My apologies to the very few out there who love starlings, but they are famous lice carriers and also are mean to other wild birds. They could also be carrying some other diseases, but H5N1, at least in this part of the U.S., is rarely spread by a songbird, not that I'd call them one. It's mostly waterfowl.
I'd use something like
@Al Gerhart suggested lime, or a faster substance but more expensive would be permethrin dust; then after a couple of hours, I'd spray Odoban or some other virus/disease/bacteria killer all over, let it dry for an hour or two and it's safe for chickens then.