The lords and ladies of Glacier National Park live in relative obscurity, but researchers continue to shed light on harlequin ducks, a sensitive species whose vibrant plumage brightens the cold, clear waters of Upper McDonald Creek in droves every summer.
With painted faces, slate-blue bodies, accents of chestnut and bolts of white, harlequin ducks migrate from the coastal waters of Puget Sound or British Columbia each year to navigate the roiling whitewater on a 10-mile stretch of Upper McDonald Creek – a section of whitewater that holds the densest breeding population of harlequins in the lower-48 states.
But the species is sensitive to human disturbance and climate change, and in Glacier Park, where more than 25 percent of Montana’s harlequin chicks hatch, the birds are at risk, according to Lisa Bate, a wildlife biologist at Glacier National Park who led a three-year study of the ducks.
Bate launched the research project in 2011 to better understand harlequins and investigate their reproductive success and survival on Upper McDonald Creek, particularly in light of stressors like climate change and an uptick in traffic on the Going-to-the-Sun Road, which tracks along the ducks’ pristine habitat.
“Harlequins are a species of concern in Montana and elsewhere for a number of reasons,” Bate said, “but particularly because the females only return to breed at their natal streams, which means the streams where they were born.”
“So if for some reason we lose a population of ducks on a stream anywhere in the world it’s highly unlikely that it would be repopulated,” she continued. “Stream flow is supposed to be even more erratic in the next 50 years due to climate change and that does not bode well for a harlequin.”
Harlequins are vulnerable to climate change because they select nest sites close to the water’s edge – usually within a few feet of their natal streams – and depend on fast-moving water to escape predators, like wolves, pine marten and mink; however, when the streams flood, their nests are washed out. They are considered to be more strictly confined to running water than any other waterfowl species in the Northern Hemisphere.
Since the study began in 2011, researchers captured and banded 138 ducks – 42 females, 45 males and 51 chicks – and Bate said the glut of information gleaned from tracking the ducks was invaluable.
One of the more hopeful findings was that female harlequins are learning to nest away from the water’s edge, or on cliffs high above the water in order to avoid predators.
“We believe there is enough variability in nest selection that even though stream flows are going to be more erratic due to climate change, the species can sustain itself because females are nesting away from the water’s edge,” Bate said.
The study was initiated by Glacier National Park in cooperation with researchers from the University of Montana, who used radio-telemetry and banding to learn more about the location of harlequin nests and factors affecting offspring survival.
Male harlequins, or lords, are slate blue with bold white, black, and chestnut highlights. They are often referred to as “clown ducks” for their unique coloring and markings. Female harlequins, the ladies, are brown and gray which allows them to blend into their surrounding while they sit on their nests for 28 days.
Although the ducks can grow to live more than 20 years, they are naturally slow to mature and reproduce, Bate explained. Females generally don’t have their first brood until they are three years old, and only about 10 percent survive to reach the average breeding age, researchers estimate.
Their limited numbers and narrow range of habitat causes grave concern to researchers, and better information about what factors lead to nesting success could help stave off local extinction.
On the 10-mile stretch of Going-to-the-Sun Road that parallels Upper McDonald Creek, for example, vehicles trundle past the harlequins’ annual mating ground every day with the arrival of summer visitors.
The Federal Highway Administration, which oversees maintenance and rehabilitation of the Sun Road, as did the National Park Service, the University of Montana and the Cooperative Ecosystems Studies Unit. Many of the researchers involved with the project volunteered their time and expertise.
“This stretch of creek is the most productive in Montana for chicks, but it’s also adjacent to the Going-to-the-Sun Road which has 2 million visitors every year,” Bate said. “Even so, we still have this incredible breeding population, and we don’t want to see it compromised.”