There are two different categories for bats listed by the State of Vermont, one is cave dwelling and the other is migratory bats. The migratory bats will "fly south for the winter" to the warmer climate and during the warm months in Vermont, they will roost in trees. The cave-dwelling bats are the type to invade structures, usually the attic spaces. There are six species of bats in the State of Vermont. They are Big Brown Bat, Little Brown Bat (state endangered), Northern long-eared bat (state endangered), Tri-colored Bat (state endangered), Eastern small-footed bat(state threatened), and the Indiana Bat which is federally endangered.
Quite frankly, it doesn't really matter what type of bat has invaded your structure, it is best to assume it is endangered and excluding them out is the only option. NO HARM WILL COME TO ANY BATS. Each structure is looked at individually and an exclusion plan is developed. The exclusion process will usually occur between August to November.