The Collaborative International Dictionary of English v.0.48:

Sheldfowl \Sheld"fowl`\, n. (Zool.)
   The common sheldrake. [Prov. Eng.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sheldrake \Shel"drake`\, n. [Sheld + drake.]
   1. (Zool.) Any one of several species of large Old World
      ducks of the genus Tadorna and allied genera, especially
      the European and Asiatic species. (Tadorna cornuta syn.
      Tadorna tadorna), which somewhat resembles a goose in
      form and habit, but breeds in burrows.
      [1913 Webster]

   Note: It has the head and neck greenish black, the breast,
         sides, and forward part of the back brown, the
         shoulders and middle of belly black, the speculum
         green, and the bill and frontal bright red. Called also
         shelduck, shellduck, sheldfowl, skeelduck,
         bergander, burrow duck, and links goose.
         [1913 Webster]

   Note: The Australian sheldrake (Tadorna radja) has the
         head, neck, breast, flanks, and wing coverts white, the
         upper part of the back and a band on the breast deep
         chestnut, and the back and tail black. The chestnut
         sheldrake of Australia (Casarca tadornoides) is
         varied with black and chestnut, and has a dark green
         head and neck. The ruddy sheldrake, or Braminy duck
         (Casarca rutila), and the white-winged sheldrake
         (Casarca leucoptera), are related Asiatic species.
         [1913 Webster]

   2. Any one of the American mergansers.
      [1913 Webster]

   Note: The name is also loosely applied to other ducks, as the
         canvasback, and the shoveler.
         [1913 Webster]