Biological Barometers

Osprey research reveals river pollution

By Mark Armstrong

On a hot summer day in 2009, two UM researchers approach an osprey nest perched on a pole along the Clark Fork River east of Missoula. With the help of a student research assistant, the team launches a remote-controlled, mini-helicopter the student built.

Within seconds the tiny craft hovers at nest level, and the mother osprey takes flight from her perch with plaintive cries. Erick Greene, a UM biology professor and renowned bird expert, watches with a practiced eye the wide loops of her flight pattern over the river and back to the nest again. Attached to the underbelly of the mini-aircraft is a small, inexpensive, point-and-shoot camera that records the entire flight in high definition. When Greene examines the flight recording, he is ecstatic.

“Good news! Three healthy chicks,” he says.

During subsequent flights, the news wasn’t as good. In areas where mercury contamination is evident, the flight recordings often showed one or two osprey eggs that never hatched. Since that first successful flight along the Clark Fork River, Greene and his research partners have examined the nests of about 150 ospreys along several western Montana rivers. The team often uses a large truck with an elevating bucket to get to the nests. But during the past two years, they also have relied on the remote-controlled helicopter.

Greene has studied ospreys for 25 years. He began his research at UM in 2006 with partners Heiko Langner, a UM environmental chemist, and Rob Domenech, director of the Missoula-based nonprofit Raptor View Research Institute. The multifaceted team conducts groundbreaking research on a species whose nesting and migration patterns in Montana have not been well-documented until now.

Driven by the need to better understand the challenges ospreys face, the research is aimed at determining the long-term effects of heavy metals such as mercury, lead, zinc, cadmium, copper and arsenic on ospreys and their ecosystems. The famed “fish hawks” of the West provide a perfect indicator species for the research because their diet is 100 percent fish.

High concentrations of mercury found in osprey chick blood samples are the most alarming finding from the research. Blood samples are taken from chicks and not adults because mercury found in the chicks was acquired from Montana rivers where they nest. Their migrating parents accumulate mercury from watersheds outside of the study area. Through the research, levels as high as 800 micrograms per liter (µg/L) have been found in osprey chick blood samples. By comparison, the safe level for human consumption is 5.8 µg/L.

“That doesn’t mean that humans who eat fish from the Clark Fork will immediately have 800 µg/L of mercury in their blood,” says Langner, a German geochemist who has studied heavy metals in ecosystems most of his career. “But it’s certainly a valid reason for concern and continued study.”

Once mercury is absorbed by living organisms, it becomes more concentrated as it moves up the food chain from algae and water insects to fish. It’s a process called bioamplification.

“By the time you get to the osprey at the top, it’s really concentrated,” Greene says. “So what we are trying to do is figure out whether this mercury is having an effect on how the birds are doing, and that’s where the remote-controlled helicopter comes in. Now we can access more nests, and we are finding higher egg mortality in areas with high levels of mercury.”           

Surprisingly, the source of the mercury does not appear to be from the mining and smelting that occurred upstream in Butte and Anaconda. The research team found the highest levels of mercury in a 70-mile section of the Clark Fork River, beginning about 48 miles upstream from Missoula and continuing about 35 miles downstream from Missoula. The team believes that the high concentrations are the result of gold mining along Gold Creek and Flint Creek just upstream from Drummond.

Like most good research, the information collected raises as many questions as it answers. For example, it’s unclear if the high levels of mercury found in the birds impacts their migration patterns and mortality rates.

To deepen their understanding, the researchers began banding the chicks in 2006. Ospreys in Montana migrate to Mexico and the Caribbean each winter, and chicks born here don’t return until they reach maturity three years later. The team now is just beginning to see banded birds return to Montana’s rivers. If small numbers of birds return in the coming years, it’s possible that the birds are ingesting lethal amounts of mercury.

The researchers are optimistic that the additional funding they are seeking for their work will allow them to purchase a satellite banding system – technology that will allow them to keep much better track of the birds as they migrate. This would offer more definitive answers on what is happening after the chicks leave Montana. From Greene’s perspective, however, the greatest benefit from his work may be the groundswell of awareness and enthusiasm the study has generated in the nonscientific community.

“We go wherever there are osprey nests,” he says. “Many of the nests are on ranches, and we spend a lot of time knocking on doors to get permission to do our work. That leads to new friends and partnerships. It seems everyone wants to see the ospreys survive and do well.”

Through their research efforts, the team has created an active and committed citizen-scientist volunteer network – folks who love watching ospreys and keeping records of their observations. The data collected by these amateur ornithologists have greatly increased knowledge about ospreys in western Montana.

In addition, Greene, who Langner refers to as the “ultimate advocate for the program,” works closely with local school districts to provide youth groups the opportunity to observe the research as it’s conducted in the field. Hundreds of Montana schoolchildren have been given rides in the bucket truck and have observed the mini-helicopter in action. And in the process, they’ve learned about ospreys, their habitat and the challenges they face. In addition to being a fun field trip, the research inspires young biologists and stewards.

Last year Greene experienced the most rewarding moment in his storied 30-year career as a wildlife biologist. The event was delivered from an unexpected source. One of the observation nests is located less than 30 feet from the Riverside Health Care Center, located on the north side of the Clark Fork River not far from the University. Watching ospreys is the highlight of the day for many of the residents at the center.

Riverside resident Mary Torgrimson Olson, a former UM Curry Health Center nurse, was one of the biggest osprey fans at the center before she died in 2005, just days before her 91st birthday. She would sit in a viewing room for hours each day watching the ospreys dive into the river for fish, and then fly to and from the nest. When her daughter, Karen Wagner, came to visit, they would watch the birds together.

Shortly after Olson’s death, Wagner began discussions with NorthWestern Energy and Kate Davis of Raptors of the Rockies to help raise money to purchase a nesting pole for the ospreys so their nest could be moved away from dangerous power lines. Bringing this heartwarming story to the attention of NorthWestern Energy paid off. Enough money was raised to purchase a nesting pole that memorializes Olson’s passion for ospreys.

Last spring when the ospreys returned from their southern migration to nest once again along the Clark Fork, the osprey team showed up with a bucket truck and gave Wagner a lift up to the nest to view this season’s chicks.

When the lift lowered her to the ground, Wagner embraced the pole and the plaque created in her mother’s honor. 

“Everyone from the nursing staff, to the residents, and even the burly construction workers, were touched by the moment,” Greene says. “There wasn’t a dry eye in the house.”

For more information, email erick.greene@mso.umt.edu or heiko.langner@umontana.edu.