The Reserva Biológica do Mato Grande encompasses 5,161 hectares of wetlands, restinga forests and grasslands in southern Brazil. Aiming to assemble a list of bird species occurring in the reserve, we carried out 21 monthly expeditions from July 2007 to March 2009 and an additional visit on October 2014, totaling 341 hours of sampling. We additionally searched for records in online databases and museums. In total, 211 species of birds were found, compared to 223.83 (SD = 3.88) and 214.68 (SD = 4.71) species respectively predicted through Jackknife 2 and Chao 2 estimations. Plegadis chihi was the most abundant bird roosting in the reserve. The area is important for the conservation of Circus cinereus, Spartonoica maluroides, Limnoctites rectirostris and Sporophila palustris, which are considered threatened or near-threatened in state, national and/or global levels. We emphasize the urgent need of implementing the Reserva Biológica do Mato Grande in order to conserve the regional avifauna.