Tern sea terns have light grey or white body plumage as adults, with a black cap to the head. The legs and bill are various combinations of red, orange, yellow, or black depending on species. The pale plumage is conspicuous from a distance at sea, and may attract other birds to a good feeding area for these fish-eating species. When seen against the sky, the white underparts also help to hide the hunting bird from its intended prey. The Inca tern has mainly dark plumage, and three species that mainly eat insects, the black tern, white-winged tern, and black-bellied tern, have
Royal tern adult royal tern has an average wingspan of , for both sexes, but their wingspan can range from . The royal tern's length ranges from and their average weight is anywhere from . The calls of the royal tern are usually short, clear shrills. Some of the shrills sound like "kree" or "tsirr"; the royal tern also has a more plover like whistle that is longer, rolling and is more melodious. In various parts of its range, the royal tern could be confused with the elegant tern, lesser crested tern (the other orange-billed terns), and the greater crested tern. It