Several years ago we noticed bat houses at the zoo. My husband found a pattern for them and built one and put it on the garage. Further research said it could take 4 or 5 years to actually attract bats. I think it's probably been 7 and I had given up. But I noticed droppings this week and upon further investigation it looks like we have three! I'm guessing that losing a big part of the tree that is between the house and the garage is the reason we finally have bats. I imagine the tree was simply in the way. Too cool!