- Natural or genetic causes: Some duck species, such as the flightless steamer duck and the Auckland Island teal, have evolved not to fly. These species have adapted to living in environments where they do not need to migrate or fly long distances to find food.
- Injuries: Ducks that have suffered wing injuries or other physical injuries may not be able to fly.
- Captivity: Ducks that are kept in captivity, such as in zoos or parks, may not need to fly and may lose the ability to do so over time.
- Domestication: Some breeds of domesticated ducks, such as Pekin ducks and Muscovy ducks, have been bred to be heavier and less mobile, which can affect their ability to fly.