The Collaborative International Dictionary of English v.0.48:

Catbird \Cat"bird\, n. (Zool.)
   An American bird (Galeoscoptes Carolinensis), allied to the
   mocking bird, and like it capable of imitating the notes of
   other birds, but less perfectly. Its note resembles at times
   the mewing of a cat.
   [1913 Webster]

WordNet (r) 3.0 (2006):

catbird
    n 1: any of various birds of the Australian region whose males
         build ornamented structures resembling bowers in order to
         attract females [syn: bowerbird, catbird]
    2: North American songbird whose call resembles a cat's mewing
       [syn: catbird, grey catbird, gray catbird, Dumetella
       carolinensis]