Northern Flicker (Colaptes auratus) - HBW 7, p. 513

Taxonomy: Cuculus auratus Linnaeus, 1758, South Carolina.
Forms a superspecies with C. chrysoides; sometimes treated as conspecific but, although SW populations not significantly different genetically from that species, hybridization is very limited (in C & S Arizona), with moderate ecological separation too, and the two are better regarded as allospecies. Races commonly divided into four geographical groups, each considered a separate species in the past: “auratus group” (which includes luteus) in N & E North America, with yellow flight-feather shafts; “cafer group” (also including collaris, mexicanus, nanus and extinct rufipileus) in W North America and Mexico, with red shafts; “mexicanoides group” in highlands from S Mexico to Nicaragua; and geographically isolated “chrysocaulosus group” (with gundlachi) in Cuba and Grand Cayman. First two groups interbreed in extensive and long since stable hybrid zone from Alaska through the Great Plains, where relatively few individuals are typical of one form or the other, and non-assortative mating is common. Relationships among groups and individual races complex, poorly understood; also, considerable individual variation occurs, and races interbreed wherever they meet; further research and revision needed. Additional described races, considered to represent intergrades or otherwise inadequately differentiated, include borealis (NW to NC North America), sedentarius (Santa Cruz I, California), martirensis (San Pedro Mártir Mts, in NW Baja California) and pinicolus (highlands of El Salvador to N Nicaragua). Race rufipileus (Guadalupe I, off W Baja California) is extinct. Nine extant subspecies recognized.