Source : Webster's Revised Unabridged Dictionary (1913)

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.] (Zo["o]l.)
   (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.]

Source : WordNet®

Emberiza citrinella
     n : European bunting the male being bright yellow [syn: {yellowhammer},
          {yellow bunting}]