Serotine bats are relatively large bats. They leave their colony later in the evening than the common noctule, which explains its Dutch name 'late flyer'. People often mix up these two species because they are about the same size. You can see serotines flying in the twilight around street lanterns, along the edges of woods and above water. They are busy hunting insects. During the day, the bats are found in buildings, in cavity walls, under roof tiles, behind partitions and in attics. They rarely fly further than 3 kilometers from their roosting sites. Serotines usually spend the winter close by their roosting site.