Fifty years after they were decimated by pesticide contamination in one of their strongest marine footholds in North America, American bald eagles are poised for a momentous return.
National Park Service officials plan to reintroduce the birds to the northern Channel Islands off the coast of southern California this summer. As part of a five-year study, a dozen chicks annually will be released on the islands to determine whether they can survive there as they have in other parts of the country.
The program is being funded by a $145 million natural resources damage assessment against the Montrose Chemical Co., the Los Angeles pesticide manufacturer that dumped an estimated 1,800 tons of DDT into the ocean between 1947 and 1971. The settlement, which came after a 10-year legal battle, is the second largest of its kind in US history, after the Exxon Valdez Alaskan oil spill settlement.
The devastating effects of DDT still linger because it does not break down in the environment and can remain in the tissues of fish and birds that have had either direct contact with it or have eaten contaminated prey.
In restoration projects on one of the Channel Islands in recent years, the remaining effects of DDT still present on the ocean floor nearby have thinned the shells of bald eagle eggs, causing chicks to die.
But the four islands to be studied Santa Cruz, Anacapa, Santa Rosa, San Miguel are further from the contamination site and officials hope that through extensive monitoring, the same fate can be avoided.
"This is a very important project in the greater context of the American bald eagle comeback to North America," says Laura Valoppi, a biologist with the US Fish and Wildlife Service.
Brought to the brink of extinction by development and the widespread use of DDT in controlling mosquitoes in coastal and wetland areas, the only eagle unique to North America was listed as endangered throughout the lower 48 states after the Endangered Species Act was passed in 1973. But the DDT ban, strict enforcement of the Endangered Species Act, and methodical application of restoration projects in a half dozen areas have brought the eagle's numbers to levels at which federal protection isn't needed: Now about 5,000 breeding pairs nationwide.
"What makes this crucial is that this is one of the key coastal areas in the country where the bald eagle was once very strong but has not yet come back," says Ms. Valoppi. To see if that will happen, the six-agency project will release 12 eagles into the wild this year, possibly as early as May, and at least 12 each year for the next 3 to 5 years. The eagles would come from a breeding program at the San Francisco Zoo that provided chicks for other projects.
In a process known as "hacking" the birds are placed atop tall, wooden poles to simulate a nest environment. The birds learn to live in the wild; many of them migrate elsewhere permanently, while some never leave, and others leave but later return permanently.
The process is slow. Of more than 70 bald eagles released over 10 to 15 years on Catalina Island to the south, only about a dozen now reside there permanently.
Experts say about 24 pairs of nesting birds existed on the four northern islands before their precipitous decline.
"The birds are very adaptable if they can avoid the imprint of too many humans," says Dan Welsh, contaminants coordinator for the Fish and Wildlife Service. "If they are fed by their own parents and carefully released with proper food, they can learn to hunt on their own in about eight weeks and become like wild birds."
Using $30 million of the settlement money, officials will utilize radio and satellite technology to monitor the flight and eating habits of the birds.
Until now, biologists have marked birds with red wing-tags and relied on the sightings of birders, or park and other officials. But new global positioning systems (GPS) technology will allow researchers to check the birds' immediate whereabouts via computer screens which relay tracking information from satellites.
Such information will help analysts interpret eagle feeding patterns for example, a pattern of feeding on the carcasses of elephant seals known to carry the poison DDE, a byproduct of DDT would reveal important information. This information will also aid in recapturing the birds for necessary, regular testing to chart their health.
"This is a very cool new surveillance method that will be a quantum leap over conventional radio telemetry techniques and the binoculars of folks who happen to pick up the wing tags," says Valoppi.
The eagle restoration project is also part of a longer-term effort by the National Park Service and others to restore native, biodiversity to the Channel Islands. The introduction of pollutants and non-native species such as pigs and rabbits have added to the impact of DDT in decimating populations of brown pelicans, peregrine falcons, and elephant seals. Over the past 20 years, such species have been returned to bountiful levels.
"This new program for eagles is one of the success stories in environmentalism which is so discouraged by losses and declining ecosystems," says Kate Faulkner, chief of natural resource management for the Channel Islands National Park. "It is definitely a way to show people that if we make sound scientific decisions we can make positive ground in saving key ecosystems from further degradation."