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Mark Kiser
Member
| Joined: | Tue Mar 12th, 2002 |
| Location: | Austin, Texas USA |
| Posts: | 58 |
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Posted: Wed Jun 1st, 2005 06:54 pm |
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Sand Gives Bat Houses a New Twist
By Mark & Selena Kiser
One drawback to conventional bat houses is that temperatures inside the roost chambers can sometimes fluctuate dramatically, forcing bats to expend considerable energy in order to maintain their body temperature. In an effort to create a more thermally-stable bat house, Bat Conservation International helped Marvin Maberry of Maberry Centre Bat Homes design and test a new type of bat house. Maberry, an innovative bat house manufacturer and long-time volunteer with BCI?s Bat House Project, developed a prototype in fall 2002 called the Belfry Tower II ?Sand Box.? This was a plastic-stucco rocket-style house with a unique feature--an outer reservoir at the top (surrounding the upper roosting area) that could be filled with 12 pounds of dry sand. The first Sand Box was occupied by two big brown bats (Eptesicus fuscus) the first night after installation in Cason, Texas and the colony grew to 30 bats within six months.
Several more of these prototype houses were shipped to other test sites for comparison with similar plastic-stucco rocket boxes (without sand) built by Maberry. Kent Borcherding, a veteran bat house volunteer in Wisconsin, observed up to 30 little brown myotis (Myotis lucifugus) in a Sand Box in summer 2003, and by summer 2004, there were more than 100, compared with 20 to 80 bats each in the adjacent, unmodified rocket boxes.
In 2003, volunteer Patricia Otto in northwestern Washington observed that her Sand Box received greater use by a colony of long-eared myotis (Myotis evotis) than three other plastic-stucco rocket boxes and four of her six wooden rocket boxes. Nearly two-thirds of her bat colony used the Sand Box in July, and bats used this house continuously from the end of May through August. The other nine boxes were only used a few days or weeks at a time.
The only downside to Maberry?s prototype was that it was more fragile than his other Belfry Tower models and often damaged in shipment. He went back to the drawing board and designed two additional houses, one that holds six pounds of sand in tubes on the inside (?4-tube Sand House,? see below), and another (?Sand Box II?) that holds 11 1/2 pounds of sand in an internal cavity surrounding the upper roosting area. In November 2004 at Marvin?s home, he observed more bats in his ?4-tube Sand Houses? than his standard Belfry Tower houses, presumably due to the added temperature stability. If you are interested in receiving more information about these models, please contact Marvin Maberry at http://www.maberrybat.com.
For the full article and photos, visit this address or click on BCI's free electronic newsletter archives
http://64.92.119.63/news2/scripts/article.asp?articleID=81&newsletterID=9
http://www.batcon.org/home/promo-enewsletter.html
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brockbat
Member
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Posted: Sun Jun 5th, 2005 01:50 am |
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What a great idea using sand as a heat sink. As a northern climate bat lover I've been thinking of what to use as a heat sink as our nights are cool. Could I fill one of the chambers in nursery house with sand? Not sure if front or rearmost chamber would be most effective. Or better yet make a five chamber house and fill the center chamber with sand or pour concrete into it during building. Let me know what you all think.
Brockbat.
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kent borcherding
Member
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Posted: Fri Jun 10th, 2005 05:25 pm |
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Brockbat ,
It would probably work best to construct a double roof in bat house and put sand or coarse gravel between the 2 roofs.
If you are making a five chamber bat house and it is 2ft wide and 20" long. Make the bat house 26" or 28" long.
The baffles would probably be 18" deep - measure up from the bottom of bat house 18" and mark. Next use a piece of 2 by lumber for inner roof and cut so it fits inside the bat house.
When you put bat house together fill space between inner roof and the outside top roof with sand or gravel.
Use a 1" piece of lumber for outer top roof and paint it black , use 3/4" or 1" for baffles instead of plywood. You have more control of the internal temps in bat houses using 2" and 1" lumber instead of plywood.
When it is cool bats tend to hang at the top of bat houses , this is when then sand or gravel plus 2" inner roof helps keep temps higher ,if temps rise bats move toward bootom of the houses.
Kent Borcherding
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brockbat
Member
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Posted: Sat Jun 11th, 2005 02:21 am |
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Hey Kent:
Thanks for the info on the sand in the roof. I wont loose any roost space that way. I've been using 1/2 inch plywood for my bat houses but I just came across alot of 12"x1"x10' white oak boards that have been in my inlaws barn for decades. I'm sure if I build a multi chamber house with a sand filled roof it would retaine heat for many hours after the sun sets. It would wiegh 100 lbs or more but should last a 100 yrs.
I'm thinking the sand chamber should be well sealed to prevent bugs and moisture from getting in and stop the sand from leaking out over time. Or better yet fill the roof chamber with concrete. I'll have to work on some plans for that and maybe we'll get a few more replies on this subject before I buld it sometime this summer.
Thanks, Brockbat.
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