Wild ducks can be fed raw corn kernels, birdseed, vegetable scraps, mealworms and shredded lettuce. Although bread is often used to feed wild ducks, it can actually contaminate duck ponds and causes malnutrition, deformities and aggressive behavior.
Healthy duck treats mimic the sort of diet they would have without any human intervention. Wild ducks naturally feed on a mix of insects and plant material. Foods such as lettuce shreds and raw grain are very similar to the foods wild ducks encounter as a part of their daily foraging. Worms are also healthy for wild ducks and can serve as treats, although they are relatively rich in protein and can cause problems if overfed.
Ducks rarely encounter anything as carbohydrate-rich as bread in the wild. When fed large amounts of carbohydrates or protein, wild ducks can develop a disabling condition called angel wing that prevents them from flying. Ducks can also become aggressive towards humans if overfed bread, and wasted bread can cause mold outbreaks in duck ponds.