I am renovating an old stone/timber cottage. Small bees keep appearing inside, and they must be falling down the chimney and then can't find a way back so either die or get rescued by me. I have shone a light all the way up the chimney but there is no sign of a nest or even any bees. The bees seem very passive with no sign of a sting, and they make no wing noise when flying. I have attached a picture.