Well then my non expert opinion is "don't sweat it!"
We bought this place at the end of 2011, prior owners apparently owned (over time) just about any animal you might find on a farm but bovines. There are 2 pre Civil War barns (not in good shape) and the lower part of the small one has been set up for fowl, but it is foul (bad roof). And it is not at all predator safe (gee I wonder why he lost chickens to weasels when you can see light between the foundation rocks). So I converted a horse stall (*) in the lower part of the big barn to a predator safe coop. There is a pond in a (poorly fenced) barnyard behind the barns. We get a couple of migrating Canada Geese and Mallards coming through in the spring. They hang about for a couple of days.
The chickens have free run of the lower part of the barn all day, the "barnyard" any time we are gone for just a few hours and anywhere they want to go (they self limit to about 100' from buildings) if we are home. There is no way to keep them from going where wild birds have been including inside the barn, they seem to prefer the layer feed to whatever they would eat outside while my chickens love to forage"real" food. I've not seen any disease or parasite problems in my birds. If the avian flu starts showing up in the Eastern migration corridor, I will have to take steps to keep them from visiting us.
Of course, your "mileage" may vary

and I can certainly understand not wanting to take any chances with special birds!
* There was a lady that boarded 3 horses here when we bought it and her horses were here until about a month before I got chickens so the chicks were on "pasture" that had recently been used daily by horses for quite some time.