In the spring of 2006, elated biologists, program staff and dedicated web camera viewers were thrilled to see a tiny Bald Eagle chick appear in a large nest that was built in the top of a 30-foot tree near Pelican Harbor on Santa Cruz Island. This groundbreaking milestone marked the first successful nesting of bald eagles on the Northern Channel Islands in over 50 years! The parents of this first chick were a female known as K-26 and a male K-10 that were hatched as part of a captive breeding program at the San Francisco Zoo (SF Zoo) and released on Catalina Island in 2001 and 2002. Biologists placed large wing markers containing a letter and number on the eagles before they were released on the islands. All eagle chicks receive a wing marker before they fledge from the Channel Islands as well. These wing markers allow biologists to track individual eagles to measure success of their restoration efforts.
Bald Eagles once nested on all of the California Channel Islands. Bald Eagles disappeared from the Channel Islands by the early 1960s, due to human impacts, primarily DDT pollution. Millions of pounds of DDT and PCBs released into the ocean off the Palos Verdes Peninsula between the 1940s and the 1970s continue to move through the food chain. The effects of these chemicals are magnified, causing Bald Eagles to lay thin-shelled eggs that either dehydrate or break in the nest. The last known nesting by Bald Eagles was in 1950 on Santa Rosa Island.
The Institute for Wildlife Studies (IWS), in cooperation with the U.S. Fish and Wildlife Service, the California Department of Fish and Game, and the Catalina Island Conservancy, began a reintroduction program on Catalina Island in 1980. From 1980 to 1986, 33 bald eagles were released onto Catalina Island in an effort to reestablish the species on the island. Some of these birds matured and formed breeding pairs. In 1987, the first eggs laid by the reintroduced birds broke. Analyses revealed that high DDT contaminant levels likely caused the failures. The DDT and associated waste products that remained in the environment were still affecting Bald Eagle reproduction. In 1989, biologists began increased efforts to help sustain the reintroduced population, since the birds could not do so on their own. Biologists climbed into the nests and carefully replaced real eggs with fake ones. The eggs were then brought back to an incubation facility where they were kept warm until the eggs hatched. If chicks hatched, they were fostered back into nests. If too few hatched, captive-born chicks from the SF Zoo were fostered into the nests. Since 1980, more than 100 Bald Eagles were released or fostered into nests on Catalina Island.
In 2002, MSRP initiated a study to determine whether bald eagles reintroduced to the Northern Channel Islands might have greater success hatching chicks than those on Catalina Island. A total of 61 eagles were released from hacking towers on Santa Cruz Island form 2002 to 2006. The eagles came either from the SF Zoo or from wild nests near Juneau, Alaska. The chicks were held in the towers until they where 12 weeks old. The birds were closely monitored following their release to track their survival. The chicks were outfitted with blue wing markers with unique numbers and satellite transmitters. The satellite transmitters allowed the project to track the movements of the released birds. One of the birds traveled as far as Yellowstone National Park in Wyoming before returning to Santa Cruz Island.
The success on Santa Cruz Island has continued since the first breeding in 2006. The birds at the Pelican Harbor nest have hatched chicks every year. Additional nests have been discovered on Santa Cruz and Santa Rosa Islands. In 2010, between 9-15 eggs were laid on Santa Cruz and Santa Rosa Islands of which six chicks hatched; all of which survived to leave the nest. As of December 2010, there are an estimated 34 eagles that currently make the Northern Channel Islands their home.
In 2007, encouraged by the successful breeding of the eagles on the Northern Channel Islands, IWS decided to leave the eggs in two nests on Catalina Island, Pinnacle Rock and Seal Rock, to see if DDT levels were low enough to allow the birds to hatch on their own. In the spring, the project reached another milestone when each nest hatched two chicks -marking the first hatching of eagles unaided by humans on Catalina Island in over 30 years!! Both sets of parents were long-time residents of the island. The Pinnacle Rock pair- K-65 was a 21-year old male at the time from a wild nest in British Columbia released on the islands in 1986 and K-92 was an 8-year old female from the captive breeding program at the SF Zoo released in 1999. The Seal Rock's pair was a 14-year old female,K-34, who was released on the island in 1993 and a 15-year old male, K-25, hatched from an egg taken from the West End nest on Catalina Island and then fostered into the Pinnacle Rock nest in 1992.
Since this initial success, the IWS has decided to let all the eagle pairs on Catalina Island incubate their eggs unaided by human intervention. The results have been impressive. In 2010, a total of seven pairs nested on the island laying 12-16 eggs. Of the eggs laid, 9 chicks hatched and all survived to fledge from the nest.
It will take several more years of monitoring to determine if the reintroductions have created a sustainable Bald Eagle population on the Channel Islands. Monitoring of nesting success and contaminant levels will continue for many years to come. However, the positive results we have seen so far on these islands indicate the program has been successful in restoring this national symbol and important component of the Channel Islands ecosystem!
-Jennifer Boyce
MSRP Program Manager
