Bats emit echolocation calls to orientate in their predominantly dark environment. Recording of species-specific calls can facilitate species identification, especially when mist-netting is not feasible. However, some taxa, such as Myotis bats are hard to distinguish acoustically. In crowded situations where calls of many individuals overlap the subtle differences between species are additionally attenuated. Here we sought to non-invasively study the phenology of Myotis bats during autumn swarming at a prominent hibernaculum. To do so...