Hybrid Zones and the Northern Flicker (Colaptes auratus):

Once treated as separate species, the eastern Yellow-shafted Flicker and western Red-shafted Flicker are now considered to be subspecies of Northern Flciker. In addition to the differences in their wing and tail feathers, males differ in the color of their mustache stripes. Where these forms meet in North America (shown in purple on the range map below) they interbreed freely, producing a continuum of variation in wing and mustache colors. An unusual feature of the hybrid zone is that it is narrow in the southern Great Plains and wide in the northern prairies. the width of the ecotone connecting the ranges of these two flickers closely matches the width of their hybrid zone. This is one of only a few avian hybrid zones where hybrids may be superior competitors relative to both of their parental groups in this zone of ecological transition.

Northern Flicker range map, redrawn from W.S. Moore and J.T. Price, 1993

Northern Flickers occur in two color forms: the "Red-shafted" in the West and the "Yellow-shafted" east of the Rocky Mountains. The Gilded Flicker, found in the Sonoran Desert of the Southwest, has recently been split off as its own species. The ice ages separated the ancestral flickers, keeping them scattered in several refugia for thousands of years. Today those barriers are gone. The Gilded has become adapted to the desert, whereas the two northern populations inhabit the same type of woodland habitat, with only the treeless Great Plains keeping them somewhat apart. All three forms interbreed where their ranges come together, and numerous confusing intermediates can be found. In the East, flickers are the only brown-backed woodpeckers, and the only woodpeckers in North America that commonly feed on the ground, searching for ants and beetle larvae.

Red-shafted Northern Flickers. Female (left) and male (right).

Male Yellow-shafted Norther Flicker (Colapted auratus)
Female interrade or hybrid Norther Flicker, note the mix of Red-shafted and Yellow-shafted traits.

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