The Caspian Tern
, Sterna caspia
, is found patchily distributed throughout the world. Despite the scattered distribution and its extensive range, it is monotypic, with no subspecies accepted. In the following photograph the bird with the red bill, stretching its wings, is the Caspian tern. The bird in the foreground is a swift tern.Large view
They feed mainly on fish, which they dive for, hovering high over the water and then plunging. Their diet is supplemented with aquatic invertebrates and occasionally large insects and the young and eggs of other birds. They may fly up to 60 km from the breeding colony to catch fish, often fishing on freshwater lakes as well as at sea. Caspian Terns will occasionally pirate food from other birds.
Breeding is in spring and summer, with one to three pale blue green eggs, heavily spotted brown, 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.
It is the world's largest tern 48–56 cm long, with a wingspan of 127–140 cm and a weight of 574–782g.