[5] They have white plumage including a thick layer of down, with only the face and leg colours distinguishing the two species.

They derive their English name from the horny sheath which partially covers the upper mandible of their stout bills.

[7] The nests are lined messily with seaweed, stones, feathers, guano, bones, and occasionally plastic trash; even dead chicks may not be removed.

[2] Genetic studies of the order Charadriiformes show the sheathbills to be a sister group of the thick-knees of the family Burhinidae.

[8] Recent research on the Magellanic plover (Pluvianellus socialis) of southern South America has indicated it too may be classified within the sheathbill family.