The Collaborative International Dictionary of English v.0.48:

heathfowl \heathfowl\, heath fowl \heath fowl\n.
   A large Northern European black grouse (Lyrurus tetrix
   formerly Tetrao tetrix) with a lyre-shaped tail; it is also
   called heath grouse, black game, black grouse, heath
   poult, heath fowl, and moor fowl. See heath grouse
   under heath, above.

   Syn: European black grouse, Lyrurus tetrix.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

heathfowl
    n 1: large northern European grouse that is black with a lyre-
         shaped tail [syn: European black grouse, heathfowl,
         Lyrurus tetrix]