Divergence in plumage, voice, and morphology indicates speciation in Rufous-capped Warblers (Basileuterus rufifrons)

The biodiversity of the Neotropics is considerable, but it is likely underestimated owing to gaps in sampling effort and a focus on using morphological features of animals to determine species differences rather than divergence in their mating signals and behavior. Recent multi-trait analyses incorporating morphological, plumage, and vocal data have allowed for more accurate quantification of tropical biodiversity. We present a comprehensive study of morphological features, plumage, and vocalizations of the Neotropical resident Rufous-capped Warbler (Basileuterus rufifrons). This species’ taxonomic status is controversial because the B. r. salvini subspecies is intermediate in plumage coloration between the neighboring B. r. delattrii and B. r. rufifrons subspecies. Using morphological and spectral plumage measurements of field and museum specimens, as well as analyses of vocalizations from field recordings and sound libraries, we compared phenotypes of all eight currently recognized Ru...