- 13–21.3 in
- 22–26 in
- 17.6–25.6 oz
- Arlequin plongeur, Canard arlequin, Canne de roche (French)
- More than half of eastern North American population of Harlequin Ducks winters in coastal Maine, particularly outer reaches of Penobscot and Jericho bays.
- When engaged in behavioral interactions, the Harlequin Duck gives distinctly unducklike squeaks, the source of one of its local names: sea mouse.
- The oldest recorded Harlequin Duck was a male, and at least 20 years, 9 months old when he was seen in the wild in British Columbia in 2014 and identified by his band. He had been banded in Alberta in 1995.
Mountain streams and rivers, usually in forested regions; in winter, primarily turbulent coastal waters, especially in rocky regions.
Insects, fish, and marine invertebrates.
- Clutch Size
- 3–9 eggs
- Egg Description
- Pale creamy to pale buff.
- Condition at Hatching
- Covered in down and able to leave the nest soon after hatching.
Dives for prey on or near bottom.
There is little information on Harlequin Duck population numbers and trends, but wintering populations in eastern North America are currently much smaller than historical (late 1800s) numbers. However, populations grew in the last part of 20th century. The species rates an 11 out of 20 on the Continental Concern Score. Harlequin Duck is not on the 2016 State of North America's Birds Watch List. The species is listed as endangered in Canada, threatened in Maine, and a species of special concern in western states.