Chionis

The sheathbills are a family of birds, Chionidae. Classified in the wader order Charadriiformes, the family consists of one genus, Chionis with two species. They breed on subantarctic islands and the Antarctic Peninsula, and the snowy sheathbill migrates to the Falkland Islands and coastal southern South America in the southern winter; they are the only bird family endemic as breeders to the Antarctic region. They are also the only Antarctic birds without webbed feet. Taxonomy The genus Chionis was introduced in 1788 by the German naturalist Johann Reinhold Forster. The type species is the snowy sheathbill. The genus name is from the Ancient Greek meaning snow. Description They have white plumage including a thick layer of down, with only the face and leg colours distinguishing the two species. They look plump and dove-like, but are believed to be similar to the ancestors of the modern gulls and terns. There is a rudimentary spur on the "wrist" (carpal) joint, as in plovers. The skin around the eye is bare, as is the skin above the bill, which has carbuncular swellings. They derive their English name from the horny sheath which partially covers the upper mandible of their stout bills. They are commonly known in the Antarctic as "Mutts" because of their call which is a soft "Mutt, mutt, mutt" Behaviour Sheathbills habitually walk on the ground, somewhat like rails. They fly only when alarmed or in migration, looking like pigeons.