They won't eat them here unless everything is frozen either. It's key to the pattern. I'm convinced it's their avenue of last resort when they can't dabble because all the shallow water is frozen. Once they start keeping a hole open out in the middle of larger reservoirs, it's time to start looking for it. Usually, it's something that happens when everyone else thinks you need to be on the river or creek. That's when I start looking for ducks using corn fields. You also probably won't see them unless you are there at 4 pm til dark. They will sit and conserve energy all day then fly for the last hour of light gorging as much in calories as possible, often flying back and forth to their roost for water. You'll here a lot of "it's all froze up, all the ducks already flew south". I'm telling you from first hand experience, they don't fly South unless their food gets covered in snow. As long as they can find grain in an ag field, they will find water or keep it open. This is primarily mallards though. There are a few other ducks that will stay with them, but it's 99% mallards. An old duck hunting buddy used to always say, "ice brings mallards" it's always proved true to me.