Yellow warbler, Setophagia petechia. The Yellow Warbler is a very common and widespread warbler, breeding throughout North America and wintering in Central America. There are about 35 subspecies, each defined by breeding season, locality, and male breeding plumage. The genus Setophagia means “moth eater,” which makes sense as the vast majority of their diet is insects, especially caterpillars. The Yellow Warbler is an important species for maintaining insect populations, especially the ones that are in Costa Rican coffee plantations.