A Black-naped Tern in flight over the Gulf of Thailand, off Koh Si Chang, a small island in Chonburi Province. It has a forked tail, that is best visible during flight.

They are mostly white, with a pale greyish-white belly, silvery greyish back and wings, and a black triangular nape, that contrasts with the white crown, face and breast, and of which the top corners stretch forward, forming black eye-stripes that reach to just over the eyes, without affecting the lores, which are also white.

The beak and legs are blackish, and though hardly noticeable, the outermost tip of the bill is actually pale yellowish.