Researchers releasing tested and tagged female harlequin ducks

Releasing tested and tagged females. Photo by Will Klaczynski

White Water Daredevils

By Melissa Sladek and Terry Peterson

Late summer sun shines through the car window as we drive along Upper McDonald Creek on the Going-to-the-Sun Road in Glacier National Park. Warren Hansen, a University of Montana graduate student, drives slowly, listening to a transmitter-receiver that is tracking harlequin ducks. A faint click, and then a louder and stronger “blip, blip, blip,” emanates from the device. We inch our way along the road, hoping the beeps will increase in strength; soon the receiver is silent. Warren swings the car around and drives back down the road until the radio once more comes to life. Stopping where the signal is strongest, we pull over, gather our gear, and head out on foot toward the creek, eager to catch sight of the bird responsible for the receiver’s activity.

Harlequins are small sea ducks that spend their winters along the coastal waters of North America and migrate inland in the spring to breed alongside mountain streams. These showy birds with their rounded heads and stubby bills are white water experts. In the winter, they live along rocky coasts in the midst of rough surf waters. In the summer, these charismatic ducks make their home in the frothing white water found in fast moving mountain streams. Here, they dive to forage for aquatic insects and are also able to dabble, or walk, along the bottom of the creek searching for insect larvae attached to rocks.

It is these white water divers that I have come to see. I follow Hansen and his assistant, Alaina Strehlow, over a bridge that crosses Upper McDonald Creek. We stop and scan the water. Seeing nothing, we move on, trying to follow the now softer and slower beeps of the receiver. As Hansen leads us through the thick forest canopy alongside the creek, he explains that he and his crew of biologists, volunteers, and veterinarians have surgically attached radio transmitters to 12 females of breeding age. These transmitters track the birds’ movements and identify each bird’s territory, the area used to forage, mate, nest, and raise its young. By studying the quality of each territory, he hopes to identify how both environmental and human factors are affecting the harlequins’ reproductive success.

Although harlequin numbers are relatively stable throughout the West, it is listed as a species of concern in Montana. With a statewide population estimate of only 150-200 pairs, their older breeding age (3+) and low fledgling success make them more susceptible to environmental and human intrusions. In Glacier, a 10- mile (16-kilometer) stretch of Upper McDonald Creek holds the highest density of breeding harlequins in the state, comprising 25% of Montana’s harlequin duck population.

Due to their colorful appearance and their ability to maneuver frothing whitewater rapids, many visitors to the park flock to Upper McDonald Creek in the spring to see the harlequins return. Park biologists are also interested in watching these birds and since 1999 have monitored the numbers of breeding pairs and chicks reproduced each year. When no chicks were observed in 2010, they began to realize that to successfully manage harlequins, more research was needed.

This is where Hansen comes in. His master’s thesis is a three-year study that began in 2011. In a nutshell, he is looking at two potential factors that might be associated with nesting success: stream flow variation and human disturbance.

The timing and fluctuation of stream flow is important to the harlequin’s nesting success. Waiting for stream levels to drop before laying their eggs and incubating them, females build nests close to the water, usually within one meter of the water’s edge. Although timing and amount of spring run-off is variable from year to year, most streams experience a peak flow followed by a drop off. However, the flashiness of a stream, or how quickly a stream rises or falls in response to weather events, is important. If Upper McDonald Creek is affected by heavy rain or snow melt after reaching its peak flow, the rising water could wipe out the already nesting harlequins.

To determine whether or not stream flow variation shows a correlation with chick survival, Hansen measures the height of Upper McDonald Creek using actual stream data taken on a nearly daily basis from a gauge located just above Lake McDonald. Once he has established an average stream discharge, he can identify significantly high and low water discharge years and compare them with historical brood survey data.

With an average of 2 million visitors a year, human presence is definitely a factor in Glacier National Park. But, it is not understood if, or how, this has an impact on the ducks. So Hansen is tracking his 12 study birds to

map each one’s territory and identify if it is in a section of creek with high human activity. Using a device called an Automatic Receiving Unit (ARU), he is also recording how frequently harlequins are found in high-human use sections of the creek (pull-outs along the Going-to-the-Sun-Road) versus low use sections.

In addition, Hansen is documenting the stress levels in his study group by taking blood at capture, sampling feces, and looking at stress hormones in feathers. If there is a correlation between excessive stress levels in ducks whose territories experience high human use, it may be associated with low reproductive success.

This information is important for resource managers, as new strategies could be put in place to protect the birds. But, if it’s not people causing lower chick numbers, then it’s vital to understand what is. As Hansen explains, “It’s important to be able to document environmental impacts. We can’t change snowpack (amounts) or the weather, but it would be great to understand it,” and consequently how those impacts might affect the harlequin’s ability to survive in the future.

Stepping out of the forest canopy into the bright sunlight, we perch on the side of a steep bank overlooking the creek. Hansen and Strehlow scan the creek. “Over there, two females!” Strehlow proclaims. Using his binoculars to look for leg bands, Hansen determines it’s a female and a chick outside of his study group. Nearby, the researchers soon discover ‘IG’, one of Hansen’s 12 banded ducks and the cause of the transmitter’s activity. As the scientists observe the birds and discuss their movements, I search in earnest to find these beautifully camouflaged brown-gray females. To my amazement, the female and chick are just below a large boulder in the midst of a swirling rapid. I raise my binoculars once more and, after a minute, see two small gray ducks bobbing up and down. Then, in an instant, they disappear, diving under the water.

The chick’s ability to navigate these rough waters right from birth amazes me, and I begin to think how incredible this bird is. It’s clear why people come from near and far to see them. Perhaps it is the harlequin’s uniqueness that draws us to them, and our passion is actually a detriment to the very thing we hope to see. Or perhaps their unique adaptations and particular habitat requirements cannot withstand even the slightest change.


Using 24 years of data from Upper McDonald Creek to assess how brood sizes relate to stream flow, Hansen’s analysis found that higher and less-predictable stream flows are good predictors of reduced numbers of chicks. He states, “Based on the results of this study, and climate change forecasts and its effects on stream flow, harlequin ducks are going to face major challenges in the next 50–75 years.” To meet these challenges, he adds, “… we need to ensure that the ecosystems used during each life history stage are fully intact and functional.”

Is human disturbance a problem? Hansen found there was actually a greater probability of duck pairs occupying stream pools near the road versus other stream habitat. At times, the areas near the pools do have high human use, but the fact that the birds were found frequently at these pools may be because most of the desired deep-pool habitat is disproportionately closer to the road. In addition, the surveys took place in the spring, when the Going-to-the-Sun Road is typically still closed to vehicles. Further research or monitoring is needed, especially as the road receives more use, to document the ducks’ behavioral response to close human activity.

By looking at stress hormones that were secreted during the growth of the feathers, Hansen found that females who exhibited high stress hormone levels were less likely to nest, and concluded that events occurring during the non-breeding season do influence whether or not females will produce chicks.

For now, Glacier National Park’s harlequin population is stable. But in the years to come, this vulnerable, charismatic species will need continued monitoring. With increased visitation and traffic along the Going-to-the-Sun Road and a warming climate, park managers want to make sure harlequin numbers remain stable and that these beautiful little sea ducks remain a part of Glacier’s landscape.

Funding for this project was provided by US Federal Highways, Glacier National Park Fund, and CCRLC’s Jerry O’Neal Fellowship.

Melissa Sladek obtained her MS degree in Environmental Studies with an emphasis in education at the University of Montana. She is the Science Communication Specialist, Crown of the Continent Research Learning Center Glacier National Park.

Terry Peterson is the Office Manager & Education Technician, Crown of the Continent Research Learning Center Glacier National Park.