Prefer to nest inland along fresh water streams with fast rapids. Have the ability to dive in rapids, collect small crustaceans, and come up in same place. Siltation of streams due to erosion from logging has diminished ability to forage. In Wyoming river recreation has decreased harlequin production. Winter in coastal bays in E Canada and Canadian pacific.
Drakes leave for wintering areas as soon as hen starts incubation.
Continued subsistance hunting threatens the remaining populations. In winter eat herring roe. Oil spills have also damaged pacific feeding areas. See Nat Geog. The Old Squaw is the trimmest of sea ducks.