The Collaborative International Dictionary of English v.0.48:

Chatterer \Chat"ter*er\, n.
   1. A prater; an idle talker.
      [1913 Webster]

   2. (Zool.) A bird of the family Ampelid[ae] -- so called
      from its monotonous note. The Bohemion chatterer
      (Ampelis garrulus) inhabits the arctic regions of both
      continents. In America the cedar bird is a more common
      species. See Bohemian chatterer, and Cedar bird.
      [1913 Webster]

WordNet (r) 3.0 (2006):

chatterer
    n 1: an obnoxious and foolish and loquacious talker [syn:
         chatterer, babbler, prater, chatterbox, magpie,
         spouter]
    2: passerine bird of New World tropics [syn: cotinga,
       chatterer]