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Truth Muller with a bat box
photo by Bob Muller |
March is the cusp of hibernation for most North American bats. Winter is nearly over, and warmer temperatures will soon give a signal for the bats to wake from their deep sleep. Bats of many species will emerge from their caves and crevices to grab the first bite of food they will have tasted in over six months. The females will gather in barns, attics, and under bridges en-masse to form maternity colonies; It’s pup season in the bat world. The males will head to the forests around rivers, lakes, streams and wetlands, to reap the explosion of newly hatched insects. For hibernating bats, spring means life has begun again.
But for some of these bats, they will find the world today is not the same as the one they went to sleep with. They will find that trees have been clear cut, barns torn down or collapsed, and the entrances to homes sealed up to keep them out. After the catastrophic die-offs caused by White Nose Syndrome, the greatest threat bats now face is loss of habitat.
Just like bluebird boxes give our state bird a place to live, a bat box gives bats new housing. But where a birdhouse holds, at most, a pair and their eggs, a single-chamber bat box can hold 150 to 200 winged tenants! The instructions in this article are for a two-chamber box, with an even larger capacity.
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Bat box bottom view
photo by Bob Muller |
Dimensions: Back: 32” X 9”, Front: 21” X 9”, Sides: 27” X 2 ¼”, Partition: 21” X 7 ½”, Roof: 10” X 5 ¼”, Rear Screen: 27” X 7 ½”, Partition Screen: 21” X 7 ½”
You will need the following: ¾” untreated pine boards, “Pet Screen” (it’s much stronger than regular window screen, and metal screen can hurt them), galvanized screws, silicone caulking, paint primer, and black or dark brown paint.
1. Once all wood is cut to size, paint both sides of the back piece.
2. Attach “Pet Screen” to the back piece and partition with a staple gun.
3. Attach sides to the back piece, leaving 5” at the top (the extra 5” is for mounting the box).
4. Attach partition (screen side forward), leaving 6”on the bottom (for a landing pad for the bats and enough space to secure the bottom to a tree or post). I have found it easiest when spacing the partition between the back and the front (¾” from the back and ¾” from the front, bats like tight spaces), to just lay a ¾” scrap on the back piece and rest the partition on it. Once the partition is secured to the sides, just slide the “spacer” board out.
5. Attach front piece, again leaving 6” on the bottom.
6. Attach the roof, leaving ½” on either side of the box (this helps to keep water from running directly down the sides of all the box, which can cause mold.
7. Caulk all seams.
8. Prime and paint entire box (as I said in step one, paint both sides with the screen on. I learned this the hard way).
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Charlie Hyden installing
his bat box 22 feet high.
photo by Kate Hyden |
Hang your box between 10 and 20 feet up (the higher the better) on a high wall, post or if you have no other option, on a tree. For tree mounting, it is best to have a tree where the branches are sparse and higher than the box, because branches interfere with chances of a bat finding and roosting in it. There is no confirmed way to attract a bat to your bat box. It’s basically the same with all real estate, location, location, location. If it is suitable for the bats to roost in, they will come. In return for your efforts, you’ll get unparalleled free insect control, and years of one of nature’s greatest spectacles: watching bats swooping through the summer night sky.
 — Truth Muller
Warblings, Spring 2016
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