yel·low·ham·mer 
(yĕlō-hăm′ər)
(yĕlō-hăm′ər)n.
1. A small bunting (Emberiza citrinella) native to Eurasia and northern Africa and introduced into New Zealand, having bright yellow plumage on the head, neck, and breast.
2. See yellow-shafted flicker.
[By folk etymology from earlier yelambre, perhaps from Middle English *yelwambre : yelow, yellow; see YELLOW + Old English amore, a kind of bird.]