Straight-billed Woodcreeper (Xiphorhynchus picus) - HBW 8, p. 435

Taxonomy: Oriolus Picus J. F. Gmelin, 1788, in Gujanae = “Cayenne”.
Formerly placed along with X. kienerii in a separate genus, Dendroplex, based on morphological differences, but both later merged with Xiphorhynchus because of problems with identification of sketch designated as type of Dendroplex; morphological distinction of Dendroplex supported by recent analysis of molecular data, which suggested that these species are distantly related to present congeners, and closer to Lepidocolaptes and Campylorhamphus. Holotype of Dendrornis [= Xiphorhynchus] Kienerii, subsequently recognized as a subspecies of X. picus by most authors, recently found to match more recently described “Dendroplex necopinus”, which is supported as specifically distinct from X. picus by vocal, ecological and molecular data. Assessment of geographic variation is complicated by marked individual variation, at least in some populations. Races fall into two groups, “picirostris group” (also including choicus, extimus, dugandi, paraguanae, longirostris, phalara) in Panama and N & NW South America, with remaining races constituting “picus group” of Amazonia and E South America; these groups treated as separate species by some authors, but not by others because of apparent hybrids from lower R Orinoco region of Venezuela; further work needed. Races similar within each group. Purported races bahiae (NE Brazil) and rufescens (NC Brazil) described on basis of average differences from nominate, but individual variation so marked that neither is considered diagnosable. Described race borreroi from S Colombia (E base of Andes in Caquetá) apparently not distinguishable from peruvianus, which itself is possibly indistinguishable from saturatior. Race choicus poorly differentiated from picirostris. Thirteen subspecies recognized.