I built an overhang on either side of my tobacco barn. Great because it fortifies the old barn and gives storage space for mowers, etc.
About a year ago I had a bird building a nest so I fabricated aluminum flashing pieces over every post at 45° angle, then cleaned all the mud, horsehair and bird crap off everything.
Next day it was back at it. This time I put up pie pans, colored beads, spinners, etc. wasting $30-$40. Didn't phase it, back again.
It's like this thing had OCD! I then bought nice birdhouses installed near where it was trying to build nests. I'd wash that area and it would simply move a foot over.
I said screw it...got my BB rifle and target sited it in perfectly. Bird came back and "plink" it was over.
Now I may be hated or burn in hades but for weeks gave it every chance in the world and since then not a single bird has been back to those overhangs.
I have bird feeders, water and over 30 birdhouses so for that one bird I killed I'm sure over the years over 100 have replaced it.
Ground hogs tunneling under buildings, mice and rats, opossums in horse pasture (Opossums can transmit Equine Protozoal Myeloencephalitis EPM) I'll either trap or shoot. When an animal causes problems it has to go one way or the other, I'm not living with a nuisance.