Narrow-billed Woodcreeper (Lepidocolaptes angustirostris) - HBW 8, p. 439

Taxonomy: Dendrocopus angustirostris Vieillot, 1818, Paraguay.
Unclear whether basal to or within radiation of genus; proposed placement as sister to L. leucogaster, however, seems biogeographically unlikely. Races form two groups, apparently intergrading across broad zone of contact extending from E Bolivia to SE Brazil: members of “angustirostris group” (which also includes hellmayri, certhiolus and praedatus) are browner above and more heavily streaked below, but those of “bivittatus group” (with griseiceps, coronatus and bahiae) are more rufescent above and largely unstreaked below. Proposed races dabbenei (SW Paraguay, N Argentina) and chacoensis (NE Argentina) synonymized with praedatus, which also intergrades widely with nominate; described race immaculatus (N Bolivia) synonymized with bivittatus. Description of griseiceps possibly based on individual variant with extremely pale plumage; known only from type locality, but description matched in all respects by birds in a series from N Amazonian Brazil (Amapá). Assessment of geographical variation in plumage complicated by marked individual, age-related and seasonal (wear) differences. Eight subspecies recognized.