Livestock production and the replacement of semi-natural grasslands by crops result in land use changes and as consequence some habitat is no longer suitable for all species of grassland birds. Although some generalist species could benefit from such changes, habitat alteration is detrimental to the populations of most sensitive species. In this study, we investigated the patterns of habitat use by breeding grassland birds through the assessment of their presence/absence and abundance in a landscape composed of semi-natural grasslands and croplands in southern Brazil and Uruguay. We sampled grassland birds in 160 100-m radius point counts: 80 in a semi-natural grassland dominated landscape and 80 in soybean fields with grassland patches. We classified vegetation cover on a 100-m radius buffer following three classes of land use: semi-natural grasslands, wet grasslands, and soybean fields. We used GLMM to analyze presence/absence and abundance of grassland birds found in the region. Nine species showed a positive response to the semi-natural grasslands and/or wet grassland vegetation cover categories. Five species recorded are of conservation concern. Most of the grassland bird species preferred sites with high semi-natural grassland cover and only one species used primarily soybean fields. Grassland birds required around 80% of semi-natural grassland cover to maintain larger abundances. Research across landscapes and a better understanding of the responses of grassland birds to habitat modification are still needed to establish conservation practices of natural grasslands and their avifauna in southern Brazil and Uruguay.