside it is generally smaller. The clutch consists of 1–4, but mostly 3 eggs. The nestlings are up to the tenth day through, only at night from the fourteenth day brooded . Older boys are also often at risk of dying in night frosts.
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. 418-427
- 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 , p. 617.
- Gerald S. Tuck, Hermann Heinzel : The sea birds of the world. Paul Parey Publishing House, Hamburg / Berlin 1980, ISBN 3-490-07818-7 .
Web links
- Larus brunnicephalus in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2009. Accessed on 1 February 2012 found.
- BirdLife International: Species Factsheet - Brown-headed Gull ( Larus brunnicephalus ) . Retrieved February 1, 2012.
- Videos, photos and sound recordings of Larus brunnicephalus in the Internet Bird Collection
- Photos of Larus brunnicephalus in the Oriental Bird Club image database , accessed February 1, 2011
Individual evidence
- ↑ Olsen / Larsson (2003), see literature
- ↑ Zhang Guo-gang, Liu Dong-ping, Jiang Hong-xing, Zhang Ke-jia, Zhao Huai-dong, Kang Ai-li, Liang Hai-tang, Qian Fa-wen: Abundance and Conservation of Waterbirds Breeding on the Changtang Plateau, Tibet Autonomous Region, ChinaFull Access , Waterbirds 38/1, March 2015, pp. 19–29, doi : 10.1675 / 063.038.0104