I thought maybe squirrels, too. I wish I could more accurately describe the sound, though. There was a rustling, kinda like wings, which made me think it might be a birds nest. But there was also a scuffling and something like a squeaking noise but not really squeaking. I know, I sound like an idiot. I can get into the attic from the inside of my house and I have a guy coming, actually, to look and see how much more insulation I need so this will work perfectly. He won't be here til next week, though, because I'm having a new stairway installed as we speak. Yeppers, my son is home visiting because he's headlining at a club nearby, it's the holidays and I'm having construction done and I've got critters running around, hopefully not bats in my belfry. (Although my son would probably argue that point. ) Good timing on my part, eh?