From The Collaborative International Dictionary of English v.0.48 [gcide]:
Capercailzie \Ca"per*cail`zie\, or Capercally \Ca"per*cal`ly\,
n. [Gael, capulcoile.] (Zool.)
A species of black Old World grouse (Tetrao uragallus) of
large size and fine flavor, found in northern Europe and
formerly in Scotland; -- called also cock of the woods and
horse of the wood. [Written also capercaillie,
capercaili.]
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
capercailzie
n 1: large black Old World grouse [syn: capercaillie,
capercailzie, horse of the wood, Tetrao urogallus]