Townsend's warbler (Setophaga townsendi) is a small songbird of the New World warbler family. These birds have a yellow face with a black stripe across their cheeks extending into an ear patch, a thin pointed bill, two white wing bars, olive upperparts with black streaks on their backs and flanks, and a white belly. Adult males have a black cap, black throat and yellow lower breast; females have a dark cap and a yellow throat. Immature birds are similar to females with a dark green cap and cheeks. Adults are 4.5- 5inches in length. The COSA lies in the Townsend's warbler's migration path, so can be spotted from April to May and in October