Long‐term fallows rate best among agri‐environment scheme effects on farmland birds—A meta‐analysis

Agri‐environment schemes (AES) serve to counteract the ongoing decline of farmland bird populations, but their success remains controversial. We conducted a meta‐analysis to compare standardized effect size estimates among European AES options—classified into 15 categories that capture relevant management practices—for farmland bird abundance and species richness. Effect strengths varied substantially between AES categories. Long‐term fallows, nonproductive crops such as wild bird seed mixtures, artificial food supply, and winter cover yielded the strongest positive associations with farmland bird abundance. Average effect sizes were larger but also more variable in cropland compared to grassland‐dominated farming systems. This observation highlights the need to develop more effective conservation schemes for grassland inhabitants, which face similarly severe population declines as cropland inhabitants. Schemes that provided large ecological contrasts between treatment and control sites yielded particularly strong relative benefits, but AES‐specific effect sizes further varied with foraging and nesting site guilds of the target species. Our study confirms that the AES that is currently implemented can benefit farmland birds. However, clear improvements require AES to focus on options with maximal improvements in habitat quality and to locally implement sufficiently diverse AES options to serve the often‐incongruent needs of several bird guilds and species.