Baby ducks and geese should receive care from a licensed wildlife rehabilitator. Wildlife rehabilitators are trained to provide care for wild animals. They are licensed to do so by provincial and/or federal governments.
Baby ducks and geese need a specialized diet, species-specific housing, and medical treatment that you cannot provide at home. They also have to be raised with other baby ducks and geese to learn the social behaviours they need to survive in the wild. It is illegal to keep any wild animal at home without a permit for longer than 48 hours. Please contact a wildlife rehabilitator right away for help with the duckling or gosling you have found.