The Collaborative International Dictionary of English v.0.48:

Whitethroat \White"throat`\, n. (Zool.)
   Any one of several species of Old World warblers, esp. the
   common European species (Sylvia cinerea), called also
   strawsmear, nettlebird, muff, and whitecap, the
   garden whitethroat, or golden warbler (Sylvia
   hortensis), and the lesser whitethroat (Sylvia curruca).
   [1913 Webster]

WordNet (r) 3.0 (2006):

whitethroat
    n 1: Old World warbler similar to the greater whitethroat but
         smaller [syn: lesser whitethroat, whitethroat, Sylvia
         curruca]
    2: greyish-brown Old World warbler with a white throat and
       underparts [syn: greater whitethroat, whitethroat,
       Sylvia communis]
    3: common North American finch with a white patch on the throat
       and black-and-white striped crown [syn: white-throated
       sparrow, whitethroat, Zonotrichia albicollis]