Systematics
Geographic Variation; Subspecies
Two subspecies have been named to describe morphological variation. As presently defined, boundary between these named forms runs from e. Texas northward approximately between 96 and 97°W (see Am. Ornithol. Union 1957, Paynter 1970), but may be farther east (Storer 1951, Robbins and Easterla 1992). P. c. ciris (Linnaeus, 1758) occurs east of this line; described as darker red in adult males and darker yellow-green in adult females, and with smaller mean wing length than that of P. c. pallidior Mearns, 1911, which occurs west of this boundary. P. c. pallidior characterized by "pinker and less orange hue" on red underparts of males (Storer 1951). Subspecies are only weakly differentiated (Storer 1951); differences in plumage and size show much overlap and are minor, clinal, and not distinctive; do not obviously justify nomenclatural distinctions (Thompson 1991b). Wing-chord shows largest change between 93 and 95°W longitude (Thompson 1992).
A further concern about the biological reality of these 2 subspecies is the fact that the boundary between them does not coincide with a 550-km gap at 85°W longitude that currently separates eastern and western breeding populations. Eastern and western populations differ in some dramatic ways. Western population migrates 2 mo earlier than eastern population to areas in s. Arizona and nw. Mexico to begin flight-feather molt and then continue to migrate farther to wintering areas in s. Texas, Mexico, and Central America. Eastern population completes flight-feather molt on breeding grounds along Atlantic Coast before migrat-ing to s. Florida, Bahamas, and Cuba (Thompson 1991a, 1991b).
Gene flow between these 2 populations of Painted Buntings (those east and west of 85°W) is likely more limited than gene flow between the 2 described subspecies as currently understood (Thompson 1991b). Genetic studies are warranted to examine the distinctness of these 2 populations, and to suggest, perhaps, that the subspecies be abandoned or redefined with new boundaries, or even that 2 species be recognized: Eastern Painted Bunting (P. ciris) and Western Painted Bunting (P. pallidior; Sibley and Monroe 1993).
