Bats in the Belfrey

A belfrey is the top of a tower where a bell (or bells) is (are) placed.  Such locations are most often found in older churches and city builings, and are open on all sides as to allow the bell(s) sound to be heard everywhere.  Given the openness of the space, it's not unlikely to find bats living in it--especially when the bell is not often used.  The bats are seen as an irritation, especially when one has to clean the area, and can be hazardous to anyone doing so as they fly about the head, potentially making you unballanced, and likely to fall.  The reference is also used referring to a person having an unbalanced mind, or essentially being crazy.
Quod erat demonstrandum.