The Collaborative International Dictionary of English v.0.48:

Songster \Song"ster\ (s[o^]ng"st[~e]r), n. [AS. sangestre a
   female singer.]
   1. One who sings; one skilled in singing; -- not often
      applied to human beings.
      [1913 Webster]

   2. (Zool.) A singing bird.
      [1913 Webster]

WordNet (r) 3.0 (2006):

songster
    n 1: a composer of words or music for popular songs [syn:
         songwriter, songster, ballad maker]
    2: a person who sings
    3: any bird having a musical call [syn: songbird, songster]