- Bald eagles: Bald eagles are large raptors that prey on a variety of birds, including harlequin ducks. They typically hunt by soaring over bodies of water and then diving down to catch their prey.
- Golden eagles: Golden eagles are another large raptor that preys on harlequin ducks. They are similar to bald eagles in their hunting behavior, but they typically live in more mountainous areas.
- Great horned owls: Great horned owls are large owls that prey on a variety of animals, including harlequin ducks. They typically hunt at night, and they use their sharp talons to kill their prey.
- Red foxes: Red foxes are predators of harlequin ducks, especially during the nesting season. They typically steal eggs and young ducks from nests.
- Marten: Marten are predators of harlequin ducks, especially during the nesting season. They typically steal eggs and young ducks from nests.
- Fisher: Fisher are predators of harlequin ducks, especially during the nesting season. They typically steal eggs and young ducks from nests.