Summer: Bat House
The hottest place to hang out.
Bats like to roost in groups in warm, close spaces. A simple bat house situated to catch plenty of the sun's warming rays will encourage these voracious mosquito-eaters to hang out around your yard. You'll enjoy watching bats cruise for 'skeeters while the sun goes down, knowing their every chomp is saving you from an itchy bite. This house has one roosting chamber. Other designs in Bat Conservation International's "Bat House Builder's Handbook" sandwich several roosting chambers together into bat colony condos!
What You'll Need
- one 2' x 4' (one-quarter sheet) of ½" exterior grade plywood
- one piece 1 x 2 (about ¾" x 1½") x 8' pine furring strip
- one piece wood 1" x 3" x 28" for roof
- 20-30 coated deck or exterior grade Phillips-head screws 1-1/4"
- 1 pint water-based exterior stain, in a dark color
- 1 pint water-based exterior primer
- 1 quart flat water-based exterior grade paint or stain
- 1 tube paintable latex caulk
- Black asphalt shingles or galvanized sheet metal
- six to eight 7/8" roofing nails
- Measure and cut plywood into three pieces:
26 ½" x 24"
16 ½" x 24"
5" x 24"
- Roughen inside of back board and landing area by cutting horizontal grooves with a sharp object or saw. Space grooves about ½" apart, cutting 1/16" to 1/32" deep. (The rough surface provides traction, giving the bats something to grip on to while hanging.)
- Apply two coats of dark, water-based stain to interior surfaces. Do not use paint, as it will fill grooves, making them unusable.
- Measure and cut furring strip into one 24" and two 20¼" pieces.
- Attach furring strips to back, caulking after screwing in strips. Start with 24" piece at top. Roosting chamber will be ¾" wide (front to back).
- Attach front to furring strips, top piece first (don't forget to draw a bead of caulk on the top edge of the furring strip before driving the screws). Leave ½" vent space between top and bottom front pieces.
- Caulk around all outside joints to further seal the roosting chamber.
- Attach the 1" x 3" x 28" board to the top as a roof.
- Paint or stain exterior three times (use primer for first coat).
- Cover roof with shingles or galvanized metal and attach with roofing nails.
Mounting & Maintenance
In early spring, mount the bat house on the side of a building at least 12 feet (15 to 20 feet is better) above ground, in a spot where it will receive sun all day long. A spot under the eaves is ideal. To create favorable conditions for a summer breeding colony, the internal temperature of the bat house should stay between 80 to 100°F for as long as possible. Bat houses can be placed back-to-back and mounted on a pole, but those mounted on buildings gain heat faster, hold it longer, and are more likely to attract bats.
If you're near a stream, river or lake, there's a good chance bats will find and colonize your bat house relatively quickly.
Maureen Mecozzi is a contributing editor to Wisconsin Natural Resources magazine.