cowbird

詳細解釋：

cow.bird

n.（名詞）
Any of various blackbirds of the genusMolothrus, especially the common North American species M. ater, that lay their eggs in the nests of other birds and are often seen accompanying herds of grazing cattle.
牛鸝：任一種牛鸝屬 .的黑色鳥類，尤指北美洲常見的 褐頭牛鸝 ，在其他鳥類的巢中下蛋，並經常可以看到它們和草場上的牛群在一起

來源：
[From their habit of staying with cattle]
[由於它們跟隨牛群的習性而得名]