They are going to have to adjust. Ducks are like us old men. We do not like change. I feed both cut up water melon for treats and on the Rhine when I want to keep them busy. They were disappointed when I gave them cut watermelon yesterday as they are used to peas and mealworms when they see me...
They have to get used to it sooner or later. When we get our new place in a few weeks, I am not going to let ours out of their coop for the first day or so.