 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 . 
