Climate change and crowds tough on harlequins

Warren Hansen, a graduate of Polson High School, has channeled his lifelong love of ducks and the outdoors into a long-term examination of harlequin ducks in Glacier National Park’s McDonald Creek watershed — a renowned hot spot for harlequin breeding activity.

With their signature plumage rivaled only by the beauty of their migratory mountain homes, harlequin ducks have captured the hearts of countless bird watchers and casual observers. The rare birds are sea ducks that typically spend their winters residing in coastal surf zones before migrating inland to nest alongside whitewater mountain streams.

“They’re the only bird to have an east-west migration,” he said.

Hansen has made harlequins the focal point of his life for the past three years and the subject for his wildlife biology master’s thesis at the University of Montana.

The harlequins found an ideal habitat in McDonald Creek and its pristine tributaries. The 10-mile stretch of the stream hosts about 20-40 breeding pairs — about a quarter of Montana’s population.

“McDonald Creek has the highest breeding density of harlequins in the Lower 48,” Hansen said.

While their relative abundance may suggest that the Park’s harlequins are thriving, Hansen’s thesis examines their vulnerability to stream flow variation and human disturbances. He’s gone to great lengths to study harlequin nesting sites, occasionally scaling cliffs or finding himself surrounded by grizzly bears in the process.

Hansen has found the harlequins are up against some significant challenges. With to their reliance on synchronizing migration with peak mountain stream runoff, the greater unpredictability of stream flow due to climate change makes harlequins vulnerable.

He’s found evidence to suggest “nests may be getting flooded out by these fluctuating stream flow levels,” reinforcing speculation that changing patterns in temperature, snowpack and precipitation may “significantly impact the success rate of reproduction of harlequins.”

Human disturbances have also impacted the ducks. With millions of visitors crowding into the Park each summer, harlequins are often shunted away from perfect habitat, Hansen said.

“Maybe the ducks are able to find ideal habitat elsewhere, but maybe not,” he said. “Maybe they’re displaced into poorer quality stream reaches.”

Despite these challenges, Hansen is “generally optimistic” harlequins demonstrate enough natural variation and resilience to persevere in the face of uncertainty, especially if conservation efforts are continued into the future.

“They are very much in the public eye, and I think that the public’s best interest is whatever will help these ducks continue to persist into the future,” he said.