I have some experience with this in downtown chicago on a hi rise and another mid rise.
We tried the speakers that make the sounds, worked for only a couple days then the flying rats get used to the sounds and come back.
We tried the owls, the wind flapping bright things that are supposed to scare these flying pos. these didnt work.
We consulted professional pigeon hunters (relocators) and they would have worked but downtown chgo was not a good environment for the tactics these guys use (large nets fired out of guns, traps, etc.)
What worked was the bird-x gel that you apply using a caulk gun. You zigzag the gel (follow the directions) and that was a permanent solution.
At another building, also downtown chgo, there was a large conduit (4" or so) that the pos loved to sit on and poop. Because of the smaller surface area of the pipe, a single piece of rope strung from one end to the other and tied off worked great and was the cheapest.
good luck.