Data from: Combined measurements of prey availability explain habitat selection in foraging seabirds

Understanding links between habitat characteristics and foraging efficiency help to predict how environmental change could influence populations of top-predators. This study examines whether measurements of prey (clupeids) availability varied over stratification gradients, and determined if any of those measurements coincided with aggregations of foraging seabirds (common guillemot Uria aalge, Manx shearwater Puffinus puffinus) in the Celtic Sea, UK. The probability of encountering foraging seabirds was highest around fronts between mixed and stratified water. Prey were denser and shallower in mixed water, and encounters with prey most frequent in stratified water. Therefore, no single measurement of increased prey availability coincided with the location of fronts. However, when considered in combination, overall prey availability was highest in these areas. These results show that top-predators may select foraging habitats by trading-off several elements of prey availability. By showing that top-predators select areas where prey are switching between behaviours, these results also identify a mechanism that could explain the wider importance of edge habitats for these taxa. As offshore developments (e.g. marine renewable energy installations) change patterns of stratification, their construction may have consequences on the foraging efficiency of seabirds.厘清生境特征与觅食效率之间的关联，有助于预测环境变化如何影响顶级捕食者的种群动态。本研究探究了猎物（鲱科鱼类（clupeids））的可获得性是否随层化梯度发生变化，并明确了上述猎物可获得性指标中是否存在与英国凯尔特海海域内觅食海鸟集群——普通海鸠（Uria aalge）、曼克斯剪水鹱（Puffinus puffinus）——相吻合的情况。觅食海鸟的遇见概率在混合水层与层化水层之间的海洋锋面区域最高；混合水层中的猎物密度更高且分布更浅，而层化水层内的猎物遇见频率则更高，因此单一的猎物可获得性提升指标无法与锋面区域的位置相匹配。但当综合多项指标考量时，上述区域的整体猎物可获得性最高。本研究结果表明，顶级捕食者可能通过权衡猎物可获得性的多项维度来选择觅食生境；本研究证实顶级捕食者会选择猎物行为发生转换的区域，这一发现也阐释了一类可用于解释边缘生境对该类群生物普遍重要性的机制。随着近海开发活动（例如海洋可再生能源装置）改变层化模式，这类工程的建设可能会对海鸟的觅食效率产生影响。