I also have a couple of permissions at Dairy farms. Unlike your experience I had to resort to a shotgun and get the pigeons as they flew out of a shed where they roost. Really spooky for some reason. The pigeon poo was shin deep right under their roosting spot.
However my permission is just like yours with the Starlings. Right now there are three sheds with Starlings roosting everywhere. There are like white chalk lines of feces below all the rafters. I too will use night vision but I have seen some of the videos where the shooter was using just a red LED. It didn't seem to spook the birds but green did. I thought I saw that white was even better than green. I can easily mount the LED light on the barrel and use the regular scope which would make it much easier and lighter. However, don't know if the red LED will spook them. It's too darn cold out there now so it might be awhile before I go test the red LED. Any info about the red LED come your way?
The 12 FPE and not putting holes in the roof will allow you to keep the permission longer. I have heard good things about the new JSb Hades. Might be better than the wadcutter. Maybe you should give them a try.