Ski, I have built both bat houses and bluebird houses.
So far, I have never had a bat take up residence.
However, I did successfully get blue birds to nest. I was thrilled. Then, the squirrels successfully wrecked the nests and got the eggs. I tried building excluders but I couldn't get them tight enough around the T posts. So, I kinda bent it down and hung it like a pup tent so the tree rats couldn't get above it. That worked. However, they flap in the wind and now not even a self respecting sparrow will use them. I hope your luck (or skill) is better than mine.
