GEOGRAPHIC-VARIATION IN COLORATION AND MORPHOLOGY OF THE ACORN WOODPECKER

Abstract

Although geographic variation in coloration and morphology of Acorn Woodpeckers (Melanerpes formicivorus) is thought to be slight, a sedentary species restricted to a particular habitat across a broad geographic range may be expected to exhibit some geographic differentiation. I analyzed seven morphometric and five plumage coloration characters on 1,531 study skins from across the species' geographic range. Dividing the specimens examined into 25 population samples, I found highly significant geographic differences in most of the characters analyzed, including clinal patterns and discrete differences in both morphometric and plumage characters. Patterns of geographic differentiation in the two character sets were not significantly concordant. It is possible to identify seven geographic units within the species, each of which is diagnosable based on combinations of discrete and continuous character states.