Let me first disclose that I know nothing about duck hunting. However, a business contact who was an avid duck hunter once said that he would pour molasses in his duck ponds. Apparently the ducks would fly home with the smell of the molasses on them which would in-turn, cause more ducks to follow them back the next year. Sounds simple, and could even be deemed illegal or even unethical according to one's personal opinion. Just sharing what he told me.