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
Sandwich tern and its underparts white, and this tern looks very pale in flight, although the primary flight feathers darken during the summer. The lesser crested tern and elegant tern differ in having all-orange bills; lesser crested also differs in having a grey rump and marginally stouter bill, and elegant in having a slightly longer, slenderer bill. Chinese crested tern is the most similar to Sandwich, but has a reversal of the bill colour, yellow with a black tip; it does not overlap in range with Sandwich tern so confusion is unlikely. In winter, the adult Sandwich tern's forehead becomes white. Juvenile