The avifauna of Viruá National Park, Roraima, reveals megadiversity in Northern Amazonia

Abstract

While many published maps of avian species richness indicate northern Amazonia to be somewhat species-poor, recent surveys reveal that this area actually possesses one of the most species-rich avifaunas in the Neotropical lowlands. Our surveys indicate that at least 520 bird species occur in Viruá National Park (VNP) and adjacent areas, which is located in the Brazilian state of Roraima (northern Amazonia). Here, we present the results of our ornithological efforts since 2001, based on audio-visual and mistnetting surveys, vouchered by tape and digital recordings, photographs, and collected specimens. VNP is dominated by Amazonian white-sand forest (locally known as campina and campinarana) on an extensive floodplain influenced by muddy-, clear-, and blackwater rivers, forming a complex mosaic of habitats that includes várzea, igapó, and hilltop "islands" with terra-firme forest. The high avian diversity found at VNP is likely due to both biogeographic and local-scale processes. Each habitat contains a particular avian assemblage. Patches of terra-firme forest have a typical Guianan avifauna. Campina and campinarana contain unique species, including some poorly known and range-restricted (e.g., Aprositornis disjuncta), as well as species typical of the northern Roraiman savannas (e.g., Icterus nigrogularis). The várzea of the Rio Branco (with its associated river islands) is particularly species-rich, including the endemic Cercomacra carbonaria and isolated populations of white-river-island specialists (e.g., Mazaria propinqua). VNP protects important ecological ecotones and biogeographical contact zones, as well as 27 threatened and 45 migratory bird species. On the other hand, 71 species reported for our study area have been found outside the current boundaries of the park. Ongoing proposals of expanding the limits of the park would absorb most of these species. With its outstanding bird species richness and wide variety of habitats, VNP emerges as an important site for Amazonian avian research, tourism, and conservation. Despite the park's protected status, the Brazilian government plans to build a hydroelectric dam in the region, representing the main threat to its avifauna and overall biodiversity.