The Collaborative International Dictionary of English v.0.48:

Sandpiper \Sand"pi`per\, n.
   1. (Zool.) Any one of numerous species of small limicoline
      game birds belonging to Tringa, Actodromas,
      Ereunetes, and various allied genera of the family
      Tringidae.
      [1913 Webster]

   Note: The most important North American species are the
         pectoral sandpiper (Tringa maculata), called also
         brownback, grass snipe, and jacksnipe; the
         red-backed, or black-breasted, sandpiper, or dunlin
         (Tringa alpina); the purple sandpiper (Tringa
         maritima: the red-breasted sandpiper, or knot (Tringa
         canutus); the semipalmated sandpiper (Ereunetes
         pusillus); the spotted sandpiper, or teeter-tail
         (Actitis macularia); the buff-breasted sandpiper
         (Tryngites subruficollis), and the Bartramian
         sandpiper, or upland plover. See under Upland. Among
         the European species are the dunlin, the knot, the
         ruff, the sanderling, and the common sandpiper
         (Actitis hypoleucus syn. Tringoides hypoleucus),
         called also fiddler, peeper, pleeps, weet-weet,
         and summer snipe. Some of the small plovers and
         tattlers are also called sandpipers.
         [1913 Webster]

   2. (Zool.) A small lamprey eel; the pride.
      [1913 Webster]

   Curlew sandpiper. See under Curlew.

   Stilt sandpiper. See under Stilt.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Fiddler \Fid"dler\, n. [AS. fi[eth]elere.]
   1. One who plays on a fiddle or violin.
      [1913 Webster]

   2. (Zool.) A burrowing crab of the genus Gelasimus, of many
      species. The male has one claw very much enlarged, and
      often holds it in a position similar to that in which a
      musician holds a fiddle, hence the name; -- called also
      fiddler crab, calling crab, soldier crab, and
      fighting crab.
      [1913 Webster]

   3. (Zool.) The common European sandpiper (Tringoides
      hypoleucus); -- so called because it continually
      oscillates its body.
      [1913 Webster]

   Fiddler crab. (Zool.) See Fiddler, n., 2.
      [1913 Webster]

WordNet (r) 3.0 (2006):

fiddler
    n 1: a musician who plays the violin [syn: violinist,
         fiddler]
    2: someone who manipulates in a nervous or unconscious manner
       [syn: twiddler, fiddler]
    3: an unskilled person who tries to fix or mend [syn:
       tinkerer, fiddler]