Bat House Forum

[Terry Lobdell]

I have been replacing the brown shingles on my roof with white ones because they last longer. When I was up there today, I found where my big brown maternity was roosting!

[Terry Lobdell]

This is a single crevice, back vent/access house. There are 3/4" spacers which provide a gap for the bats to roost behind when it gets too hot. The top is open between the spacers which allows plenty of ventilation. The spacers also allow easy mounting. Two 3/16" vinyl coated cables are clamped around the chimney and tightened with turn buckles. This box faces directly east. It's about 14" wide and maybe 18" tall including the landing pad. I did an exit count tonight and there was between 30 and 40 that came out. It was hard to do an accurate count because a few bachelors from the other houses were exiting as well. About 10 bats exited out of the top. There is only about 3 - 4 feet of exit space but they did not seem to have trouble. Probably half of the bats that exited out of the bottom only used about 18" below the box for their exit swoop. This is one of 10 different bat houses that this maternity has used this summer. Since it has been successful, I may replace it with a 3 crevice box eventually.

 

[Terry Lobdell]

Here is the guano pile. From the exit count I did tonight, and one earlier this spring, I think my big brown maternity may have grown by a couple mothers. I usually have 15-16 mothers. On May 8th, I had an exit count of 18 adults. But maybe that was early enough that some were bachelors? It has been hard this year know exactly how many big brown mothers I have because they usually are split up into 2 groups. Tonight was a rare night when they were all together. The count I got tonight was definitely closer to 40 than 30, so I'm guessing I have a few more big browns this year!

[Gran]

Will guano pile damage roof?

[IowaNate]

 Excellent news Terry! I can definately see that that house probably isn't checked for occupancy as much as the others.

[Terry Lobdell]

Gran, I'm sure the guano and urine will eat through the shingles. I will probably have to put something different than shingle underneath............maybe I will replace the shingle tabs with pieces of vinyl siding of the same color........

Nate, you are exactly right! I was not expecting this much use from this box either this year.........it was mounted last year and only had bachelor use............I mainly wanted to see if there was enough room for them to exit being mounted so close to the roof.

I was up there today around 1:00pm and all the bats were roosting behind on the chimney brick.

[Terry Lobdell]

I went up and actually did an exit count right up on the roof tonight. It was neat setting up close and watching them come out. There was a total of 34 big browns. About 12 - 15 came out of the top. A couple that came out the top climbed a few inches up onto the brick and pushed off with their feet and got a much higher and faster exit! The ones that came out of the bottom came pretty close to the roof.

Someday maybe I will try to get some video of this.

Sadly I had 3 get down into my chimney and 2 died. I have since closed off the chimney. I had never had that happen before. I should have thought about it though with so many roosting in this box.

A local rehabber said 90% of the pups she gets are big browns. They seem to explore more, fall more and just get lost. Maybe because they require more stable temps.

[Joe Spencer]

Originally it was thought that bats needed far more height to drop and gain flight however, after witnessing a bat house mounted on another chimney roof and being only 1 foot above the roof, it certainly blows that away.  Safety from predators and the other factors are primary issue when it comes to mounting height.  On the house I saw many of the bats would drop out of the bat house and spring-board off the roof to gain flight.  Quite a site.

[Terry Lobdell]

Wow, I've never seen them springboard like that Joe! I've often seen bats exit with only about a one foot drop. Seems like most of the time in general they drop about 5 feet before leveling out. It was very interesting setting up on the roof and watching them close up this summer.

When I started the back vent/access design with the option for bats to exit out of the top from the space behind I thought more bats would do it. Only 10% to 30% do though. I am guessing they prefer diving straight down upon exit for speed in case predators are lurking nearby. It's probably an instinctive thing.

[Terry Lobdell]

My big brown bat maternity is now using this box........the pups should start flying any day now if they haven't already.........I have noticed this same maternity colony has used this box right before pups start to fly other years as well.......

[Terry Lobdell]

Just a note that this box was again used by my big brown maternity colony in 2011.......It is successful because of the gap/space between the box and the chimney which allows a cooler place for them to roost in very hot weather and also because the chimney acts like a heat sink maintaining stable temps in the box........This box would not work at all mounted on a pole.......it would cool down too much at night.........I now only build boxes with a minimum of 3 crevices.......