The Collaborative International Dictionary of English v.0.48:

Birdcall \Bird"call`\, n.
   1. A sound made in imitation of the note or cry of a bird for
      the purpose of decoying the bird or its mate.
      [1913 Webster]

   2. An instrument of any kind, as a whistle, used in making
      the sound of a birdcall.
      [1913 Webster]

WordNet (r) 3.0 (2006):

birdcall
    n 1: the characteristic sound produced by a bird; "a bird will
         not learn its song unless it hears it at an early age"
         [syn: birdcall, call, birdsong, song]
    2: a device for imitating a birdcall