Breeding ground food availability is critical to the survival and productivity of adult birds. The common cuckoo Cuculus canorus is a brood‐parasitic Afro‐Palearctic migrant bird exhibiting long‐term (breeding) population declines in many European countries. Variation in population trend between regions and habitats suggests breeding ground drivers such as adult food supply. However, cuckoo diet has not been studied in detail since before the most significant population declines in Europe began in the mid‐1980s. 20th century studies of cuckoo diet largely comprised field observations likely to carry bias towards larger prey taxa. Here we demonstrate the potential value of 1) using high‐throughput DNA sequencing of invertebrate prey in faeces to determine cuckoo diet with minimal bias towards large prey taxa, and 2) using crowd‐sourced digital photographs from across Britain to identify lepidopteran cuckoo prey taxa during recent years post‐decline (2005–2016). DNA analysis found a high frequency of Lepidoptera, including moths of family Lasiocampidae, prominent within the past literature, but also grasshoppers (Orthoptera) and flies (Diptera) that may be overlooked by field observation methodologies. The range of larval lepidopteran prey identified from photographs largely agreed with those previously documented, with potential signs of reduced diversity, and identities of key adult prey taxa were supported by molecular results. Notably, many identified cuckoo prey taxa have shown severe declines due to agricultural intensification, suggesting this has driven spatial patterns of cuckoo loss. Landscape‐scale, lowland rewilding interventions provide opportunities to understand the scale of reversal of previous agricultural intensification that may be necessary to restore prey populations sufficiently to permit recolonization by cuckoos.

中文翻译：

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使用分子和众包方法评估具有保护意义的迁徙亲虫的繁殖基础饮食

繁殖地面食物对成年鸟的生存和生产力至关重要。杜鹃Cuculus canorus是一种在欧洲许多国家中具有长期（繁殖）种群减少趋势的，寄生于非洲的非洲古移民鸟。区域和栖息地之间人口趋势的变化表明，诸如成人食物供应之类的繁殖地动因。然而，自从1980年代中期欧洲最显着的人口减少开始之前，就没有对杜鹃的饮食进行过详细的研究。杜鹃饮食的20世纪研究主要包括实地观察，可能会偏向大型猎物类群。在这里，我们证明了以下方面的潜在价值：1）使用粪便中无脊椎动物猎物的高通量DNA测序来确定布谷鸟饮食，而对大型猎物类群的偏向最小，以及2）使用来自英国的众包数码照片来识别鳞翅目布谷鸟猎物类群下降后的最近几年（2005-2016年）。DNA分析发现鳞翅目的发生频率很高，包括在过去的文献中很突出的鳞翅目科的飞蛾，还有可能被野外观察方法忽略的蝗虫（直翅目）和苍蝇（双翅目）。从照片中鉴定出的幼虫鳞翅类猎物的范围与先前记录的照片基本吻合，具有减少多样性的潜在迹象，并且分子结果支持了主要成年猎物类群的身份。值得注意的是，由于农业集约化，许多已查明的杜鹃猎物分类单元已显示出严重下降，这表明这推动了杜鹃的空间分布。景观尺度