Atlas of nesting birds in Bulgaria

Sandwich Tern

(Thalasseus sandvicensis)

Category of conservation concern (IUCN, 2020) – Least Concern

Population size: 2020: 1 300 -2 400 pairs (2007: 300 – 1 300 pairs)

Distribution pattern

Numerous species, but with strongly localized distribution. Inhabits mainly coastal hypersaline water bodies – coastal lagoons, saltpans, and others. Hunts only in salty or brackish waters, most often in the coastal parts of the sea.

Population estimation for the period 2013 – 2020:  During the period 2013-2020, no visible change in the distribution of the species was established with the exception of one accidental breeding site in the Mandra-Poda Complex. The only permanent breeding colony of the species is found on the territory of the Pomorie Lake, where the species increases in number. The main factor for this increase are the successful conservation measures implemented over the years in order to expand the area and improve the breeding habitat of the species.

Population size in Special Protection Areas of Natura 2000: 1 300-2 400 pairs (100% of the population). All the habitats of the species are found on the territory of the Natura 2000 network. The highest numbers have been registered in the Special Protection Areas “Pomoriysko Lake” (1300-2400 pairs), “Atanasovsko Lake” (0-120 pairs) and the “Mandra-Poda Complex” (0-2 pairs)

Big size map

Breeding distribution 2013 – 2020 – The distribution and the estimation of the population size of the species for the period 2013 – 2020 is presented –

Comparative distribution of the species compared to the first breeding birds atlas (Iankov, 2007): Breeding locality until 2007 | Breeding locality until 2007, confirmed after 2015 – | New breeding locality after 2015. – The breeding localities after 2015 are identified on a base of raw data from


Breeds in lagoons – saltpans with saltwater or in hypersaline water bodies. In natural conditions builds its nests on dividing dikes or other saline terrains with halophytic vegetation, but at present the whole population breeds on artificial platforms and gravel islands. A colonial breeding species, colonies can reach thousands of breeding pairs. Very often breeds in mixed colonies with other Terns and Plovers. The only breeding sites in our country are located in the Pomorie Lake and the Atanasovsko Lake. The location of the colonies is in close proximity to the coastal part of the sea – its forage area.

Trends in population changes for the period 2013-2020

Short-term trend of population size:


Long-term trend of population size:


Short-term trend of distribution:


Long-term trend of distribution:



Predation by terrestrial mammals, threatening eggs and chicks in breeding colonies. Disturbance during the breeding season by recreational activities (windsurfing) near the colony in the Pomorie Lake. Extreme climate events because of global climate change. Destruction of nests and chicks due to technical activities in the production and extraction of salt.

Vladimir Mladenov, Ralitsa Georgieva, Petar Shurulinkov