The Yellow Warbler (Setophaga petechia) comprises three groups of subspecies distributed across the Americas, from Alaska and northern Canada south through the West Indies and the mainland of Middle America to the northern coast of South America and the Galapagos Islands. The groups differ primarily in the head pattern of adult males (Lowther et al. 1999). The Northern Yellow Warbler (S. p. aestiva group) comprises the predominantly migratory subspecies with a green and/or yellow crown that breed across much of the United States, Canada, and northern and central Mexico; the Golden Yellow Warbler (S. p. petechia group) comprises the largely resident subspecies, most with a chestnut crown, found in south Florida, the Caribbean, and the coast of northeastern South America; and the Mangrove Yellow Warbler (S. p. erithachorides group) comprises the largely resident subspecies, most with a fully chestnut head, found in coastal mangroves from extreme southern Texas and central Baja California south as far as the coast of northwestern South America, with an isolated population on the Galapagos Islands that resembles the Golden Yellow Warbler in the extent of red on the head (Lowther et al. 1999). Although currently considered one species (AOU 1998), each of the three subspecies groups has been considered a full species by some authors (Hellmayr 1935).