The Greater Crested Tern, Crested Tern or Swift Tern, (Thalasseus bergii), is a seabird in the tern family which 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.