Terns are
seabirds in the
family Sternidae that have a worldwide distribution and are normally found near the
sea,
rivers, or
wetlands. Previously considered a subfamily of the
gulls, Laridae, they are now usually given full family status and divided into eleven
genera. They are slender, lightly built birds with long, forked tails, narrow wings, long bills, and relatively short legs. Most species are pale grey above and white below, with a contrasting black cap to the head, but the
marsh terns, the
Inca tern, and some
noddies have dark
plumage for at least part of the year. The sexes are identical in appearance, but young birds are readily distinguishable from adults. Terns have a non-breeding plumage, which usually involves a white forehead and much-reduced black cap.