Few if any fish survive in acid lakes, so loons have less food for their young. Acid rain also increases mercury levels in wildlife: in acidic environments, mercury converts faster to toxic methylmercury.
The dangers of mercury have been well documented in humans, but are less known in wildlife. Lab studies with other birds show that mercury damages the central nervous system, says Neil Burgess, a wildlife toxicologist with the Canadian Wildlife Service. "It tends to disrupt vision and muscle coordination, and is quite toxic to developing embryos," he said. It also seems to weaken immunity, making the birds susceptible to other diseases.
Biologists noticed that on acid lakes, adults outnumbered chicks and young birds. "We started looking at reproduction rates in loons in relation to blood mercury levels," said Burgess. "The higher the level, the lower the reproduction."
Field studies revealed that loon pairs suffering from mercury poisoning rarely nested or laid eggs. When they did, they incubated the eggs poorly. Few chicks hatched, chicks didn't feed well, and parents had a hard time feeding them. Scientists wonder whether vision problems from mercury poisoning may be affecting the birds' ability to catch fish.
Now, researchers are determining exactly how high mercury levels need to be before reproduction decreases or stops altogether.
In a recent study by the U.S. Fish and Wildlife Service (USFWS) in the Adirondacks, about one-fifth of the loons they caught and tested had mercury levels high enough to endanger breeding success.
Evaluating Environmental Impact
Researchers affiliated with the ACLP are creating a "wildlife criterion value," tracking how mercury moves up the food chain, from water and sediment into plankton, crayfish, fish and higher predators.
This will show where exposure is highest and how it accumulates. It will also allow scientists to sample water or lake mud and forecast the concentrations in pike and other big fishor on loons and other species high in the food web, says Schoch.
"It's significant for people, too. We're also eating the fish," she said.
Soon the BioDiversity Research Institute, from Falmouth, Maine, will deliver a report to the USFWS detailing the status of loons, the threats they faceand will present a conservation plan. The Institute is one of ACLP's five partners, which also include the Wildlife Conservation Society, Natural History Museum of the Adirondacks, New York State Department of Environmental Conservation, and the Audubon Society of New York state.
Controlling Air Pollution
Changes to the Clean Air Act (CAA) in 1990 limited sulfur emissions from power plants, regulations which have improved air quality. But research shows that the standards remain too laxand mercury continues to be unregulated.
Even with an additional 80 percent reduction in emissions beyond those required by law, it will take waters a quarter-century to become non-acidic, according to a 2001 report by the Hubbard Brook Research Foundation in Hanover, New Hampshire.
In December 2000, the Environmental Protection Agency announced that it will regulate mercury emissions from power plants. The EPA proposal is due in December, with final regulations to be issued in 2004.
In April, New York State's environmental board approved the toughest acid rain law in the nation, far surpassing federal regulations. "Scores of lakes and ponds in Adirondack Park are dead and remain the culprit of air pollution from power plants," said Eliot Spitzer, New York State Attorney General. "This problem can only be tackled by a federal and state effort to enforce the Clean Air Act."
"We know the dangers of methylmercury," says Pokras. "We need to dramatically change our regulatory and industrial practices to eliminate the mercury in our environment."
Otherwise the wail of the loons is at risk in the northern wilderness.
National Geographic Today, 7 p.m. ET/PT in the United States, is a daily news journal available only on the National Geographic Channel. Click here to learn more about it.
Got a high-speed connection? Watch National Geographic Today in streaming video.
More Bird Stories by National Geographic News:
Tall As a Deer, Huge U.K. Bird Staging a Comeback
Memory Aids Birds in Migration, Study Finds
Crows Better at Tool Building Than Chimps, Study Says
Extinction Near for Albatross, Experts Warn
51-Year-Old Albatross Breaks N. American Age Record
Are Flashy Male Birds Threats to Their Own Species?
Wild and Escaped Parakeets Captivating City Dwellers
Bright Beaks Signal Health to Female Birds, Study Says
Coot Birds Can Count, Study Says
Falconry Used to Secure North American Airports
Cuckoos, Wrens in Escalating Evolutionary Arms Race
Deer Behind Britain's Great Bird Decline?
"Mysterious Plague" Spurs India Vulture Die-Off
Gamblers Fuel Trade in "Lucky" Vulture Heads in Africa
Ospreys Flock to Cuba, With Conservationists Close By
Recent "Birder's Journal" Stories from Robert Winkler:
Giving Thanks for Wild Turkey Sightings
Birder's Journal: Ghost Town's Curse Haunts New England Forest
Birder's Journal: Looking at a Handy New Guide
Birder's Journal: Learning to Let Birds Come to You
Birder's Journal: A Morning With Migrants
Birder's Journal: This Warbler Is a Master of Deception
Birder's Journal: Seduced by Dueling Thrushes
Birder's Journal: Attack of the Flying Goshawk
Nationalgeographic.com Bird-Watching Sites:
Florida Keys Area
Maine's Acadia National Park
New Orleans Area
New York City Area
North Carolina's Outer Banks
Rocky Mountain National Park
Salt Lake City Area
San Francisco Area
Santa Fe Area
South Dakota's Black Hills
Washington's Olympic National Park
Wyoming's Grand Teton National Park
Yellowstone National Park
Yosemite National Park
Additional Information from Related Web Sites:
American Bird Center
American Bird Conservancy
Fish and Wildlife Service Bird Web Site
National Audubon Society
Environmental Protection Agency: Bird Conservation
SOURCES AND RELATED WEB SITES