Black-headed Gull
Larus ridibundus Linnaeus, 1766
Chema ridibundum L.: Reiser, 1894: 199; Hydrocoleus ridibundus (L.): Boetticher, 1927: 197.
Order Charadriiformes
Family Laridae
Conservation status: in Bulgaria: Endangered EN [B1a+B2a+B2c(iv)+C2], BDA-III; International: BeC-III.
General distribution. A trans-Palearctic species whose breeding area embraces Newfoundland island, Greenland, Iceland, the Faroe Islands and the British Isles, the Scandinavian peninsula, Western and Central Europe, Spain, Italy, the former Yugoslavia, Bulgaria, Romania, Russia, Mongolia and China. The southern border of its breeding area passes through the territory of Bulgaria. Since 1987 it has also been breeding in Northern Greece. It winters in the western part of the Atlantic Ocean, around the Mediterranean and the Black Sea, the southern and the eastern shores of Asia, Africa and America.
Distribution and abundance in Bulgaria. A breeding summer visitor and wintering species, in the past it incubated in the Svishtov Swamp [1]. There were episodic breeding habitats in Atanasovsko Ezero lake and near the village of Chernomorets, Burgas region [2]. In 1963, a breeding colony of 120 pairs was found in Garvansko Marsh [3]. In the second half of the 20th century it bred only on Persina Island and in Srebarna Lake [4], where there was a colony with large numbers: between 300 and 500 pairs [3], between 5 and 40 pairs in 2001-2003 [5]. In both breeding habitats the numbers vary greatly during the years [6]. The breeding population in the country is estimated at 500-700 [7], 250-350 [8], 180-250 [9], but in recent years it has not exceeded 300 pairs. During migrations and wintering it is one of the most frequently observed and numerous species of gulls in the low parts of the country.
Habitats. Marshes and lakes with ample water vegetation. Outside the multiplication period: fish farms, reservoirs, canals, dumping grounds.
Biology. It breeds in independent or mixed colonies situated on floating root systems of reed, leaves of water lilies (Srebarna Lake, Garvansko Marsh) and sticking from the water stumps (Persina island). It lays 1-3 eggs. The young ones hatch at the end of May and the beginning of June. After the end of the breeding period, the young and adult birds wander in large flocks. They eat fish, shrimps, insects [3].
Similar species. The Mediterranean Gull (Larus melanocephalus).
Negative factors. Unknown. Most probably changes of the natural water regime in the traditional breeding habitats (Persina Island, Garvansko Marsh, Srebarna Lake).
Conservation measures taken. Protected according to the Biological Diversity Act. Included in the Red Data Book of Bulgaria (1985). Most of its habitats along the Danube are included in Protected Territories.
Conservation measures needed. Restoration of Garvansko Marsh; increase of the water supply in the marshes on Persina Island; study of the negative factors on the numbers of the breeding populations.
References. 1. Reiser, 1894; 2. Prostov, 1964; 3. Nankinov et al., 1997; 4. Ivanov, 1970; 5. Kambourova, 2004; 6. Ivanov, 1985; 7. Kostadinova, 1997; 8. Nankinov et al., 2004; 9. BSPB, in press.
Authors: Tanyo Michev, Nevena Kambourova
