Cocoa Woodcreeper (Xiphorhynchus susurrans) - HBW 8, p. 430

Taxonomy: Dendrocolaptes susurrans Jardine, 1847, Tobago.
Sister to X. guttatus and treated by most authors as conspecific, but recently elevated to full species on grounds of differences in calls and body size; geographical patterns in songs, however, more complex than previously realized, and size differences do not correspond to species limits as presently recognized. No published data support recognition by most recent authors of “nanus group” with X. susurrans instead of X. guttatus. Two subspecies groups, differing markedly in plumage patterns: “susurrans group” (with jardinei and margaritae) in E of range (Trinidad, Tobago, Margarita I and adjacent Venezuelan mainland), and “nanus group” (including all remaining races) in Central America, N Colombia and N & W Venezuela. Preliminary molecular analyses suggest close affinity of “nanus group” to nominate X. guttatus and allied race polystictus, but populations in “susurrans group” were not included in the analyses. Birds from NE Colombia and adjacent NW Venezuela, described as race demonstratus, considered inseparable from nanus. Eight subspecies recognized.