The Collaborative International Dictionary of English v.0.48:

Flicker \Flick"er\, n.
   1. The act of wavering or of fluttering; fluctuation; sudden
      and brief increase of brightness; as, the last flicker of
      the dying flame.
      [1913 Webster]

   2. (Zool.) The golden-winged woodpecker (Colaptes aurutus);
      -- so called from its spring note. Called also
      yellow-hammer, high-holder, pigeon woodpecker, and
      yucca.
      [1913 Webster]

            The cackle of the flicker among the oaks.
                                                  --Thoureau.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Yellowhammer \Yel"low*ham`mer\, n. [For yellow-ammer, where
   ammer is fr. AS. amore a kind of bird; akin to G. ammer a
   yellow-hammer, OHG. amero.] (Zool.)
      (a) A common European finch (Emberiza citrinella). The
          color of the male is bright yellow on the breast,
          neck, and sides of the head, with the back yellow and
          brown, and the top of the head and the tail quills
          blackish. Called also yellow bunting, scribbling
          lark, and writing lark. [Written also
          yellow-ammer.]
      (b) The flicker. [Local, U. S.]
          [1913 Webster]

WordNet (r) 3.0 (2006):

yellowhammer
    n 1: large flicker of eastern North America with a red neck and
         yellow undersurface to wings and tail [syn: yellow-shafted
         flicker, Colaptes auratus, yellowhammer]
    2: European bunting the male being bright yellow [syn:
       yellowhammer, yellow bunting, Emberiza citrinella]