The bizarre life of the harlequin duck

National Wildlife, Dec-Jan, 1996 by Gary Turbak

Biologists are still baffled by a duck that would rather swim than fly and that migrates east and west instead of north and south

A gentle splash on the water's surface punctuates the landing of a harlequin duck on a secluded mountain stream. Moments later, her mate touches down. They have traveled far to reach this spot, along the way perplexing a cadre of biologists eager to unravel the enigmas surrounding this most mysterious of American waterfowl.

Harlequins are sea ducks that live in the mountains. They migrate east and west instead of north and south like other ducks. And they prefer roaring alpine streams to the quiet marshes favored by other waterfowl. "I can't imagine why this bizarre lifestyle might have evolved," says Greg Schirato, a wildlife biologist with the Washington Department of Fish and Wildlife. "It just doesn't make any sense."

Schirato and other scientists are working hard, however, to solve the harlequin mysteries. Recent research has revealed that these birds reproduce slowly, are vulnerable to oil spills and become quite attached to certain streams--and to each other. Banding studies have documented the ducks' extensive travels--some harlequins winter along the British Columbia coast and nest in the Rocky Mountains. "But lots of pieces to the harlequin puzzle are still missing," says Frances Cassirer, wildlife biologist with the Idaho Department of Fish and Game.

As biologists learn more about harlequins, concern about the bird grows. While many of North America's 35 duck species prosper, harlequin numbers appear to be declining. In 1990, Canada's Committee on the Status of Endangered Wildlife designated the harlequin as endangered in eastern Canada, and in 1991 the species became a candidate for U.S. listing. Only one North American duck, the spectacled eider, is probably more imperiled than the harlequin.

This continent is home to two widely separated harlequin populations. A small eastern contingent breeds in maritime Canada and winters on the New England coast. The more numerous Pacific harlequins winter along coastlines from the Aleutians south to California and breed in western mountain ranges as far inland as Wyoming. Additional harlequin populations also exist in Greenland and Iceland.

"Judging from their current distribution and the much larger population in the North Pacific, it's possible that harlequins evolved in the West and have been slowly colonizing eastward," says Pete Clarkson, a park warden working with harlequins in Canada's Jasper National Park. This hypothesis suggests that huge gaps subsequently developed in the bird's distribution, creating the now isolated groups. Puzzled by the disjunct distribution, researchers have begun studying harlequin DNA to see how closely the different populations are related.

East Coast harlequin numbers have declined from perhaps 10,000 birds in the 1800s to fewer than 1,000 currently. "This population is doing terribly and may be headed for oblivion," says Jim Reichel, a zoologist with the Montana Natural Heritage Program. Before its prohibition in 1989, sport hunting was probably the main mortality factor for eastern harlequins. Now, oil spills and dams are the primary problems.

Early, unreliable estimates for the Pacific population went as high as a million birds. Today, biologists guess there may be about 250,000. "The little data we have," says Reichel, "suggest that western harlequin numbers have declined over the last 40 or 50 years." Habitat loss, oil spills and disturbance of nesting ducks by humans are thought to be the principal culprits.

The decline has researchers scrambling to get a better fix on the bird's status--and its unusual lifestyle. Every spring and summer, researchers band harlequins to identify migration routes and habitat preferences. In addition, biologists monitor streams to plot harlequin distribution and to gauge the species' tolerance for disturbance. Researchers also attach radio transmitters to hens to locate nests.

Weighing only a pound and a half, a harlequin is barely half the size of a wild mallard. The hen is cloaked in subdued browns, but the drake's splashy colors--seemingly assembled by a committee of first graders--are among the showiest in the waterfowl world.

Although classified as sea ducks, these avian mariners weigh anchor each spring and migrate inland to breed. The Pacific birds wend their way to rushing, tumbling mountain streams, while the eastern birds settle on turbulent rivers primarily in Quebec and Labrador but occasionally in Newfoundland. The Pacific harlequin is the only duck in the world that divides its time between sea and mountains.

In spring, breeding-age western harlequins--those two years and older--leave Pacific coastal waters for mountain streams in Alaska, Washington, Oregon, Montana, Idaho, Wyoming, Alberta, British Columbia, the Yukon and the Northwest Territories. A few even cross the Continental Divide to nest. Researchers believe some harlequins journey from sea to summit as anadromous fish do--by following streams.