The Collaborative International Dictionary of English v.0.48:

Bluebird \Blue"bird`\, n. (Zool.)
   A small song bird (Sialia sialis), very common in the
   United States, and, in the north, one of the earliest to
   arrive in spring. The male is blue, with the breast reddish.
   It is related to the European robin.
   [1913 Webster]

   Pairy bluebird (Zool.), a brilliant Indian or East Indian
      bird of the genus Irena, of several species.
      [1913 Webster]

WordNet (r) 3.0 (2006):

bluebird
    n 1: fruit-eating mostly brilliant blue songbird of the East
         Indies [syn: fairy bluebird, bluebird]
    2: blue North American songbird