They can eat leafy greens, small fish, and low-sugar fruits. The fruit and fish are minimized because store-bought fish are normally extremely fatty, and too much sugar can cause liver problems. Bread crumbs are never a good idea, but can be used as a treat every month or so. You will need a LOT (and I mean a TON) of time for ducklings as they have to be fed every 2 hours or be able to access fresh food or water constantly and have food taken away at night and given back at morning to prevent obesity and eating disorders. Good luck!