With Halloween just around the corner, I’ve got bats on the brain. After participating in a night mission to monitor bat activity with the Conserve Wildlife Bat Project, I’ve become hooked on the bat cause. Brian Henderson and Ben Wurst, a.k.a. reclaimednj, of the Conserve Wildlife Foundation of New Jersey have compiled instructions on how to make your own bat house. It’s important to help your local mosquito-swilling bats find refuge, as many bat populations are dwindling at an alarming rate. This weekend project is perfect for using up scrap lumber and doing your part for nature conservation.
Conserve Wildlife Foundation of New Jersey is a non-profit organization dedicated to protecting New Jersey’s more than 70 endangered and threatened species and the habitats on which these animals depend. Our work is accomplished through biological research, rare wildlife management and habitat restoration, education and outreach.
Bats are getting a lot of attention these days, and it isn’t just because they can eat thousands of mosquito-sized insects each night, providing helpful insect control without the use of pesticides; their numbers are dropping rapidly. This trend isn’t unique to New Jersey, as more than half of America’s bat species are in severe decline. Bats have long suffered the effects of habitat loss and disturbance to their hibernating colonies and summer roosts. The newest threat is a disease called White-Nose Syndrome. First discovered in a New York cave in 2006, White Nose Syndrome has spread further south and west each year and has since devastated populations of cave-dwelling bats in 19 U.S. states.
Conserve Wildlife Foundation of NJ is involved in numerous projects to study and protect bats by organizing an annual Summer Bat Count, surveying bat caves and maternity colonies, using car-mounted acoustic bat detectors to “hear” and monitor bat activity statewide and working with landowners to enhance bat habitat on private property.
Many people are concerned about the declining bat populations and want to help. While some threats are out of our control, building and installing bat houses is a simple way to give local bat populations a bit of help by providing them with secure places to rest and raise their young. There are lots of variations on how to build a bat house. This how-to is adapted from instructions from the Pennsylvania Game Commission’s design and will show you how to create a three-chamber bat house that provides a summer roosting habitat for up to 100 bats.
To learn more about Conserve Wildlife Foundation of NJ or to become involved in any of our volunteer-based projects, visit our website.
Supplies you’ll need:
- 8 pieces of pre-cut wood (3/4” plywood) — You can use exterior plywood, cedar or pine to build your house, but should avoid using pressure-treated wood.
- Back = 18” x 24”
- Front top = 9” x 18”
- Front bottom = 5 ½” x 18”
- Roof = 6 ¾” x 19” (one end of the 19” side to should have a 45° angle)
- 2 baffles = 14” x 16” — Before assembly, the baffles (vertical pieces of wood that divide the interior of the box and provide increased surface area for the bats to cling to) and other interior surfaces should be roughened and scratched to create textured surfaces for the bats to climb and hold onto. This can be done with the claw-end of a hammer, a table saw, or whatever other method you find convenient.
- 2 sides = 21” long 2x4s with ends cut at a 45° angle (short end will be ~15”). Use a router to create two grooves ½” wide and ½” deep to hold the baffles in place. Grooves should begin 1” and 2 ¼” from the longer (21”) side.
- Roofing material – approximately 7” x 19”
- Screening – approximately 5” x 13”
- 38 screws – 1 ¼” wood or galvanized drywall screws (1LB)
- Staple gun
- Philips Head Screwdriver (or power drill & drill bit)
- Caulk gun
- Roofing tar or caulk
- Liquid Nails
- Exterior water-based paint. The color will be dependent on your climate. (See step #14 for details)
1. Apply a thin strip of Liquid Nails or wood glue to the long side of each 2×4.
2. Lay the side pieces across from one another, making sure the grooves face each other. It can be helpful to place one of the baffles between the side pieces to make sure you have the proper spacing.
3. Place the back piece on top of the side pieces, making sure the edges are aligned on the bottom and sides of the back.
4. Attach the back to the sides using six evenly spaced screws on each side. We recommend pre-drilling each hole using a 1/8″ drill bit. Use an electric drill or Philips head screwdriver to secure each screw.
5. Turn the box over and apply a thin strip of adhesive to the top of each side piece and across the top of the bat house, where the sides and back meet. You can tell the top because the back will extend past the sides, leaving you space to attach the roof.
6. Center the roof over the side and back. The beveled edge of the roof should fit snugly against the back of the box.
7. Secure the roof, using three screws on each side.
8. Center the screening about one inch from the bottom of the box and attach by stapling around the perimeter. This will provide the bats with a good surface to grab onto.
9. Slide the baffles into the grooves on the interior of the bat box. If the fit is tight, you can use a block of wood and hammer to knock them into place. Position them so that they are each at least 1″ from the top and offset from one another.
10. Measure approximately 5 inches from the top of the box and put one screw in each baffle (two on each side) to hold them in place. Do this on both sides.
11. Apply a thin strip of adhesive to the top edge of each side. Place the top (larger) front piece so that the beveled edge is snug with the roof. Secure it in place with three screws on each side.
12. Do the same for the bottom front piece, making sure to leave a gap of at least 1/2″ between the top and bottom boards. This space helps prevent the box from overheating on hot days. Secure in place using two screws on each side.
13. Seal all the edges and screw holes with caulk to protect from rain and poor weather.
14. When your bat house is complete, paint all exterior surface with an exterior grade water based paint. Where you live will determine what color you should paint your bat house. Where average high temperatures in July are less than 85° F, black paint should be used; where temperatures are 85° to 95°, dark brown or dark grey colors should be used; where temps are 95° to 100°, medium colors should be used, and where temps exceed 100° in July, white or light colors should be used. A lot depends on the amount of sun exposure; use a darker color if sun exposure is weak. The bat house needs to retain heat, which is important for the bats and their young pups.
15. Lightly cover the top of roof with adhesive and place roofing material flush against the back. The roofing will overhang on the front and sides; staple around the perimeter in order to secure it to the roof. Staples should be covered with roofing cement before hanging.
16. Install your finished bat house! Proper site selection is the key a successful bat house. Your house should be placed at least 12 feet above the ground in an open area where it will receive at least 7 hours of direct sun each day, preferably facing south-southwest. It should also be within about ¼ mile of a reliable drinking source such as a stream or pond, and within 100 feet of a tree line to provide cover from aerial predators.
The best place to hang your box is on a pole or building in a spot where “people traffic” is low. Placing it on a tree is not recommended because they are often too shaded and are also more accessible to predators. If a tree is your best option, place a metal predator guard around the tree below your bat house.
Bat houses can be built and installed at any time of the year, but are more likely to be used their first summer if installed before spring. When using bat houses in conjunction with excluding bats from a building, install the bat house at least a few weeks before the eviction is performed.