The breeding range extends from the British Isles and France westward into central Asia and China. They winter from Spain and the Mediterranean west to southern China and Japan.
Prefered habitats tend to be brackish waters, but are also seen on inland lakes and rivers.
They are still very common in the wild, and have been popular aviary subjects for many years. Drakes of this species don a characteristic knob at the base of their bright red bills. They are also much larger than hens. However, the overall coloration is about the same in both sexes, with the male being brighter. Immatures resemble adults, but are paler and have a white ring around the eye.