Whiskered tern - Chlidonias hybrida
A couple of Whiskered terns spotted over Aldomirovtsi marsh in Western Bulgaria. This migratory bird rarely can be seen inside the country. During the migration it can be seen along the Danube river and on the Black Sea coastline.
The whiskered tern is a seabird of the tern family, Sternidae. The genus name is from Ancient Greek ''khelidonios'', "swallow-like", from ''khelidon'', "swallow". The specific ''hybridus'' is Latin for ''hybrid''; Pallas thought it might be a hybrid of white-winged black tern and common tern, writing "''Sterna fissipes [''Chlidonias leucopterus''] et Hirundine [''Sterna hirundo''] natam''”.
This bird has a number of geographical races, differing mainly in size and minor plumage details.