Researchers Study Pcb Puzzle Among Hood Canal Bald Eagles It’s A Mystery Why These Birds Have More Problems Than Those On Puget Sound

For years now, bald eagles nesting on Hood Canal have produced fewer chicks than those nesting elsewhere in the state.

“The failure rate we have seen in the Hood Canal area at times is as bad as the worst places in the Great Lakes,” said environmental toxicologist Don Tillitt of the U.S. Geological Survey in Columbia, Mo.

Since about 1980, scientists have known that the problem here is polychlorinated biphenyls, or PCBs: oily manmade compounds once widely used in such things as electrical transformers and the inner hulls of submarines because of their insulating qualities.

PCBs accumulate in the food chain, starting with tiny organisms, building up in fish, and reaching the highest levels in eagles, seals and other predators.

It’s no surprise to find eagles exposed to PCBs in the industrial Midwest.

But it’s a mystery why the birds have more problems here, in a relatively undeveloped area, than elsewhere in the Puget Sound region. Scientists are searching for clues along the shore, in the eagles’ food, and in the birds themselves.

At least 25 pairs of bald eagles are sitting on nests here now, waiting. But some of the eaglets will die in the egg. Their parents will wait in vain and eventually give up.

Shelly Ament, a biologist with the state Department of Fish and Wildlife, has been watching the birds for three years. Twice each year during nesting season, she flies over the area in a helicopter.

“When I fly in early April, I see a lot of eagles incubating on eggs,” said Ament. “When I fly in June, it has been quite the eye-opener to see so many failures of nest sites.”

Healthy females will generally lay one or two eggs each year. In a healthy population, the survival rate is about one eaglet for every nest.

Statewide, the average is 0.96 survivors per nest. And the population as a whole is thriving due to protection efforts over the past 10 years.

But in Hood Canal, the average survival rate tends to be much worse.

In 1994, the rate was 0.41 - less than one eaglet for every two nests. Twelve of the 18 active nests failed to produce any young.

In 1995, the rate improved slightly to 0.54 survivors per nest.

Last year, the rate was a healthy average of one eagle per nest.

But while that sounds like good news, Ament notes that the rates fluctuate wildly. Hood Canal eagles had healthy survival rates in 1986, 1988 and 1990 - but they dropped to alarming levels in the intervening years.

In 1991, state and federal wildlife agencies began working together on the Hood Canal puzzle.

First, researchers collected eggs from failed nests for testing. They found PCB concentrations as high as 23 parts per million, said Mary Mahaffy of the U.S. Fish and Wildlife Service. Other studies have shown that four ppm is sometimes enough to prevent hatching, she said.

Researchers then focused on the birds, carefully trapping them live. PCBs in the blood of four adults and four nestlings suggested at least some toxins were picked up locally in a recent meal. But Hood Canal fish showed no greater PCB concentrations than fish outside the area.

Next they tracked the birds via satellite. Four eagles were trapped and fitted with backpacks containing radio transmitters.

“We already knew that the birds disappear in late summer or fall,” said Jim Watson of the state Department of Fish and Wildlife. “We wanted to see where they went and where they might be picking up contaminants.”

“One bird went down to the Lower Columbia River for about three weeks before heading north,” he said. “The farthest went to Southeast Alaska.”

The study revealed much about the birds’ travels, but not much about contamination, Watson said.

Now University of Washington researcher Sam Wasser, who has studied PCBs’ impact on hormones, has proposed studying the feces of Hood Canal eagles.

If funding is approved for next year, a research team will spread tarps under 16 nests in the Hood Canal region and collect fecal samples during the nesting period. By the end of three years, Wasser’s team may know which eagles are suffering with reproductive problems and whether they are recovering.

But the source of the PCBs is still unknown.

John Calambokidis of Cascadia Research Collective in Olympia believes the problem could be Hood Canal seals.

“We have seen eagles scavenging dead seals,” Calambokidis said.

Seals get the PCBs from fish, he said. Almost 90 percent of the PCBs seals ingest accumulate in their bodies, so the concentrations can be 10 to 100 times higher than in the fish they eat.

“An eagle scavenging a seal carcass would be getting 10 to 100 times more PCBs than if it were eating a fish,” Wasser said.

That still would not explain why Hood Canal eagles are worse off than others in Puget Sound. But perhaps eagles in Hood Canal prefer more seal meat for some reason, or perhaps dead seals are more accessible in that area.