I had my husband dismantle the fire surround once because I heard scratching, he found a bird that had fallen down the chimney.
That's one thing I'd never want to live with, I hate anything with a tail.I have exactly the same problem, it's almost certainly going to be mice. I suggest getting the plastic traps and using peanut butter as bait, we catch at least one a week. We've had the council & a pest control company out and they say it's inevitable in the countryside and something we need to live with!
Go up there and stay for a while so as to look carefully for bird or rodent signs. Remember that this is man against nature. Can you set a trap? Can you call an exterminator? He has had much experience with this sort of thing and can figure it out, find where the bird or rodent is entering, etc. Or if there is no other evidence of bird or rodent egress and they're not in the house, (just in the loft) just live with it.We keep hearing scratching noises in the loft but whenever I go up there's no signs of birds or rodents. Because I read The Exorcist years ago and the first signs of something happening is sounds in the attic it freaks me out every time I go up in our loft!
Tiny things with tails, I like cats but I'm afraid of dogs. My granddaughter wanted a hamster so we went to the pet shop and they gave us a chose between 2 varieties, we asked what the difference was and she said one has a tail and the other doesn't I screamed " no tail!! NO TAILl!!! "Dogs & Cats too?