Ducks are mostly aquatic birds, generally smaller than the swans and geese, and may be found in both freshwater and seawater. Predators of the adult duck can be large fish, alligators, crocodiles, and predatory birds such as the Peregrine Falcon. The best thing you can do to get rid of ducks is to block access to any food or water. If this is not possible, you have to try your best to scare them away using sounds, decoys, and other repellents. Some online sources recommend stringing ropes or string around your property to keep them out. Do not do this as ducks can become easily tangled in them. Remember that ducks are protected under the Migratory Bird Act, so it's illegal to shoot at them or near them.