Military areas often host extraordinary biodiversity compared to the typical agricultural landscape in Europe. It has been suggested that this is due to the high landscape heterogeneity caused by disturbances from military training. This study aimed to test this hypothesis using data from the military area Hradiště and nearby farmland in the Czech Republic (Central Europe). Here, we measured two facets of landscape heterogeneity – the number of woody vegetation patches and habitat diversity – and supplemented these measures with previously published data from bird point counts performed on the same sites. The number of woody vegetation patches was higher in the military area than in the farmland and was positively related to the species richness of birds of conservation concern. Habitat diversity did not differ between both regions. It showed, however, a hump-shaped relationship with total bird species richness. Our results indicate that open landscapes of military areas host a higher number of birds of conservation concern than the farmland due to a finer grain of woodland-grassland mosaic. To support more bird species, it is essential to keep habitat diversity high in open landscapes but at a level that does not harm bird populations by area limitation.