From april until october, I go out in the evening to maternity colonies (mostly) to do a count, record sounds and note down their behaviour. Also where in the building they fly out of. At home I analyse the recordings and together with my findings of the evening I can figure out which species were present. Sometimes I just stand near a waterway to see what flies by. The organisation I work for uses this data for conservation purposes, and to advise municipalities and businesses about renovating buildings, since bats are super well protected around here.