UKBirds

Gull-Billed Tern

Gelochelidon nilotica

The Gull-billed Tern, formerly Sterna nilotica (Bridge et al., 2005), is a seabird of the tern family Sternidae. It is now considered to be in its own genus.

This is a fairly 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. It is 33-42 cm (13-17 in) in length and 76-91 cm (30-36 in) in wingspan. Body mass ranges from 150-292 g (5.3-10.3 oz).

In winter, the cap is lost, and there is a dark patch through the eye like a Forster's Tern or a Mediterranean 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.

It breeds in warmer parts of the world in southern Europe (and a very small isolated population in northern Germany and Denmark), 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 breeders are most migratory, wintering south to Africa, the Caribbean and northern South America, southern Asia and New Zealand.

The Gull-billed Tern is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.