The Caspian Tern ( Sterna caspia ) is a species of tern, with a subcosmopolitan but scattered distribution. Their breeding habitat is large lakes and ocean coasts in North America, and locally in Europe, Asia, Africa, and Australasia (Australia and New Zealand). North American birds migrate to southern coasts, the West Indies and northernmost South America. European and Asian birds spend the non-breeding season in the Old World tropics. African and Australasian birds are resident or disperse over short distances.
The global population is about 50,000 pairs; numbers in most regions are stable, but the Baltic Sea population (1,400–1,475 pairs in the early 1990s) is declining and of conservation concern.
The Caspian Tern is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.Breeding is in spring and summer, with one to three pale blue green eggs, with heavy brown spotting, being laid. They nest either together in colonies, or singly in mixed colonies of other tern and gull species. The nest is on the ground among gravel and sand, or sometimes on vegetation; incubation lasts for 26–28 days. The chicks are variable in plumage pattern, from pale creamy to darker grey-brown; this variation assists adults in recognizing their own chicks when returning to the colony from feeding trips. Fledging occurs after 35–45 days.