The Collaborative International Dictionary of English v.0.48:

Bluethroat \Blue"throat`\, n. (Zool.)
   A singing bird of northern Europe and Asia (Cyanecula
   Suecica), related to the nightingales; -- called also
   blue-throated robin and blue-throated warbler.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bluethroat
    n 1: songbird of northern Europe and Asia [syn: bluethroat,
         Erithacus svecicus]