Signs of Spring Everywhere Signs of Spring Everywhere

Build a Bat House!

This bat house was designed by Minnesota DNR Wildlife Manager Earl Johnson. So it's called the "Johnson bat house." Click on it and you can see a bigger version.

Bats often nest in bat houses. You can buy bat houses from gardening and bird feeding stores, or you can build your own. Carrol L. Henderson, who directs Minnesota's Non-Game Wildlife division of the Department of Natural Resources, wrote a great book about building houses for birds and mammals, Woodworking for Wildlife. He says that to building bat houses is a great idea because many species eat mosquitoes, and hunt at exactly the time of day that mosquitoes are most active. Carrol notes that a single big brown bat can eat 3,000 to 7,000 insects each night!

Carrol says that the most likely bats to use houses are the big brown bat and the little brown bat. Do either of them live in your area?

He says that to increase your chances of getting bats to move into your box, the 1-inch width of the entry space is critical. Also he says the inner surfaces must be roughened with a chisel or saw cuts, which will help bats to climb easily. Rough outer surfaces are also preferred.

We humans get uncomfortable in hot rooms, but bats apparently like them, as long as they're not too hot. Carrol notes that daytime temperatures in a bat house should be about 80 or 90 degrees Fahrenheit. He suggests covering the top of the bat house with two or more layers of tar paper, and says it's a good idea to extend the tar paper a couple of inches down the sides. Stapling is a good way to do this. The black color will not only absorb heat to keep the house hotter, it will also protect the bat house from rain. Painting a bat house black works, too.

Carrol says bat houses should be securely fastened to a tree trunk or the side of a building, 12-15 feet above the ground. Make sure a grownup helps put it up! The best place is on the east side of a tree or building, where it will get morning sun but not get TOO hot in the afternoon! Protection from the wind is a good idea, too.

The best habitat for bat houses is near rivers, lakes, bogs, or marshes where insects are abundant. The closer the house is set to great habitat the more likely it is that bats will move in. It's a good idea to set up bat houses by early April, but sometimes it takes a year or two for bats to move in.

There are different kinds of bat houses. Here are two great plans from Carrol Henderson's book, Woodworking for Wildlife.

If you set out a bat house, let us know if you get bats!

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