Thanks for posting that link. It appears the bats I think we have - little brown bats (seriously) - will roost in caves, as well as trees and structures. I would think the caves likely to have a moderated temperature relative to the black painted bat boxes I've built so perhaps temperature is not the deciding variable.

Thanks again!

Bats in several places are extremely threatened -- look up so-called "white nose disease". It has wiped out 90%+ of many large colonies here in the northeast and in New York and other places, too. They are not hibernating, and they are starving to death and they have this white fungus/mold growing on their noses. In some cases, whole caves are losing virtually all their bats.

This fungus (Geomyces destructans) was recently introduced from the Old World and kills bats by invading the bat's body while they are in hibernation and their slowed metabolism is unable to resist its spread. Old world bats are resistant to it, but not New World bats. It is mainly killing out the colonial cave dwelling bat species and likely to continue spreading across temperate North America killing most of these bats. Hopefully a few individuals will prove to have some resistance to the fungus and can repopulate after all of the susceptible individuals have been killed, which is likely what happened in Eurasia when this fungus first made the jump to bats over there. Non-hibernating bats (tropical species and the few temperate species that migrate south for the winter) are unlikely to be affected by this fungus and the solitary habits of the non-colonial hibernators hopefully will allow them to avoid the worst effects of this fungus.

It will be interesting to see what effect this bat die out will have on the populations of the bat's main competition (wippoorwills and nighthawks) for the night sky. Since these birds lack echo-location and hunt by sight, they are limited to hunting insects at dust, dawn, and when the moon is up. They even time their egg's hatching so the hatchlings greatest food demand will be during a full moon. An inadvertent effect of the spread of light pollution is that it has benefited these birds by allowing them to hunt all night on moonless nights.

The site I found about bats is online again:) Here is it is:
Skrzynki dla nietoperzy and its Google translation.
It is about bats in Poland, but much of the info is common for other species.
In case it goes offline again, here are the three bat house plans it links to (dimensions are in millimeters):
http://ecorenovator.org/forum/attach...1&d=1339752181

http://ecorenovator.org/forum/attach...1&d=1339752181

http://ecorenovator.org/forum/attach...1&d=1339753095

Thanks for that. The dimensions are drastically different than what I've done having much more spacious chambers. This winter will see me building another bat house to be tried in a different spot. Perhaps a design change is in order.

Thanks again!

More spacious doesn't have to mean worse: I bet that some bat species prefer to stay with their colony, while others look for a smaller summer residence just for their family. And yes, the more different places in which you put bat houses, the greater the chances of them finding an occupant. Just remember to use only nails and untreated wood; no glue, paint or other chemicals, as bats don't seem to like the smell (I can't say I blame them).

Maybe making a nice marsh with tons of mosquitoes would also lure them;) :p

One of the many things I haven't been able to find out is whether bats come back to the same feeding grounds each summer, and more specifically whether they remember where they nested last year.

We've got the pond/marsh so there's a food source. As far as coming back to the same place I'm certain they do. I've spoken to someone who is familiar with our property and he remembers the bats being here well over a decade ago and occupying the same roost. I'd bet the bats living here now were born here (and their parents too). We want to provide more and better places for them to live and thrive here as they're losing habitat all around us.

bat resources
 

My friend is actually a bat expert...

here's a resource for you guys - guidelines and all -very reputable source -

I'm too new for the system to let me post links which makes sense - so I suggest you google http://batcon.org/index.php/get-invo...bat-house.html

(Bat Conservation International is the very reputable source if you prefer not to use the link).

Love this forum. kathy

Great link Kathy, thanks!

What a timely post! I just made one myself about a month ago to hopefully get rid of some of my mosquitos. So far, no bats though. I have seen bats in my yard before, so I remain hopeful. I followed plans from the Missouri Department of Conservation. It was a pretty simple build, although I did modify the plans a bit. Here's the plans. Apparently a bat roost this size will hold somewhere around 80 bats.

http://i48.tinypic.com/2ibyel2.jpg

The bat symbol was a nice touch (just in case the bats got confused as to who it is for). My worry is that wasps will move in before the bats.

In my research, I learned a few things, some of which has already been mentioned.

1. It is very important to have the bat roost south facing. If it doesn't get enough sun, the bats won't be warm enough and won't stick around.
2. It is good if you have a large body of water within 1/2 mile of your house to serve as feeding grounds.
3. Apparently it could take up to a year or two for bats to find your roost and move in. So, I wouldn't get discouraged by not having any bats quite yet.
4. Trees are not ideal to put the bat house. They may not get enough sun and they leave the bats exposed to predators. They also should be at least 12 feet above the ground. I hung mine on my chimney.

That's all I can think of for now. Let me know if you have any questions. Good luck!