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
Forster's tern its bill is red, tipped with black. In winter, the forehead becomes white and a characteristic black eye mask remains. Juvenile Forster's terns are similar to the winter adult. The call is a harsh noise like a black-headed gull. This species is unlikely to be confused with the common tern in winter because of the black eye mask, but is much more similar in breeding plumage. Forster's has a grey centre to its white tail, and the upperwings are pure white, without the darker primary wedge of the common tern. Forster's tern is a medium-sized tern with a slender body,