Little Brown Bats! My personal favorites (prolly because of personal experience).

Bats don't intentionally fly into a house's living space -- in my case, they accidently slip through around the chimney (or, in the case of the baby, through the 1 or 1-1/2 inch gap in the sheetrock at the ceiling's peak and around the 2x6 trim piece). Even if I don't help them, they usually find their way out again.

Alas, my nursery colony seems to have abandoned us -- the flying squirrels and the bats loathed each other and seem to have chased each other out to seek other habitation. (And I guess that's good...) But I truly enjoy having Little Brown Bats in the vicinity. Before they moved into our roof, they, uh, "hung out" under the sumac that then infested my "back yard".

Linn