The Collaborative International Dictionary of English v.0.48:

Junco \Jun"co\, n. (Zool.)
   Any bird of the genus Junco, which includes several species
   of North American finches; -- called also snowbird, or
   blue snowbird.
   [1913 Webster]

WordNet (r) 3.0 (2006):

junco
    n 1: small North American finch seen chiefly in winter [syn:
         junco, snowbird]