Great question! Bats are not keen on being out in the day, mainly because there is a higher risk of predation from birds of prey. Bats have evolved for many millions of years to exploit ecological niches at night. They are experts at hunting insects in the air in complete darkness, and therefore avoid competing with birds that feed on insects during the day. Over those millions of years they have become so well adapted to being active at night that they don’t need to come out in the day.