Q. I put up a bat house in my backyard but so far there have been no bats! How do I encourage them to make my backyard their home?
A. Bats are one of the most beneficial critters for your yard - especially when it comes to driving down the amount of bugs in your backyard. Did you know that the little brown bat can eat up to a thousand mosquito-sized insects in only one hour? By following these recommendations you should increase the success of attracting bats to your bat house:
- Temperature may be the most important factor in roost selection. In Canada, bat houses should receive at least six to ten hours of direct sun each day.
- Mount bat houses on poles or on the side of a building. Ideally they should be mounted at least 12 feet (4 metres) above the ground although mounting bat houses at 15 feet (4.5 metres) to 20 feet (6 metres) typically garners the best results. You want to avoid mounting bat houses on trees – they are more difficult for bats to find and are more vulnerable to predators.
- Bats choose roosts less than a quarter mile (400 metres) from a water source such as a stream, river or lake.
- Bats like a clear sweep zone to get in and out of their roosts, so avoid placing the house in an area where there are a lot of obstacles, such as tree branches. To discourage predators, bat houses should be placed at least 25 feet (8 meters) from predator perches such as wires and tree branches.
- Placing two or more houses in one location allows bats to better respond to changes in temperature by allowing them to move between the houses as needed.
- Do not mount bat houses close to bright lights.
- For Canada’s summer temperatures, the outside of bat houses should be painted black or dark brown to increase the inside temperature. Paint the outside of the house with three coats of water-based paint or stain, not oil-based. Use two coats of dark, exterior grade, water-based stain for the interior. Apply the stain to the inside only after you have made the scratches or grooves as explained below.
- The inside of bat houses must be roughened to allow bats to grip. Create horizontal (not vertical) scratches or grooves. Space cuts roughly ½ inch (13 mm) apart and 1/16 or 1/32 inch (1 or 1.5 mm) deep. An alternative is to attach plastic (not metal) screening flat on the wood surface to avoid injury to the bats.
- Be sure to use untreated wood when constructing your bat house. Pressure treated wood may contain chemicals that are harmful to bats.
- Be sure to caulk all seams, especially around the roof, to prevent drafts and to help keep temperatures stable.
- Use exterior grade or galvanized screws rather than nails.
- If after two years your bat house has failed to attract occupants, try moving it to a new location.
A few other points to remember:
- Open-bottom houses reduce problems associated with birds, squirrels, and mice and their guano won’t accumulate inside.
- When choosing a spot to install your bat house remember that guano will fall to the ground below the house. Avoid placing bat houses above doors, decks, windows and walkways. Some finishes can also be stained from bat urine. A potted plant placed below the bat house can collect the bat guano.
Get plans on how to build a bat house. Good luck in attracting bats to your property!
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