How can I tell if there are ducks coming to our crawfish ponds?

We have 70 acres of crawfish ponds ( 4 total). There is a treeline running on the backside of it, with a creek running through the middle with trees covering the creek. It is located in Breaux Bridge, LA, so I am pretty sure it is in the flyway... how can I be sure that ducks are frequenting the area? Any help would be appreciated as I am new to duck hunting after being a deer hunter all my life.