Gull-billed Tern

(Gelochelidon nilotica)

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

Population size: 2020: 0-110 pairs (2007: 2-8 pairs)

Distribution pattern

Irregularly breeding species in the country with very limited breeding sites and small population. Locally breeds on the Black Sea coast – mainly in the Atanasovsko and the Pomorie lakes. The distribution depends on the availability of hypersaline wetlands. Individual specimens can be seen during the summer at Shabla Tuzla and the Durankulak Lake, but no data about definite breeding exists.

Population estimation for the period 2013 – 2020: During the period 2013-2020, the species was established in all historically proven breeding sites of the species in the country. Until 2014, the species has no confirmed breeding habitats in the country for the previous 18 years. During the study period, the Gull-billed Tern was established to breed periodically in the Atanasovsko and Pomorie lakes. Because of the successfully implemented measures for protection from predatory mammals of the main breeding colonies in Atanasovsko Lake, in 2014 for the first time around 49-59 pairs of the species were breeding after a long period. Two years later, the country’s record number of 90-110 pairs was recorded at the same place.

Population size in Special Protection Areas of Natura 2000: 0-110 pairs (100% of the population). The entire breeding population of the species is on the territory of the Natura 2000 network. Breeds only in the SPAs “Atanasovsko Lake” (0-110 pairs) and “Pomorie Lake” (0-55 pairs).

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 smartbirds.org.

Habitats

Breeds in hypersaline wetlands – coastal lagoons, estuaries and saltpans, most often on the dividing dikes between the pools (saline terrains with halophytic vegetation), in rare cases near standing brackish waters. Breeds on sandy islands, silts, dikes and banks in wetlands located near open grasslands where birds hunt small vertebrates and insects. Colonial species that requires the presence of other species in the colony – in our country most often breeds in mixed colonies with the Sandwich Tern and Pied Avocet.

Trends in population changes for the period 2013-2020

Threats

Predation by stray dogs, jackals, yellow-legged gulls, threatening eggs and chicks in breeding colonies. 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