Simple Panel Bat Houses

Bat houses don't need to be complex to be successful. By adding a large board or piece of plywood to an existing structure, you may be able to create an ideal roost site. Simple and inexpensive, yet large, single-chamber bat houses can be made from quarter, half, or full sheets of 1/2-inch-thick (or thicker) exterior grade plywood and 1-inch by 2-inch (3/4-inch by 1 3/4-inch finished) furring strips for spacers. Ideal mounting sites are wooden or masonry structures such as barns, bridges, silos, or other buildings. Depending on the mounting substrate, a landing area may not be necessary. Bats can simply land on the structure below the bat house and enter, if the surface is rough enough. Remember to follow painting, venting, solar exposure, and mounting height recommendations.

When California farmer Cliff Fong found several bats roosting under the eaves of his barn, he recognized their beneficial qualities. He created additional roosting space for them by adding a 1-by-6-foot board onto an existing beam near where the bats were roosting. His simple bat house now provides shelter for several hundred Mexican free-tailed bats (Tadarida brasiliensis) and Yuma myotis (Myotis yumanensis).

Lee Christenson of Strum, Wisconsin, "advertises" for bats with two large but simple, two-chamber bat houses on his warehouses. Each bat house consists of three sheets of 1/2-inch plywood, covered on one side by plastic mesh and separated by furring strip spacers. With his company logo painted on the front, the houses appear simply as signs. In the first year, just two little brown bats (Myotis lucifugus) moved in, but he is hopeful that more will be attracted next year. Such signs often have unintentionally provided homes for hundreds of bats.

After Edward Freeman of Gardiner, Maine, discovered that his small nursery bat house had attracted more than 25 bats, he constructed a large, single-chamber bat house directly onto the outside wall of his woodworking shop to attract even more.

This large bat house was installed on the south wall of the 20- by 24-foot wooden shop for maximum warmth. The basic components are two full sheets of 1/2-inch-thick plywood (4 feet by 8 feet) separated by 3/4-inch wooden strips along the top and sides. An additional 3/4-inch thick spacer in the center prevents warping. A 1/2-inch layer of Styrofoam insulation was attached to the front before it was covered with vinyl siding to match the building's exterior.

"My desire is to have homes for hundreds of bats to replace all the old barns and other roosts that no longer exist," explains Freeman. "Sixty years ago it wasn't necessary to spray large tracts of forest and gardens to keep insects under control. My 70 bird houses made a big difference on the daytime insects, and I want as many bats as possible to take care of the nighttime insects as well!"

His hard work is beginning to pay off. For the past two years the woodshop house attracted a small colony of 10-15 bats, while his nursery house colony has grown to between 50 and 100 bats. We suspect that the insulation and light exterior are keeping the woodshop roost a bit too cool for nursery use, perhaps explaining why so far, there is only an apparent bachelor colony. The small nursery house, painted black, has been much more successful. Future experiments should probably avoid insulation and include a darker, heat-absorbing exterior. Freeman plans to install temperature probes in the bat house and shop next year and may remove the insulation after comparing the temperatures.