Tern-202 Postcard

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. Their flight is buoyant and graceful. 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. The terns are birds of open habitats that typically breed in noisy colonies and lay their eggs on bare ground with little or no nest material. However, the marsh terns construct floating nests from the vegetation in their wetland habitats, and a few species build simple nests in trees, on cliffs or in crevices. The white tern, uniquely, lays its single egg on a bare tree branch. Depending on the species, 1–3 eggs make up the clutch. Most species feed on fish caught by diving from flight, but the marsh terns are insect-eaters, and some large terns will supplement their diet with small land vertebrates. Many terns are long-distance migrants, and the Arctic tern may see more daylight in a year than any other animal.