Modified Beginner's Houses Succeed in Idaho

Bill and Jenni Blair of Cascade, Idaho, built four beginner's bat houses from 3/4-inch plywood, following the Bat House Builder's Handbook plans, but with two alterations: they added Reflectex insulation, in both front and back, and they made two houses without vents. The insulation was used on the inside, lined only with fiberglass window screening. All houses were painted dark brown and mounted in pairs, one vented and one unvented per pair.

The Blairs put up their houses in March, and by June what appeared to be little and big brown bats had moved in, at least 32 and 22 bats each in the unvented houses, compared to 18 and 10 for the vented houses. Since the comparisons turned out not to be identical (one pair was at slightly unequal height, and the other pair received differing amounts of sun), the Blairs will make further tests in the coming season. They also intend to test the bats' preferences for house size by providing large nursery houses, one on the building and a pair on poles nearby.

The Blairs live near a large lake in an area where typical daytime high temperatures in July and August are between 75° and 85°, rarely exceeding 90°. Extensive logging of the surrounding conifer forests may have depleted natural roosts; bats have lived in the Blairs’ cabin walls for generations. But this year, noise in the walls was substantially reduced after bats were seen occupying the bat houses.