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.

中文翻译：

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在农业环境计划对农田鸟类的影响中，长期休耕率最高——一项荟萃分析

农业环境计划（AES）有助于抵消农田鸟类数量的持续下降，但它们的成功仍然存在争议。我们进行了一项荟萃分析，以比较欧洲 AES 选项（分为 15 个类别，捕捉相关管理实践）对农田鸟类丰度和物种丰富度的标准化效应大小估计。AES 类别之间的效果强度差异很大。长期休耕、野生鸟类种子混合物、人工食物供应和冬季覆盖等非生产性作物与农田鸟类丰度的正相关性最强。与以草地为主的农业系统相比，农田的平均效应规模更大，但变化也更大。这一观察强调了为草原居民制定更有效的保护计划的必要性，与农田居民一样面临同样严重的人口下降。在处理和控制地点之间提供较大生态对比的方案产生了特别强的相对效益，但 AES 特定的影响大小随着目标物种的觅食和筑巢地点行会而进一步变化。我们的研究证实，目前实施的 AES 可以使农田鸟类受益。然而，明显的改进要求 AES 专注于最大限度地改善栖息地质量的选项，并在当地实施足够多样化的 AES 选项，以满足多个鸟类行会和物种经常不一致的需求。但是 AES 特定的影响大小随着目标物种的觅食和筑巢地点行会而进一步变化。我们的研究证实，目前实施的 AES 可以使农田鸟类受益。然而，明显的改进要求 AES 专注于最大限度地改善栖息地质量的选项，并在当地实施足够多样化的 AES 选项，以满足多个鸟类行会和物种经常不一致的需求。但是 AES 特定的影响大小随着目标物种的觅食和筑巢地点行会而进一步变化。我们的研究证实，目前实施的 AES 可以使农田鸟类受益。然而，明显的改进要求 AES 专注于最大限度地改善栖息地质量的选项，并在当地实施足够多样化的 AES 选项，以满足多个鸟类行会和物种经常不一致的需求。