Bat House Forum

[Kent]

I am beginning to believe air movement in areas near bat houses and in bat houses has much to do with bat house success.

The reason I say this is I do a lot of experimenting with designs and placement of bat houses.

You can take same bat house designs and place them in open areas near trees, where there is air movement and have high success rate. You take same house designs and place them in open areas surrounde d by trees but not a lot of air movement and success rate drops.

Whenever there are octagon roof gazebos with bats in the area over 90% of the time bats will be roosting in the top of the gazebo. There is a lot of air movement on the roofs and under the roofs of octagon shaped buildings and gazebos. This is one of the reasons it is almost impossible to get many years from the shingles on the roof of an octagon shaped building. The air swirls around the roof and lifts the shingles .

It would be interesting to try some octagon shaped bat houses with a tapered eight sided roof . The roofs would not be a problem to saw with a compound miter saw

This fall I am going to make several octagon deign bat houses to test this theory. I will post some pictures and keep you updated on the success or failure of the design.

Kent Borcherding

[Joe Spencer]

Kent glad to hear from you and thank u for sharing this great information. It does indeed make some sense that our little friends need to breath as much as we do. I am assuming that this information is pointing towards fresh air and oxygen levels rather than having anything to do with heat/temp factor.....

[Mark Kiser]

Hi all,

The open space around roosts can definitely be important, but I'm wondering whether it's really an ease of access/ease of maneuvering around the roost/avoiding predators issue rather than actual air movement, since the bats are typically roosting in tight sheltered spaces that minimize drafts. Reducing evaporative cooling and minimizing water loss is a big concern for small insectivorous bats, as they have a considerable amount of surface area (wings and flight membranes) from which they can lose body water. If you point an electric fan at bats in an attic, they will move away or leave. Wide open spaces around the roost make it harder for hawks and owls to swoop down and pick off a bat as it leaves the roost. Nearby branches make for easy raptor meals.
Branches even 15 feet away from a bat house are not very safe.

Cheers,

Mark

[Joe Spencer]

Ok now I'm really confused Kent and Mark. Upon reflection I remember seeing some BCI photos a few years ago of lone small bci bat house (old original design non-nursery) which had hundreds of bats in this bat house. Just the population of bats alone would limit air movement in the upper areas yet the bats were there. So Mark can you confirm that it really isn't an oxygen/air factor? I have seen numerous bats within the walls and insulation at people's homes with little or no air movment or level at all and bats were quite content. Conserving water really makes sense since the bats can be in the diurnal roost for up to 15 hrs. each day before replenishment. Hmmm great stuff here thank's

[Mark Kiser]

Hi Joe,

All the literature I've seen suggests bats seek stable temperatures for nursery sites as a energy conservation strategy. Stable roost temps also mean little air movement within the roost; energy and water conservation would be substantial benefits received from sheltered roost sites. Clustering is another behavioral strategy that helps save water and energy when roost conditions are less than ideal.

Open sites away from trees also have another advantage over cluttered sites---easier for bats to find a bat house, so quicker occupancy time should result.

Cal Butchkoski and John Chenger suggest, however, that bat houses should be located near a treeline (within 50 feet) to offer escape cover, should a raptor key in on bats exiting the house.

In our last annual survey, bat houses did best in open-type sites where the dominant natural vegetation was fields and shrubs (80% success) followed by grasslands (66%), followed by forest (53%).

It would appear that bat houses do very well in open areas regardless of which reason is most important, but there's probably multiple benefits at play here.

Just my humble opinion, could be wrong.

Cheers,

Mark