栖息于南极的海鸟
Sheathbill \Sheath"bill`\, n. (Zo["o]l.) Either one of two species of birds composing the genus {Chionis}, and family {Chionid[ae]}, native of the islands of the Antarctic seas. Note: They are related to the gulls and the plovers, but more nearly to the latter. The base of the bill is covered with a saddle-shaped horny sheath, and the toes are only slightly webbed. The plumage of both species is white.