They eat things like small crabs and mussels. In the spring, they leave the salt water and move inland to fast-flowing freshwater rivers and streams with rocky shores and ledges. This is where they make their nests and lay their eggs. They feed by diving and digging into the bottom of the stream for insect larvae and aquatic insects. In early summer, they build their nests, often on the ground.
Females seem to choose the same sites year after year.
The females lay between three and eight eggs, and then incubate them. This means they sit on the eggs, keeping them warm, and leave only to eat. When incubation begins, the male ducks leave. Ducklings begin learning to swim and catch food within a day of hatching. They are able to fly at about 1 to 2 months of age.