Batwatching in the daytime

Today I saw a interesting black point in the sky: it wasn't a bird, but it was moving, flying and comming... It was a bat and an other one and the next. I realized just later, that it was a flock of the migratory bats. These animals moved from the breeding area towards the wintering areas, what are somewhere in the mountens, because they roosting in caves, mines. In the bigest wintering caves have thousand of bats: horseshoe bats, Mouse-eared Myotis, Lesser Mouse-eared Bat...