Data from: Concealed by darkness: interactions between predatory bats and nocturnally migrating songbirds illuminated by DNA sequencing

Recently, several species of aerial-hawking bats have been found to prey on migrating songbirds, but details on this behaviour and its relevance for bird migration are still unclear. We sequenced avian DNA in feather-containing scats of the bird-feeding bat Nyctalus lasiopterus from Spain collected during bird migration seasons. We found very high prey diversity, with 31 bird species from eight families of Passeriformes, almost all of which were nocturnally flying sub-Saharan migrants. Moreover, species using tree hollows or nest boxes in the study area during migration periods were not present in the bats’ diet, indicating that birds are solely captured on the wing during night-time passage. Additional to a generalist feeding strategy, we found that bats selected medium-sized bird species, thereby assumingly optimizing their energetic cost-benefit balance and injury risk. Surprisingly, bats preyed upon birds half their own body mass. This shows that the 5% prey to predator body mass ratio traditionally assumed for aerial hunting bats does not apply to this hunting strategy or even underestimates these animals’ behavioural and mechanical abilities. Considering the bats’ generalist feeding strategy and their large prey size range, we suggest that nocturnal bat predation may have influenced the evolution of bird migration strategies and behaviour.近期研究发现，数种空中捕猎蝙蝠（aerial-hawking bats）会以迁徙中的鸣禽为食，但有关该捕食行为的细节及其对鸟类迁徙的影响仍尚不明确。我们对西班牙境内鸟类迁徙季采集的食鸟蝙蝠Nyctalus lasiopterus的含羽毛粪便样本中的鸟类DNA进行了测序。结果显示该蝙蝠的猎物多样性极高，共检测到雀形目（Passeriformes）8个科下的31种鸟类，其中几乎全部为夜间飞行的撒哈拉以南迁徙鸟类。此外，在研究区域内迁徙期间依赖树洞或巢箱栖息的鸟类并未出现在蝙蝠的食谱中，这表明蝙蝠仅会在鸟类夜间飞行过境时将其在空中捕获。除了广食性取食策略外，我们还发现该蝙蝠会选择性捕食中等体型的鸟类，推测此举可优化其能量成本收益比并降低自身受伤风险。令人意外的是，蝙蝠的捕食对象体重可达自身的一半。这说明传统上认为空中捕猎蝙蝠的捕食者-猎物体重比为5%的结论，并不适用于该类捕食策略，甚至低估了这些动物的行为与机械能力。考虑到该蝙蝠的广食性取食策略以及宽泛的猎物体型范围，我们认为夜间蝙蝠捕食行为或许对鸟类迁徙策略与行为的演化产生了影响。