Greater crested tern

The greater crested tern (Thalasseus bergii), also called crested tern or swift tern, is a seabird in the tern family that nests in dense colonies on coastlines and islands in the tropical and subtropical Old World. Its five subspecies breed in the area from South Africa around the Indian Ocean to the central Pacific and Australia, all populations dispersing widely from the breeding range after nesting. This large tern is closely related to the royal and lesser crested terns, but can be distinguished by its size and bill colour.

The greater crested tern has grey upperparts, white underparts, a yellow bill, and a shaggy black crest that recedes in winter. Its young have a distinctive appearance, with strongly patterned grey, brown and white plumage, and rely on their parents for food for several months after they have fledged. Like all members of the genus Thalasseus, the greater crested tern feeds by plunge diving for fish, usually in marine environments; the male offers fish to the female as part of the courtship ritual.

Thalasseus

Thalasseus, the crested terns, is a genus of six species of seabirds in the tern family. Thalasseus signifies a "creature of the sea". It has a worldwide distribution, and many of its species are abundant and well-known birds in their ranges. This genus had originally been created by Friedrich Boie in 1822, but had been abandoned until a 2005 study confirmed the need for a separate genus for the crested terns.

These large terns breed in very dense colonies on coasts and islands, and exceptionally inland on suitable large freshwater lakes close to the coast. They nest in a ground scrape.

Thalasseus terns feed by plunge-diving for fish, almost invariably from the sea. They usually dive directly, and not from the "stepped-hover" favoured by, for example, the Arctic tern. The offering of fish by the male to the female is part of the courtship display.

These species have long thin sharp bills, usually a shade of yellow or orange except in the Sandwich tern where the bill is black with a yellow tip in most subspecies. All species have a shaggy crest. In winter, the Thalasseus terns' foreheads become white.