Context: The loss of landscape heterogeneity is causing declines of farmland biodiversity around the world. Traditional farmland regions are often highly heterogeneous and harbor high biodiversity, but are under threat of land cover homogenization due to changing agricultural practices. One species potentially affected by landscape homogenization is the Corncrake (Crex crex), which is threatened in Western Europe but remains widespread in the traditional farmland regions of Eastern Europe. Objectives: In this study we present a case study aiming to assess the potential threat of landscape homogenization for the Corncrake in Romania. We first examined current Corncrake distribution in relation to woody vegetation cover, landscape heterogeneity, and topography (measured at three different spatial scales), as well as human disturbance, throughout the existing agricultural mosaic. Second, we predicted potential future distribution of suitable Corncrake habitat in response to land cover homogenization by simulating a reduction in land cover diversity. Results: Corncrakes were present in grassland and arable fields, and preferentially occupied remote areas that were wet and flat, and had high land cover diversity at the 100 ha scale. The simulation of land cover diversity loss revealed that even a moderate reduction of land cover diversity could drastically reduce the extent of suitable Corncrake habitat. Conclusions: Our findings show the high conservation value of traditional heterogeneous farmland for the Corncrake. Therefore, to protect the Corncrake in traditional farmland, pro-active policy measures should encourage the continuation of mixed farming practices to maintain a diversity of land covers.