Harlequin ducks ride the surf off Beavertail Park in Jamestown. At top, URI grad student Christine Caron uses a spotting scope near Beavertail Lighthouse while looking for ducks.

The Providence Journal / Bob Breidenbach

JAMESTOWN

They float on the rolling surf with the greatest of ease in groups of five, two and three.

The harlequin ducks stand out from other waterfowl with their distinctive white markings. True to their namesake — the motley clown — the adult males dazzle with plumes of light chestnut and iridescent dark blue. The females are a subdued brown.

One minute these winter visitors bob on the frigid water. The next, they disappear beneath the waves for food. The rocky coast provides a smorgasbord of amphipods and other small creatures, including mussels and snails.

Christine Caron, a bird watcher and University of Rhode Island graduate student researching the ducks, witnessed this scene many times over the last two years, during mild days and rough 40-mph winds.

“I kind of like waiting for them,” she said. “They do diving a lot and I feel like they’re playing hide and seek. You see a couple and then you’ll see none of them. … They’ll pop up.”

These birds, relatively rare on the East Coast, are vacationing on Rhode Island shores in steadily increasing numbers, about 3 percent more each year since 1975, according to Carron’s study. Her paper examines data from the Audubon Society of Rhode Island’s annual Christmas Bird Count since 1975 and U.S. Fish and Wildlife surveys going back to 1984 and 1992.

Last winter, Caron counted 150 harlequins during weekly observations at Sachuest Point National Wildlife Refuge, in Middletown, and Beavertail State Park, in Jamestown.

This winter, she estimated there might be more — good news for a small population of 1,800 to 2,000 on the East Coast.

Harlequin ducks are a charismatic species mostly known for their beautiful color, said Rick McKinney, a research ecologist for the U.S. Environmental Protection Agency’s Atlantic Ecology Division.

The eastern ducks breed during the spring and summer along rivers and streams as far north as Quebec, Labrador and Newfoundland, Canada, and Greenland. An estimated 1,150 to 1,300 ducks winter along the Maine coast, Caron said. The rest dot the seaboard in small groups, gradually thinning out south of New England, McKinney said.

Out West, the harlequin population is more abundant, with 200,000 to 300,000 ducks from Alaska and Canada to Oregon, McKinney said.

Historically, the eastern harlequin duck population dropped from a peak of 5,000 to 10,000 in the 1800s to fewer than 1,000 in the 1980s, according to Caron’s paper. A number of factors contributed to the decline, including habitat loss, oil contamination and hunting.

Caron attributed the latest resurgence to less hunting and stricter environmental laws. In Canada, the birds were listed as an endangered species from 1990 to 2001. They are currently listed as a species of special concern. In Maine, where Caron hails from, the ducks are considered threatened.

In Rhode Island, the duck counts grew from below 40 in the 1970s and early 1980s to more than 100 in the late 1990s, according to the Audubon Society’s Christmas Bird Count.

The main stronghold for harlequin ducks is Sachuest Point. Many visitors from across the state, Connecticut and Massachusetts stop by to see harlequins and other waterfowl from observation platforms, said Suzanne Paton, a wildlife biologist for the Rhode Island National Wildlife Refuge Complex of the U.S. Fish and Wildlife Service.

“It’s more something you can count on,” Paton said. “Winter means you can go to the shoreline and see sea ducks you don’t see other times of the year.”

While most harlequin ducks still congregate in Middletown, a clique of more than 20 birds has been appearing in Beavertail State Park since 2000, Caron said. And a small group migrated to Sakonnet Point in Little Compton.

One theory Caron has for the duck drift is crowding at Sachuest Point. Another possibility could be mating. Mated ducks reunite at the winter grounds and they tend to return to the same place year after year, Caron said. A few males and females and their offspring might be contributing to the small exodus.

Caron’s research has been very useful in understanding the local population, Paton said. The next step would be to combine that information with data from Maine and look at trends on a larger scale.

Bird watchers who want to catch a glimpse of these fancy feathered fowl this season had better move fast. They usually begin their northern migration in late March and early April, depending on the weather, Caron said. The colder it is, the longer they will stay.

To learn more about harlequin ducks, visit the Sea Duck Joint Venture fact sheet at www.seaduckjv.org/infoseries/hard_sppfactsheet.pdf

Michelle J. Lee is a fellow with the Metcalf Institute for Marine and Environmental Reporting.

mlee@projo.com