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.