The Collaborative International Dictionary of English v.0.48:

Riflebird \Ri"fle*bird`\, n. (Zool.)
   Any one of several species of beautiful birds of Australia
   and New Guinea, of the genera Ptiloris and Craspidophora,
   allied to the paradise birds.
   [1913 Webster]

   Note: The largest and best known species is Ptiloris
         paradisea of Australia. Its general color is rich
         velvety brown, glossed with lilac; the under parts are
         varied with rich olive green, and the head, throat, and
         two middle tail feathers are brilliant metallic green.
         [1913 Webster]

WordNet (r) 3.0 (2006):

riflebird
    n 1: velvety black Australian bird of paradise with green and
         purple iridescence on head and tail [syn: riflebird,
         Ptloris paradisea]