Pilón Lajas Biosphere Reserve and Communal Lands (Pilón Lajas) ranges from 300 m to 1,400 m altitude in the departments of Beni and La Paz, Bolivia. It is located in the Bolivian and Peruvian lower yungas Endemic Bird Area (054) and within one of the regions of highest conservation priority in the Neotropics. Pilón Lajas includes primary evergreen tropical lowland forest, foothill forest, and lower montane forest. Vegetation heterogeneity forms the basis for the high species richness of the area. A population of approximately 600 Chiman, Moseten and Tacana indigenous people live within the reserve. Little has been published regarding the avifauna of Pilón Lajas. Here we present the results of visual observations and tape recordings of 22 ornithological surveys, recording 502 bird species. Serranía Pilón is the most intensively studied and species-rich mountain range with 332 species, 48 of which have been recorded only in this area within Pilón Lajas. We present 26 new departmental records and evidence of breeding for 42 species. The reserve protects three globally Vulnerable and three globally Near Threatened species, four species of High Conservation Priority and 32 of Medium Conservation Priority. Together with Madidi National Park and the adjacent Bahuaja Sonene National Park in south-eastern Peru, Pilón Lajas forms a unique protected area system of more than 3.5 million ha and plays an important role in the establishment of biological corridors along the eastern Andean slope in Bolivia.