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In her book, Silent Spring, Rachel Carson called attention to the harmful effects of the pesticide DDT (dichloro-diphenyl trichloroethane) on the natural world. The Channel Islands off the southern California coast provide an ideal laboratory in which to study the effects of DDT on wildlife, learn from our past mistakes and restore the delicate balance of nature.
The Channel Islands, sometimes referred to as the Galapagos of North America, are composed of eight islands located within one of the richest marine and terrestrial environments in the world. Home to many endemic plants and animals, these islands offer an insight into the magnifying effects of DDT through the food web. The story of the bald eagle on the Channel Islands offers one of the best illustrations of DDT’s profound impact on wildlife.
Historically, there were more than 35 bald eagle nesting areas on the Channel Islands, making it a stronghold for the species in southern California. Beginning in the late 1940s and continuing through the early 1970s, millions of pounds of DDTs and polychlorinated biphenyls (PCBs) were discharged into the ocean off of southern California through a wastewater outfall. Feeding on a steady diet of contaminated marine mammals, seabirds, and fish, the bald eagles on the Channel Islands began showing the effects of DDT, although they were miles away from the outfall. The birds began laying abnormally thin-shelled eggs that broke easily in the nest. By the early 1960s, bald eagles disappeared from the Channel Islands due to human impacts, primarily the introduction of DDT and other contaminants into the environment.
The disappearance of bald eagles contributed to the ecological imbalance on the islands. Over time, the absence of territorial bald eagles provided an opportunity for the non-native golden eagle to colonize the northern Channel Islands. Golden eagles became established on the northern islands by the 1990s where they routinely preyed upon the diminutive native island fox. Largely as a result of predation, the Fish and Wildlife Service emergency listed the island fox as endangered in 2004.
Seeking to undo the damage caused by DDT and restore ecological balance to the Channel Islands, a multi-agency effort was launched in 1980 to restore bald eagles on Catalina Island. Between 1980 and 1986, 33 eagles taken from wild nests on the mainland were introduced to Catalina Island. In 1987, the first bald eagle eggs were laid on Catalina Island, but they soon broke in the nest. It became apparent that DDTs and PCBs continued to contaminate the marine food web. Since 1989, the reintroduced population of bald eagles on Catalina Island has been maintained only through intensive through human intervention, including the artificial incubation of eggs.
In 1990, the Service’s Environmental Contaminants Program undertook an extensive Natural Resource Damage Assessment. Through this effort Montrose Chemical Corporation and the other polluters responsible for discharging the DDTs and PCBs into southern California’s marine environment were held accountable. After 10 years of negotiations a settlement was reached, and Montrose and the other defendants agreed to pay a total of $140 million to the government. The Montrose Settlements Trustee Council, a group of state and federal agencies that includes the Service, is responsible for using these funds to restore the natural resources (including bald eagles) injured by the pollutants.
As part of the Montrose Settlements Restoration Program, the Trustee Council initiated a feasibility study in 2002, to determine if bald eagles reintroduced to some of the northern Channel Islands that are farther away from the source of contamination might have greater reproductive success than the birds on Catalina Island. The feasibility study has two aspects: 1) releasing captive-bred and translocated wild nestling bald eagles on Santa Cruz Island, and 2) monitoring contaminants in the released birds, their eggs, and their food to determine DDT concentrations. As of January 2007, 61 birds have been released and there are approximately 30 bald eagles remaining on the northern Channel Islands. Each eagle is equipped with satellite telemetry equipment that allows the biologists to track movements within the Channel Islands and along the mainland. Biologists have tracked birds released on Santa Cruz Island as far north as Washington State, and as far east as Yellowstone National Park in Wyoming.
In the spring of 2006, several significant milestones occurred in this restoration effort. First, biologists first confirmed the presence of two bald eagle nests on Santa Cruz Island and then after an anxious 35-day wait during incubation, each of the nests produced a bald eagle chick—the first successful hatches on the islands since 1949.
"The fact that two bald eagle chicks hatched without the help of humans on the northern Channel Islands represents a significant milestone in the recovery efforts for the entire Channel Island ecosystem," says Kate Faulkner of the National Park Service.
Shortly following the first hatching, a live web cam was set up to allow the public to experience the historic moment. A loyal fan base quickly emerged on an Internet discussion forum that included play-by-play accounts of the activities of the parents and chick. Known to biologists as A-49, this chick was affectionately called "Cruz" and "Junior" by the web cam crowd. "We are thrilled to have been able to share the excitement of watching A-49 grow and fledge with viewers from all over," said Dave Rempel, a biologist for the Institute for Wildlife Studies who monitored the nest. Both of chicks fledged successfully and are now exploring the northern Channel Islands.
Author: Annie Little, Environmental Contaminants Program and Montrose Settlements Restoration Program, Carlsbad, California.
Article reprinted from Fish & Wildlife News. Special Rachel Carson Centennial Anniversary Issue, Spring 2007 (4 MB pdf)