WordNet (r) 3.0 (2006):

songbird
    n 1: any bird having a musical call [syn: songbird,
         songster]

Moby Thesaurus II by Grady Ward, 1.0:

112 Moby Thesaurus words for "songbird":
   Heldentenor, Meistersinger, Philomel, alto, aria singer, avifauna,
   baby bird, baritenor, baritone, bass, basso, basso buffo,
   basso cantante, basso profundo, bird, bird of Jove, bird of Juno,
   bird of Minerva, bird of night, bird of passage, bird of prey,
   birdie, birdlife, birdy, blues singer, bulbul, cage bird, canary,
   cantatrice, cantor, caroler, chanter, chantress, chick,
   coloratura soprano, comic bass, contralto, countertenor, crooner,
   cuckoo, cygnet, deep bass, diva, diving bird, dove,
   dramatic soprano, eagle, eaglet, feathered songster,
   fish-eating bird, fledgling, flightless bird, fowl,
   fruit-eating bird, fulmar, game bird, heroic tenor, hymner,
   improvisator, insect-eating bird, lark, lead singer, lieder singer,
   mavis, melodist, mezzo-soprano, migrant, migratory bird,
   mockingbird, nestling, nightingale, opera singer, oriole,
   oscine bird, owl, passerine bird, peacock, peafowl, peahen,
   perching bird, pigeon, prima donna, psalm singer, ratite, ringdove,
   rock-and-roll singer, sea bird, seed-eating bird, shore bird,
   singer, singing bird, singstress, song sparrow, songster,
   songstress, soprano, squab, storm petrel, stormy petrel, swan,
   tenor, thrush, torch singer, vocalist, vocalizer, voice,
   wading bird, warbler, water bird, waterfowl, wildfowl, yodeler