Merginae

The Merginae or seaducks are a subfamily of the Anatidae, the duck, goose and swan family of birds.

Sea Ducks
Histrionicus histrionicus drake Barnegat.jpg
Harlequin Duck, Histrionicus histrionicus (male)
Scientific classification
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Merginae

As the name suggests, most are marine outside the breeding season. Many species have specialized salt glands to allow them to tolerate salt water, but these have not yet developed in young birds. Some species prefer riverine habitats.