Osprey population recovered, but new threats emerge

NorthWestern Energy was in Augusta earlier this month putting up a nesting platform for ospreys following a fire this spring from a nest built on a power pole. 

“Traditionally, they look for dead trees, snags, with the tops broken off for a nesting place,” said Marco Restani, NorthWestern biologist, in a statement. “Power poles, especially those with cross arms, are often the choice of younger osprey looking to establish a new nesting site. It is dangerous for the birds, and it is damaging to NorthWestern Energy’s system.”

On the brink of extinction some 50 years ago, the osprey population has made a recovery since the pesticide DDT was banned in 1972. This week, NorthWestern Energy said it is asking for the public’s help in addressing newer challenges for the birds, such as power poles and baling twine.

Erick Greene, a professor and researcher at the University of Montana W.A. Franke College of Forestry and Conservation, said in some ways, the story of the ospreys’ recovery following the ban on DDT is a hopeful one.

“This shows you give nature half a chance, and things will respond positively,” Greene said. “For example, bald eagles, peregrine falcon, and ospreys essentially were all going down the tubes. They’re all doing fine now. It’s a big success story that we lose sight of often.”

But he agreed ospreys face new threats.

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In a news release Wednesday, NorthWestern Energy noted the osprey success story “comes with some conflict.”

“Younger osprey in search of nesting sites to breed and hatch eggs will build nests on power poles, causing outages and putting the birds at risk of electrocution,” NorthWestern said.

So the utility’s crews were in Augusta earlier this month installing deterrents on power poles and putting up a nesting platform to give the raptors a safe place to nest. 

“We don’t know if historically, osprey had been in the Augusta area or not, if the species is colonizing a new area in Montana or recolonizing,” Restani said in the email.

The fire started because the osprey built a nest on a power pole outside the Augusta-area substation, the power company said. The nest caused a fire on the pole, and falling debris damaged equipment and took out the power.

Osprey build nests by dropping sticks onto their target site, so NorthWestern puts PVC pipes above the poles’ cross arms. As designed, the sticks hit the pipe and fall to the ground instead. 

“Five are now installed in the Augusta area, along with a raptor nesting platform to encourage the birds to nest in the safe location,” NorthWestern said.

NorthWestern Energy said it relies on customers to report osprey or other raptors beginning to build nests on power poles so it can remove the sticks before nests are made and eggs are laid.

“The public has been extremely helpful with this effort,” Restani said.

The utility said unsecured baling twine also has devastating, deadly consequences because the birds can get tangled in the twine and cannot escape.

“This spring, the male of a pair of osprey that nested on a platform near Whitehall died after its talons caught in part of a coil of baling twine the birds had picked up and used in their nest,” NorthWestern said.

“It’s really distressing to have this result,” Restani said. “The crew called to remove the dead male said the female had abandoned the nest, which did have a couple of eggs in it.”

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Greene, whose research includes studying ospreys, said Montana has played a role in their recovery. In the 1960s, the raptors were almost extinct.

“I think it was down to only several pairs left in Montana,” Greene said.

People noticed the birds were disappearing, but they didn’t know why. A couple of wildlife biologists, twin brothers, did their graduate work on ospreys in the 1960s and ‘70s, and they figured it out, Greene said.

At the time, Flathead cherry growers were using “oodles” of DDT. It would run off into the lake, little bugs like stoneflies would pick it up, and it worked its way up the food chain, Greene said. A small fish might eat a few bugs, and a bigger fish would eat a few smaller fish, and by the time an osprey was eating a big fish, the amount of DDT was concentrated.

The result was eggshell thinning, Greene said. An enzyme in female osprey grabs calcium and lays it down to make a strong eggshell, but DDT, specifically a byproduct, “gums up” the works.

“The eggshells were paper thin,” Greene said. “So the females would lay the eggs, and when they sat to incubate them, they would just break.”

The twins, Doug MacCarter and the late Don MacCarter, helped trace the problem to DDT, Greene said.

“They’re some of my wildlife heroes,” Greene said. “They helped put together this story and do the sleuthing and figure out the reason.”

DDT was banned, but today, ospreys face new threats.

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Greene said the raptors are particularly vulnerable to baling twine because they like to bring it to their nests, and they and their chicks get tangled up in it and often die before they can be rescued.

“It’s a very slow, hideous death,” Greene said.

Biologists ask people who use baling twine to properly dispose of it. Greene also said all the power companies in Montana, roughly 20 including NorthWestern Energy, signed an avian protection plan that aims to reduce risks and make power lines and poles safer.

He said those aren’t the only problems, though, and the osprey population is declining at least along the Clark Fork River, downriver from the old EPA Superfund site in Milltown.

Mercury levels in the Clark Fork River are “way, way too high,” Greene said. He also said toxins around another industrial site downriver, a former paper mill in Frenchtown, may be causing problems.

“Populations are sort of crashing in some areas around here,” Greene said.

A drop in trout numbers in the Clark Fork River may be a factor as well, he said. In the past, a fish count used to yield 2,000 to 3,000 fish per mile, but now it’s down to 100 fish or fewer per mile. Low flows and hot water aren’t good for trout. 

“Fisheries biologists are very concerned that certain species of trout are tanking in some places in Montana, and since that’s all ospreys eat, they may be having a really tough time of it, too,” Greene said. “That’s more speculative.”

But he said ospreys are “a great sentinel species” because they alert people to things that may be problems. Fifty years ago, they told people DDT was a problem.

“Now, they’re telling us other things, that maybe the warming rivers are a problem,” Greene said. “We’re really lucky. People love ospreys, and they still are really common. We’re fortunate about that. But they are really a good species. They’re a window, sort of an early warning system, for problems that may be going on, especially in our streams and rivers and lakes.”