Source : Webster's Revised Unabridged Dictionary (1913)

Yellowbird \Yel"low*bird`\, n. (Zo["o]l.)
   (a) The American goldfinch, or thistle bird. See {Goldfinch}.
   (b) The common yellow warbler; -- called also {summer
       yellowbird}. See Illust. of {Yellow warbler}, under
       {Yellow}, a.

Source : WordNet®

yellowbird
     n 1: yellow-throated American wood warbler [syn: {yellow warbler},
           {golden warbler}, {Dendroica petechia}]
     2: American finch whose male has yellow body plumage in summer
        [syn: {New world goldfinch}, {goldfinch}, {Spinus tristis}]