Common Tern
Sterna hirundo Linnaens, 1758
Order Charadriiformes
Family Sternidae
Conservation status: in Bulgaria: Endangered
EN=[A{3(b+c)+B{1(a+b(i+ii+iii+iv)+C{2(a(i)} + E].
General distribution. A Holarctic species with a breeding area embracing Europe (without Portugal), Asia, Siberia, Northern America, the Caribbean Sea.
Distribution and abundance in Bulgaria. A breeding summer visitor and passage migrant. At the beginning of the 20th century it bred with large numbers along the Danube, the valley of the Maritsa River, near the towns of Pomorie and Sozopol, probably also near Sofia [5, 8, 9, 10, 14]. The major population after the 80s was concentrated in the Burgas wetlands, where it breeds on artificial islands and platforms [1-4, 6, 11, 13]. At present it breeds in 13 habitats, more important among which are: Atanasovsko Ezero lake, Pomoriysko Ezero lake, Poda Protected Locality, Zmiyskiya Ostrov island, the mouth of the Ropotamo River, islands and marshes of the Danube and some of the larger internal rivers [1-4, 13, 15]. In Srebarna Lake, 31 pairs bred in the 2005 period [16]. Two habitats are new: the oxygenation lakes of LUKOIL near Burgas (in 2003-2006 – 160-222 breeding pairs) and the tail of Poroy Reservoir, Burgas region (2003-2005, 12 – 24 breeding pairs) (K. Bedev, unpubl. data). The breeding population in Bulgaria is estimated at a maximum of 500-540 pairs [6, 7, 12]. According to other estimates, it is between 700 – 1 500 pairs [15].
Habitats. Various freshwater, brackish and supersalty natural and artificial wetlands.
Biology. It breeds in separate or in mixed colonies with the Little Tern, the Collared Pratincole, the Avocet, the Mediterranean Gull and the Black-headed Gull. The nest is situated in a hole in the ground formed by mussels, water plants and grasses. It feeds on fish, shrimps, insects [3].
Similar species. The Arctic Tern(Sterna paradisaea).
Negative factors. Flooding of the breeding colonies; destruction of the clutches and the nests with newly-hatched birds by hails and ground predators; disturbance; illegal shooting; destruction or excessive overgrowth of the breeding places; flooded areas by crude oil products.
Conservation measures taken. Protected according to the Biological Diversity Act. The major breeding places are in protected territories.
Conservation measures needed. Regulation of the numbers of the ground predators. Building nesting platforms and alluvial islands in the lakes Atanasovsko, Pomoriysko, the Poda Protected Locality and the oxygenation lakes of LUKOIL. Disallowing repairing activities of the dikes in the Pomorie and Burgas saltworks during breeding. The breeding places in oxygenation lakes of LUKOIL and the tail of Poroy Reservoir should be declared protected territories.
References. 1. Bedev et al., 1996; 2. Bedev et al., 1997; 3. Bedev et al., 1998; 4. Bedev et al., 1999; 5. Georgiev, 1976; 6. Kostadinova, 1997; 7. Nankinov et al., 2004; 8. Nankinov, Simeonov, Michev, Ivanov, 1997; 9. Patev, 1950; 10. Prostov, 1964; 11. Iankov, 2006; 12. BirdLife International, 2004; 13. Dimitrov et al., 2005; 14. Reiser, 1894. 15. Iankov, in press; 16. Kambourova, 2004.
Authors: Kiril Bedev, Milko Dimitrov
