Bats are attracted to roofs, chimneys, soffit, and attics for a few reasons. Bats hunting for roosting locations for shelter or warmth.  They are also attracted to areas close to food sources.  Large street lamps attract large amounts of inspects at night and can draw a bat's attention.  Retention ponds have a large number of insects that a mosquito can easily skim off the water's surface.  Destruction of natural habitats can also force bats to seek shelter in man-made structures.