Don't know what they call it but I see that reflective (Mylar?) tape in a lot of orchards. Keeps the crows and other birds out. Maybe put it on poles out in your marsh? Are you trying to keep birds from working the areas you aren't hunting? That can sure be frustrating. If you just want to keep them out use a Zon gun.
Thanks - The reason is I have a large area to hunt, and one 80 acre field in particular is difficult, as you can walk into one side, flush hundreds of birds, they just get up and land 400 yards away and suck in every other bird that flies by. I'll try something...
Maybe this is a crazy one, but cheap if it doesnt work. Try some of the little silver windmills that kids play with. They will move quite a bit in a small breeze and the shine will be similar to mylar. Like I said, it may not work but those things are a dime a dozen.
If that doesnt work, invite some friends who cant shoot straight to hunt the other side of your field. THAT will keep 'em moving.
Just tape a typical morning on most refuges when most hunters are screaming hi-balls on their etched and gold laminated calls and you should have nothing to worry about. Throw in twelve booms from a sound cannon every few minutes and that should seal the deal.