1. The Common Agricultural Policy (CAP) of the European Union implements several farmland eco-schemes, but most are considered ineffective in halting the population declines of farmland birds. Sown flower fields are among the few eco-scheme types that rate as clearly beneficial. Yet, current CAP regulations lack minimum criteria for flower fields to qualify as eco-scheme, and thus only partially exploit their potential biodiversity benefits.

2. Earlier research on the attraction of farmland birds to different types of sown flower fields has focused on the breeding season. We know far less about relative use of these fields during the non-breeding season, when food limitation can become severe. We therefore compared the attractiveness of four flower field types in SW Germany to 17 bird species during autumn and winter. Based on replicate surveys on 75–168 fields, we analysed bird incidences across these four types, and in relation to vegetation structure and landscape features.

3. Flower field types showed little variation in species richness, but striking differences in selection by particular species. Finches and tits were disproportionally abundant on fields in their first year since sowing, buntings and whinchat on fields in later successional stages. Most flower fields established under CAP greening regulations were ploughed between September and November of their first year. Therefore, such fields cannot support farmland birds and other wildlife during a critical phase in their annual cycle.

4. Birds were consistently more abundant on larger fields with a differentiated vegetation structure. Flower fields along hedgerows and groves primarily attracted inhabitants of woodland ecotones, while farmland birds had higher incidences on fields embedded in open landscapes.

5. 'Policy implications'. EU member states currently revise their farmland eco-schemes. We propose to formulate minimum quality standards to assure that flower fields effectively support farmland birds also during the non-breeding season. These include an at least biennial cycle, more diversified seed mixtures, field sizes exceeding 12 m width or 0.18 ha area, and local diversity in their placement relative to other landscape elements such as hedgerows.