Gull-billed Tern

Gull-billed Tern, Sterna nilotica, is a seabird of the tern family Sternidae.

It breeds in warmer parts of the world in southern Europe, temperate and eastern Asia, both coasts of North America, eastern South America and Australia. This bird has a number of geographical races, differing mainly in size and minor plumage details.

All forms show a post-breeding dispersal, but the northern breedesr are most migratory, wintering south to Africa, the Caribbean and northern South America, southern Asia and New Zealand.

This species breeds in colonies on lakes, marshes and coasts. It nests in a ground scrape and lays two to five eggs.

This is a somewhat atypical tern, in appearance like a Sterna tern, but with feeding habits more like the Childonias marsh terns, Black Tern and White-winged Black Tern. It is sometimes grouped in the genus Sterna, and sometimes given its own genus Gelochelidon.

Gull-billed Tern does not normally plunge dive for fish, like the other white terns, but feeds on insects taken in flight, and will also take frogs and small mammals.

This is a large and powerful tern, similar in size and general appearance to a Sandwich Tern, but the short thick gull-like bill, broad wings, long legs and robust body are distinctive. The summer adult has grey upperparts, white underparts, a black cap, strong black bill and black legs. The call is a characteristic ker-wik.

In winter, the cap is lost, and there is a dark patch through the eye like a Black-headed Gull. Juvenile Gull-billed Terns have a fainter mask, but otherwise look much like winter adults.

Juvenile Sandwich Terns have a short bill, and are frequently mistaken for Gull-billed Tern where the latter species is uncommon, such as North Sea coasts.