Bats in the Belfry

Well not really a belfry, but we do have this crazy canopy on the deck (off our bedroom) that we bought to sleep in when the nights got too hot this summer. We haven't slept out there yet, but we have found some froggies and other critters camping out there. Mostly the critters were a mild surprise, not entirely unexpected. The typical find was insects and lizards that criss-cross the deck a zillion times a day. But twice now, quite surprisingly, a bat found its way in there at sunset. Not sure how, because the canopy is closed at the top and only weirdly open at the bottom, which we fold up and tuck inside to try and create a boundary. How and why do the bats come in? We are not sure. We have managed to release them both times. They are truly the weirdest mammals we know, well except for modern humans who really do seem to have bats in their belfry.