We combined findings of an avian field survey conducted in 2003 with the efforts of other observers to develop a comprehensive species list for the Katavi-Rukwa ecosystem; a biologically rich area of western Tanzania. Our 2003 survey, during the dry season, yielded 222 species of birds, four of which had not been reported previously. In combination with other publications, field reports, and incidental observations we documented 458 species of birds occurring in this ecosystem. The confirmed presence of ten globally threatened species, 18 biome restricted species, one range restricted species (Tanzanian masked weaver Ploceus reichardi), and significant numbers of African skimmer (Rynchops flavirostris), a colonial waterbird, strongly reinforces the classification of the Katavi National Park as an Important Bird Area in Tanzania. A synopsis of species found in this area supports the view that the avifauna of the Katavi-Rukwa ecosystem is biogeographically affiliated with the Zambezian biome. These findings will provide a baseline for conservation, management, and future biodiversity and avian research efforts in the Katavi-Rukwa ecosystem.