Our stable doors stay open, rarely ever shut, but no birds. I see one bird and it's chased out, usually just lots of noise or water hosed spray.I've had horses for most of my life, and I have never even known anyone that keeps their barn locked up so tight that birds can't come inside. If you don't plan to keep any animals in the barn, you might be OK.
I think the biggest problem with bird crap is that people don't like to look at it. I don't care for it either, but after hauling out a trailer load of horse manure every day, it doesn't seem like that big of a deal to me.
You don't feed these ones. They feed themselves on the very same bugs you will complain about when they are gone. The bird sh^t on hay can be avoided. Look at covering small areas at a time to keep it off the hay. I will agree with the hay portion. The health hazard??? Don't eat it and don't play with it. Wash your hands. It is a very short window in the whole grand scheme of things they will be in the barn. Once the young are in flight they rarely frequent the barns. I'm not even sure they roost in barns once all in flight. I'll have to remember to keep looking. Some of mine are still nesting.Birds are fine. We feed them all winter and have 50 birdhouses everywhere, but they are nasty in a building. I wouldn't feed a horse hay with bird sh*t all over it. It's very much a health hazard also.
Our area is becoming ever more gentrified with McMansions going up all over.Some people like country living but also dont like country living. lol.