Three subspecies of Pale-billed Woodpecker currently are recognized (Short 1982, Winkler and Christie 2002), which differ slightly in size and in plumage color.
Nominate guatimalensis (Hartlaub 1844) - southern Mexico, from Veracruz and from eastern Oaxaca (east of the Isthmus of Tehuantepec), south to western Panama in western Bocas del Toro and western Chiriquí (Short 1982, Binford 1989, Ridgely and Gwynne 1989).
nelsoni (Ridgway 1911) - western Mexico, from Sonora south to Oaxaca (Miller et al. 1957, Binford 1989, Russell xxxx). Averages slightly smaller in size than guatimalensis. Also, the plumage is browner (less black), although the difference may be due in part to fading, from greater exposure to the sun in more xeric environments; the color of the underwing coverts and of the pale markings on the back is whiter (less buffy); and a tendency for barring (brown and black) on the lower back and rump (Short 1982). This barring on the upperparts is more prevalent in the northern part of the range, on which basis the population in Sonora and Sinaloa earlier was recognized as a separate subspecies, dorsofasciatus; but this barring is a character that appears, with varying levels of frequency, in all populations of the species.
regius Reichenbach 1854 - eastern Mexico, from Tamaulipas south to Veracruz. Averages larger than guatimalensis.