The Collaborative International Dictionary of English v.0.48:

Whistler \Whis"tler\, n. [AS. hwistlere.]
   [1913 Webster]
   1. One who, or that which, whistles, or produces or a
      whistling sound.
      [1913 Webster]

   2. (Zool.)
      (a) The ring ousel.
      (b) The widgeon. [Prov. Eng.]
      (c) The golden-eye.
      (d) The golden plover and the gray plover.
          [1913 Webster]

   3. (Zool.) The hoary, or northern, marmot (Arctomys
      pruinosus).
      [1913 Webster]

   4. (Zool.) The whistlefish.
      [1913 Webster]