The Royal tern is second in size after the Caspian Tern (the world's largest tern).
Royal Terns breed on the Atlantic and Pacific coasts of the southern United States, Mexico and the Caribbean. The slightly smaller subspecies Thalasseus maximus albididorsalis breeds in coastal west Africa. American birds winter south to Peru and Argentina, and African breeders move both north and south from the breeding colonies. African birds may reach as far north as Spain.
Royal Terns have a long yellow bill, pale grey upperparts, white underparts, and black legs. In winter, the black cap becomes patchy.