Juveniles are grayish-brown with small indistinct cheek patches. Buffleheads are agile swimmers and divers but awkward on land because their legs are set well back on their bodies. In flight they are one of the fastest of all the waterfowl, and can be recognized by their small size and rapid wing-beat. They are relatively quiet ducks. Males during courtship emit a variety of sounds described as squeaks, chatters, growls, and guttural rolls.
Females also employ a loud guttural call during courtship and nest site searches.
Hens with broods use soft contact calls to keep the ducklings together and a louder alarm call when danger threatens. The common name Bufflehead is a corruption of the original name Buffalo Head, a reference to the disproportionately large domed head of the drake. The vast majority of the population breeds in a wide band of boreal forests and aspen parkland stretching from Alaska to Manitoba. Smaller, isolated populations breed in Ontario, Washington, Oregon, California, Idaho, Montana, and Wyoming. There are sporadic reports of birds breeding in Quebec, Vermont, Massachusetts, Minnesota, South Dakota, and Colorado.