New threat for peregrine falcons?
What do your computer and a peregrine falcon have in common? For most of us in rural New England, it isn’t speed. Rather it is polybrominated diphenyl ethers (PBDE), a group of chemicals used as flame retardants. There are dozens of varieties of PBDE. Furniture foam contains penta-BDE, computer plastics use octa-BDE, and TV cases and upholstery often have deca-BDE.
The chemical prefixes signify the average number of bromine atoms per molecule of diphenyl ether. Unfortunately, peregrine falcon eggs contain traces of all of these chemicals.
Peregrines are distinctive birds. Nesting on high ledges overlooking open areas across North America, they prey largely on other birds. With long pointed wings they swoop down from their high perches at speeds exceeding 200 m.p.h., snagging their victims with their powerful talons.
Peregrines were on the U.S. Endangered Species List until about 10 years ago, when their populations began to recover from the effects of organochlorine pesticides, such as DDT, which weakened eggshells, rendering embryos unviable.
In New Hampshire and Vermont peregrine populations were wiped out in the 1960s; but by the 1980s -- thanks largely to the DDT ban in 1972 and intensive management -- they staged a comeback. The successful reintroduction of peregrines in northern New England and other regions of the country is heralded as one of the greatest conservation success stories in North America. However, some scientists are now concerned the bird may face another chemical threat.
The worry is over the possible impact of PBDE that is accumulating in the birds. Traces have been found in human breast milk, and in various species of other mammals, birds and fish throughout much of the world, including the Arctic. Scientists aren’t sure how PBDE enters the food web.
It may be from releases during manufacturing, aging and wear of products, or, for humans, direct exposure.
Swedish researchers first discovered the flame retardants in wildlife in 1981, when it was found in certain species of fish. More recently they found high levels of deca-BDE in peregrine falcon eggs. In North America some scientists have begun to document levels in the bird’s eggs to help measure its possible impact.
Because peregrines are at the top of the food web, they often get the brunt of any chemicals that bio-accumulate, making them effective indicators of environmental risk. Vermont and New Hampshire biologists have been playing a role in PBDE studies by monitoring the bird’s populations and by finding samples of unviable falcon eggs and shipping them to laboratories for analysis.
One of those is Vermont-based biologist Steve Faccio. He has been rappelling down cliffs in the state to reach peregrine nests to band chicks in the monitoring effort.
"A volunteer climber and I hike to the cliff top, anchor our gear and repel to the nest ledge," says Faccio. A band with a colored alpha-numeric code is placed on the leg of each chick to allow researchers to track its movements when resighted. "Actual collecting of an egg is always the first thing I do upon arriving at an eyrie," Faccio says. "I carefully slip the greenish-brown egg into a plastic jar padded with foam to carry it back safely."
Faccio and other biologists have collected more than 100 unviable falcon eggs from across New England. The eggs are sent to a team of scientists from the Virginia Institute of Marine Science, The College of William and Mary, the U.S. Fish and Wildlife Service and the National Wildlife Federation.
In an initial report, the scientists say they have found unusually high levels of PBDEs in the peregrine eggs. Two eggs collected in New Hampshire exhibited "extremely high levels" of total PBDEs, concentrations that "rival the highest PBDE burdens reported in wildlife to date," they wrote in an article in the journal "Environmental Science and Technology."
What was unexpected was the amount of deca-BDE in the falcon eggs. Although total PBDE remained steady over the 10-year study, concentrations of deca-BDE, once thought to be too big a molecule to cross cell membranes, appear to be doubling in falcon eggs every five years. Deca-BDE remains the major PBDE in production worldwide.
PBDEs, in birds, do not produce the eggshell thinning associated with DDT. But in laboratory animals it has been shown to cause neurobehavioral, liver and thyroid problems.
"We don’t yet know the threshold for negative effects from PBDEs in falcons; and since peregrines are doing relatively well in the region, I don’t think we are seeing those effects yet," says Margaret Fowle co-director of the Vermont Peregrine Falcon Recovery Project, a partnership between Audubon Vermont, the Vermont Fish and Wildlife Department and other organizations.
Vermont had a record 38 nesting pairs in 2008, while New Hampshire had 18 nests producing nearly 50 percent more young than a decade ago. "It is our hope that our monitoring efforts will detect any negative declines in the population, which may or may not be due to PBDEs," says Fowle.
Kent McFarland is a biologist with the Vermont Center for Ecostudies. The illustration for this column was drawn by Adelaide Tyrol. The Outside Story is assigned and edited by Northern Woodlands magazine and is sponsored by the Wellborn Ecology Fund of New Hampshire Foundation: firstname.lastname@example.org
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