Awwww. Well I'd try the furthest place with fresh water and they know how to fly. It's definitely difficult knowing they are vulnerable although I know you wanted them to be free. Predators are everywhere so it's just the way of nature. They are just doing what they know but will become wild if...
They are so adorable..:frow
Here when rehabs release Birds, they take them far from home base so they have to fend for themselves without the possibility of them returning.
Not sure if your willing to do that though?