Geographic distribution and morphological variation in Pteroglossus beauharnaesii (Ramphastidae) in southern Amazonia

The Curl-crested Aracari (Pteroglossus beauharnaesii) is one of the most remarkable Neotropical species, possessing a colorful body plumage and distinctive curly, shiny black crown feathers. It is a southern Amazonian species, occurring from Peru east to central Brazilian Amazonia, and in spite of its wide distribution and remarkable appearace, few studies have dealt with its morphological variation. It presents a noticeable plumage variation across its distribution regarding the presence/absence of black spots on throat and cheeks. In order to conduct a taxonomic revision of the species, we analyzed 159 skin specimens housed in seven Brazilian and North American museums. We evaluated plumage coloration and took measurements of bill, wing, tail and tarsus. Also, we estimated the number of black spots in a 2x2cm square randomly positioned in the throat and cheeks. Principal Components Analysis of the morphometric measurements and the plumage coloration analyses showed no significant or consistent differences between different populations. Nonetheless, the plumage analysis showed a consistent, notable difference between populations separated by the Rio Madeira. These results demonstrate that specimens from west of that river show distinct black spots in throat and cheeks – which are more pronounced on specimens from the extreme western distribution – while the specimens east of the river are diagnosable by the complete lack of those spots, indicating the existence of two diagnosable taxa. A molecular study of these populations is in progress, including samples from the possible contact zone between populations in the upper Madeira River.