The extent to which prey traits combine to influence the abundance of predators is still poorly understood, particularly for mixed predators in sympatry and in aquatic ecosystems. In this study, we characterise prey use and distribution in iconic bird (grey wagtails and Eurasian dippers) and fish species (brown trout and Atlantic salmon) to assess whether prey traits could predict populations of these four riverine predators. Specifically, we hypothesised that: 1) prey key traits would predict predator populations more effectively than 2) diversity of prey traits, 3) the taxonomic abundance or richness of prey (known as traditional or mass‐effect types of biodiversity) or 4) the prevailing environmental conditions. Combined predator population sizes were predicted better by a few key traits – specifically those revealing prey habitat use, size and drifting behaviour – than by prey diversity or prey trait diversity or environmental conditions. Our findings demonstrate that the complex relationships between prey assemblages and multiple predator species can be represented mechanistically when the key prey traits that govern encounter and consumption rates are identified. Given their apparent potential to reveal trophic relationships, and to complement more traditional measures of prey abundance, we advocate further development of trait‐based approaches in predator–prey research.

中文翻译：

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高价值捕食者的种群反映了其捕食者的特征

猎物性状在多大程度上影响捕食者的数量，仍然知之甚少，特别是对于共生和水生生态系统中的混合捕食者。在这项研究中，我们表征了标志性鸟类（灰w和欧亚北斗）和鱼类（褐鳟和大西洋鲑）中的猎物使用和分布，以评估猎物特征是否可以预测这四个河道捕食者的种群。具体来说，我们假设：1）猎物的主要特征比2）猎物的特征更有效地预测捕食者的数量，3）猎物的分类学丰度或丰富度（称为传统或生物多样性类型的生物多样性）或4）当时的环境条件。通过一些关键特征，更好地预测了捕食者的总和，特别是那些揭示了猎物栖息地用途的特征，大小和漂流行为–而不是猎物多样性或猎物特质多样性或环境条件。我们的发现表明，当确定支配遭遇和消耗率的关键猎物特征时，可以机械地表示猎物组合与多种捕食者物种之间的复杂关系。鉴于它们具有揭示营养关系并补充更丰富的传统猎物测量方法的潜在潜力，我们主张在捕食者－猎物研究中进一步发展基于特征的方法。我们的发现表明，当确定支配遭遇和消耗率的关键猎物特征时，可以机械地表示猎物组合与多种捕食者物种之间的复杂关系。鉴于它们具有揭示营养关系并补充更丰富的传统猎物测量方法的潜在潜力，我们主张在捕食者－猎物研究中进一步发展基于特征的方法。我们的发现表明，当确定支配遭遇和消耗率的关键猎物特征时，可以机械地表示猎物组合与多种捕食者物种之间的复杂关系。鉴于它们具有揭示营养关系并补充更丰富的传统猎物测量方法的潜在潜力，我们主张在捕食者－猎物研究中进一步发展基于特征的方法。