Oregon Field Guide producer Vince Patton revisits the status of bald eagles in the Pacific Northwest in this episode, which just aired tonight. Bald eagles are right up there with the Northern spotted owl as the most famous endangered species.
But, as you see in this video, the eagles have a much happier story to tell these days. Their numbers in Oregon are up from 20 nesting pairs in the 1950s and 60s to 700-800 pairs today.
The big problem for eagles, and many other birds, was the pesticide DDT was weakening their egg shells and killing baby birds before they hatch. DDT was banned in the U.S. in 1972, and eagle populations have rebounded to the point where they were removed from the Endangered Species List in 2007.
But bald eagle eggs are still revealing new information to scientists today – particularly about the Columbia River. As I reported for OPB radio this morning, U.S. Fish and Wildlife Service researchers collected new eagle egg samples from various places in the river basin last year.
According to Jeremy Buck, a contaminant specialist for the U.S. Fish and Wildlife Service, the eggs offered at least four key insights about toxins in the Columbia River:
- DDT is still haunting fish and wildlife in the Columbia in the form of its byproduct DDE.
- Dioxin, another toxin that damages eagle eggs, has dropped dramatically – probably because of restrictions on how much of it pulp and paper mills can discharge into the river.
- One section of the lower Columbia River estuary have higher toxin levels than the rest of the river.
- Eagles in that section of the river – between Astoria and Cathlamet – have a lower reproduction rate than those in the rest of the river, which raises questions about how they might impact young salmon in that area.
Buck said the 2010 samples were the third set of eggs researchers have examined since the 1980s.
The toxic hot spot in the Columbia isn’t the result of one big polluter in the estuary, said Mary Lou Soscia, Columbia River manager for the Environmental Protection Agency.
The area between Astoria and Cathlamet is just the “bottom of the river” where all the sediment and toxins wind up because of the way the river widens and slows down as it approaches the ocean.
The “eagle mystery”
Federal scientists noticed in the 1980s that bald eagles in the Columbia River estuary were producing fewer babies. Normal reproduction is one baby produced per nest per year, and 30 years ago eagles in the lower Columbia River estuary were producing about half that.
Since then, eagles from other areas have moved in and built nests there, and the overall numbers have gone up to 150 eagle pairs from the mouth of the Columbia to Bonneville Dam.
Now, according to the latest egg samples, the eagles between Astoria and Cathlamet are producing .8 babies per nest per year.
“They’re not quite there yet, but they’re improving,” said Buck. “And as you go upriver, toward Portland and Bonneville Dam, those eagles seem to be producing at normal rates.”
The dioxin dropoff
That dioxin was a well-known byproduct of the bleaching process used by pulp and paper mills, though there are other lesser sources of it as well. As it was discharged into the river, it accumulated in fish and was passed onto eagles that ate the fish.
Buck said eagle embryos exposed to higher concentrations of that dioxin – between 100 and 200 parts per trillion – become deformed or fail to hatch In the 1990s, he said, eagle eggs in the lower Columbia River estuary contained 400 parts per trillion.
Researchers at the U.S. Geological Survey were also collecting osprey eggs from the Columbia and Willamette rivers during that time. And the levels of TCDD weren’t as high in the Willamette as they were in the Columbia, said Buck.
“That’s a good indicator that the TCDD was coming from pulp mills in the Columbia,” he said.
Pulp and paper mills started phasing dioxin out of their wastewater in response to new regulations from the Environmental Protection Agency in 1991.
“When we looked at dioxin, it was pretty much a big shock,” said Buck. “We saw a substantial decline – a 75 percent decline in dioxin concentration. Much more than we saw for all other chemicals.”
Eagle eggs collected last year contained 75 percent less dioxin than the ones collected in the mid-1990s.
The ghost of DDT
Whereas dioxin levels are still significantly higher in the lower Columbia River estuary than they are elsewhere in the river, DDE def seems to be more evenly distributed, Buck said.
It’s also slower to break down and disappear from eagle eggs than researchers had hoped.
“We really suspected DDE and dioxins would have declined in that additional 10-15 year span,” said Buck. “We collected eggs and found DDE was actually still fairly elevated in upriver nesting birds. It declined, but not that much.”