1. Despite large conservation efforts to halt the loss of farmland biodiversity in Europe, negative population trends are still observed, especially for common species. Old villages and human settlements are biodiversity hotspots and important breeding habitats for farmland birds, but recent requirements for energy saving measures and improved living comfort have changed their architecture and habitats. Consequently, modernisation of villages may negatively affect bird diversity due to the loss of nesting and foraging sites.

2. We investigated how the abundance and diversity of birds breeding in 104 Polish villages varied in relation to the degree of modernisation as estimated by the proportion of new and renovated homesteads.

3. Abundance of building-nesting species, but not tree-nesting species, declined by 50% across a gradient of old to highly modernised villages. The contribution of new vs. renovated houses to the observed decline was similar.

4. Applications and synthesis. Rural modernisation has a dramatic effect on abundance of birds nesting in/on buildings, thus may be an important and overlooked contributor to farmland bird population declines in Europe. Villages and rural properties may fall outside of current conservation policy as they are neither protected areas nor agricultural lands (where AES can be applied). Therefore, bird diversity declines in rural landscapes could continue unchecked. The observed conflict between sustainability goals such as increased building energy efficiency and biodiversity conservation suggests that sustainable rural development should better link modernisation with conservation measures, e.g. by constructing nesting sites when renovating and building new houses.