The Collaborative International Dictionary of English v.0.48:

bustard \bus"tard\ (b[u^]s"t[~e]rd), n. [OF. & Prov. F.
   bistarde, F. outarde, from L. avis tarda, lit., slow bird.
   --Plin. 10, 22; "proxim[ae] iis sunt, quas Hispania aves
   tardas appellat, Gr[ae]cia 'wti`das."] (Zool.)
   A bird of the genus Otis.
   [1913 Webster]

   Note: The great or bearded bustard (Otis tarda) is the
         largest game bird in Europe. It inhabits the temperate
         regions of Europe and Asia, and was formerly common in
         Great Britain. The little bustard (Otis tetrax)
         inhabits eastern Europe and Morocco. Many other species
         are known in Asia and Africa.
         [1913 Webster]

WordNet (r) 3.0 (2006):

Otis tarda
    n 1: largest European land bird [syn: great bustard, Otis
         tarda]