I had rats get into my porch and attic and they climb anything! Try getting a sticky glue trap and putting it up where your chain is hanging from. I hated having to deal with the living rat stuck on the sheet, but after months of trying cayene pepper, oiling everything they climbed up, plugging up all the holes they'd found and made, and snap traps, the sticky traps are what finally solved the problem.
Other than that, I'd recommend getting a IR camera and recorder. You can find a small system for pretty cheap these days and it could pay for itself in the long run in what you save in lost feed and losses to your flock. It does help to know what you are dealing with!
You might also want to consider enclosing the top of your run. I know fencing is pricey, but you could try something like weed block fabric. Or Big Lots has tarps for pretty cheap that you could just staple on, but add a center bar to the structure that is a bit higher so rain runs off like a peaked roof.
Good luck!
I'm not a rooster, but I reserve the right to crow! 1 husband who wants a rooster and will not get it, one son who flew the coop, one lovely german shepherd, one amazing adopted farm dog, three gold sex links, two who hit 17 weeks old the first week of July and laid first eggs 7-15-12!!
I'm not a rooster, but I reserve the right to crow! 1 husband who wants a rooster and will not get it, one son who flew the coop, one lovely german shepherd, one amazing adopted farm dog, three gold sex links, two who hit 17 weeks old the first week of July and laid first eggs 7-15-12!!