Up in the San Bernardino Mountains of Southern California stands a tree on the shore of Big Bear Lake. 145 feet up the trunk of the Jeffrey pine and nestled in between branches is a large nest in which a bald eagle roosts. Her deep brown feathers blend in with the nest’s sticks, twigs, and dried grasses. Her white head and hooked yellow beak, however, stand out from her surroundings.
As soft gusts of wind bristle her feathers and the tree branches slowly sway, the eagle carefully moves some of the twigs aside and slowly rises, revealing two off-white eggs. She gently nudges the eggs and rolls them over before settling down once again.
The eagle watches from her perch as another flies over the lake. This bird is on the hunt. He peers down at the glistening water and keenly searches for a fish to catch. He soon spots a salmon and, with wings outstretched, soars towards his prey. He thrusts his feet forward, opens his talons wide, and swiftly snatches the fish out of the water. The bird flies with the salmon to a nearby tree and enjoys his meal.
Nicknamed Jackie (female) and Shadow (male) by the Friends of Big Bear Valley, a non-profit that monitors and tracks their progress, these eagles are a nesting pair that has been raising eaglets together for a handful of years.
Their routine is a simple one: Jackie sits on the eggs throughout the night while Shadow perches on a nearby branch to keep an eye on any potential threats. During the day, Jackie and Shadow take turns caring for the eggs.
Once the eggs hatch, Jackie and Shadow will continue their routine with one exception: they will now be bringing food back to the nest for their eaglets to eat. It will take 11 weeks until the eaglets start venturing out of the nest. This is the process of fledging, during which the eaglets begin to strengthen their wings and fly. After the eaglets fledge, however, it takes up to another eleven weeks for them to leave the nest and venture out on their own and join the other 316,700 bald eagles that live in the contiguous United States. Almost sixty years ago, however, the bald eagle population was close to extinction.
A once critically endangered species, bald eagles’ lives were threatened by a chemical synthesized in 1874 by Austrian chemist Othmar Zeidler. This chemical is DDT (Dichloro-diphenyl-trichloroethane), a crystalline compound. A white, odorless, and tasteless substance, DDT came into popularity after being introduced during World War II to combat insect-borne illnesses such as malaria. It then proceeded to become an infamous insecticide used in homes and farms across the United States during the 1940s and 1950s.
DDT was reasonably priced, persistent, and versatile, so when people realized its effectiveness as an insecticide, they used it wherever and whenever they could. The fact that the DDT could be applied in the form of paint, powder, and as a spray meant that it could be applied to virtually any surface and virtually anywhere. DDT was painted on door frames, powdered under living room couches, sprayed like Febreze in homes, and even rubbed onto household pets. Usage was not limited to homes. When people went camping or enjoyed a day at the lake they brought a canister of DDT with them, purifying the air around them and ridding the area of pests. Farmers, meanwhile, sprayed DDT onto their fields to exterminate the insects that threatened their crop yield.
By 1945, agricultural and commercial use of DDT became widespread in the United States. DDT was used for over 30 years and during this time approximately 1,350,000,000 pounds were used. Its use reached its peak in 1959 when 80 million pounds of the insecticide were applied in one year and in the US alone. DDT had many detrimental effects on people and wildlife.
When people ingest DDT, it breaks down into products called metabolites which are stored in the body’s fatty tissues. It can then transfer into a pregnant woman’s fetus or her infant during nursing. If exposed to a high concentration of DDT, people may experience vomiting, shakiness, and seizures.
DDT also greatly affects egg laying animals. The majority of an eggshell’s makeup is calcium carbonate crystals. Without an adequate amount of calcium carbonate, eggshells can become thin and fragile. When an egg laying animal ingests DDT, it interferes with their ability to absorb calcium and for the calcium carbonate crystals to securely bond. It was this interference that caused the bald eagle population to dramatically decrease during the 1940s and 50s.
A species that was already on the decline due to hunting and habitat loss, bald eagles were one of DDT’s greatest victims. Often nesting near bodies of water and preying on fish, bald eagles were particularly susceptible to consuming DDT. Through the process of biomagnification, DDT was first ingested by fish and other aquatic life. When the bald eagles ate fish, they were also consuming DDT, which accumulated in their bodies. This made bald eagle eggshells weak, causing them to either break during incubation or simply fail to hatch. The bald eagle population was therefore on the decline and by 1963, only 417 nesting pairs remained.
One year earlier in 1962, American marine biologist Rachel Carson published Silent Spring, a book about the dangers of pesticides and in particular DDT. Carson worked with the US Fish and Wildlife Service during the 1940s and 50s and it was during this time that she researched DDT and reached the conclusion that it was harmful to both humans and the environment. Silent Spring helped draw attention to the dangers of DDT and by the 1970s, only twelve million pounds of the insecticide were used in the US. In 1970, the Environmental Protection Agency (EPA) was formed and took action in 1972 to ban DDT and several other pesticides.
It’s been almost sixty years since Silent Spring was published and almost fifty years since the EPA banned DDT in the US. It took nearly forty years for the bald eagle population to rebound and be removed from the endangered species list after the DDT ban, a sure sign of its success. In 2007, the bald eagles were removed from the list after it was estimated in 2006 that there were over 9,750 nests pairs in the contiguous states. Since 2009, the bald eagle population has quadrupled and continues to steadily grow. In 2019, over 71,400 nesting pairs were counted. One of these pairs was Jackie and Shadow, who continue to roost with their eaglets high up in their Jeffrey pine overlooking Big Bear Lake.
Sources
Cornell University. (n.d.). Bald Eagle Life History, All About Birds, Cornell Lab of Ornithology. Bald Eagle: Life History. https://www.allaboutbirds.org/guide/Bald_Eagle/lifehistory.
Centers for Disease Control and Prevention. (2017, April 7). Dichlorodiphenyltrichloroethane (DDT) Factsheet. Centers for Disease Control and Prevention. https://www.cdc.gov/biomonitoring/ddt_factsheet.html.
Environmental Protection Agency. (2021, March 17). DDT – A Brief History and Status. EPA. https://www.epa.gov/ingredients-used-pesticide-products/ddt-brief-history-and-status.
Environmental Protection Agency. (2016, September 14). DDT Regulatory History: A Brief Survey (to 1975). EPA. https://archive.epa.gov/epa/aboutepa/ddt-regulatory-history-brief-survey-1975.html.
Fact Sheet: Natural History, Ecology and Recovery. Official Web page of the U S Fish and Wildlife Service. (2019, July). https://www.fws.gov/midwest/eagle/Nhistory/biologue.html.
FOBBY CAM. (2021). Big Bear Bald Eagle Cam. YouTube. https://www.youtube.com/watch?v=7utMaDb1W08.
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Silver, J., & Alpern, Z. (n.d.). The effect of DDT on vitamin D metabolism and calcium binding activity in the chick. Chemico-biological interactions. https://pubmed.ncbi.nlm.nih.gov/218742/.
US Fish & Wildlife Service. (2020, December). US Fish and Wildlife Service Final Report: Bald Eagle Population Size: 2020 Update. https://www.fws.gov/migratorybirds/pdf/management/bald-eagle-population-size-2020.pdf.