Northern Prairie Wildlife Research Center
Sometimes bats will temporarily roost in open structures such as porches, garages, and patios or behind shutters, shingles, roof gutters, and trim with overhang. Transient bats in migration, male bats during the nursing season, and foraging bats hanging up at night to rest may find these outside areas attractive and convenient. If bats roost under the eaves of buildings or on other areas outside the house, actual control may not be necessary unless their droppings become a problem. Then some insulation material will probably work. Constantine (1979a) stated that coarse fiberglass batting tacked to the surfaces where bats hang might discourage them. D. G. Constantine stated (personal communication), "It might be worth mentioning that woodpeckers can peck a hole through places like a roof trim to let bats in, too often after exclusion has been performed. I have had to go so far as to recommend covering all trim with sheet metal. Of course, the birds may move down a few inches."