For most of the 20th century, the Red-naped Sapsucker (Sphyrapicus nuchalis), the Yellow-bellied Sapsucker (S. varius), and the Red-breasted Sapsucker (S. ruber) were treated as belonging to a single species, S. varius (sometimes the Red-breasted Sapsucker was excluded). The three species are very similar, including genetically, and Red-naped Sapsuckers hybridize extensively with Red-breasted Sapsuckers (and, to a lesser extent, with Yellow-bellied Sapsuckers), but data on mating preferences has supported their status as biological species (Johnson and Johnson 1985; Cicero and Johnson 1995).
The Red-naped Sapsucker, which breeds across much of the western third of the United States and adjacent Canada, looks very similar to the eastern Yellow-bellied Sapsucker, but has a variable red patch on the back of the head, more extensive red on the male's throat, and red on the female's throat (absent from Yellow-bellied Sapsucker female's throat).
Red-naped Sapsuckes are common in summer in deciduous and mixed forests, especially around aspens, in the Great Basin and Rocky Mountain ranges, with a small number in the Sierra Nevada. They are rare west of the Sierra Nevada and very rare in the Pacific Northwest and west of the Cascades (where Red-breasted Sapsuckers are common). They occur casually east to the western Great Plains. They winter from southern California, southern Nevada, and central Arizona and New Mexico south to central Mexico.
(Howell 1952; Kaufman 1996: Dunn and Alderfer 2011)