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December 2020
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ONLINE NEWSLETTER
 
IN AN EGGSHELL
By Alexa Johnson

It's that  time of year again, egg-laying season on Catalina Island has arrived. It’s time to tune in to the Institute for Wildlife Studies’ (IWS) live bald eagle web cams at IWS.org! But before you do, here’s a brief recap of why the story of the bald eagle’s recovery is such an inspirational tale.

Historically, bald eagles could be found across the United States and on all of the Channel Islands. But by the 1950s, our nation’s symbol was on the brink of extinction. Habitat loss, hunting, poisoning and an unfortunate series of other factors contributed to the decline of this magnificent species prior to the 1940s. The most significant cause of its downfall was the industrial pesticide DDT (Dichloro-diphenyl-trichloro ethane). DDT was used across the American landscape to combat bugs of all kinds. This chemical’s persistence in the environment, which was advertised as one of its great benefits, became a huge liability.

DDT accumulated in waterways, lakes, and oceans – all across the continent. This bioaccumulation began to impact many species. To make matters worse for California and for Channel Islands eagles, at least 2,400 metric tons of DDT wastes were dumped into San Pedro Bay between 1947 and the 1970s, creating high localized concentrations of the stuff.

DDE -- a metabolite or residual of DDT poisoning -- affected egg production in bald eagles, pelicans, ospreys and other birds, by causing them to lay eggs with abnormally thin shells. The DDE affected the exchange of gases through the shells’ membranes. The impaired eggs would crack under the weight of incubating parents. Unable to successfully reproduce, birds plummeted in numbers and bald eagles disappeared from the Channel Islands.

IWS came to the rescue in 1980, reintroducing bald eagles to their historic Channel Islands range. IWS biologists spent decades painstakingly monitoring the reintroduced adult eagles on the islands. Once adults began laying eggs, the scientists would retrieve the eggs and hatch them in the safety of their off-site incubation facilities. Once the eggs hatched, the biologists would return the chicks to the nests, where the parents accepted them back and raised them. IWS’s diligent work brought these charismatic birds back to Catalina. Without the human intervention, the Channel Islands eagles probably would have remained absent from their former oceanic range.

In 2007, IWS made the daring decision to not intervene. The scientists allowed eagles to lay eggs in two nests, then attempt to hatch their young naturally. It turned out that DDT levels had finally decreased enough to allow bald eagles to successfully hatch eggs in the wild!

By 2008, all bald eagle nests on Catalina were left alone by IWS so that the eagles could go through the natural hatching and incubation processes. Thanks to the dedication of the IWS, working in cooperation with the Catalina Island Conservancy, our nation's great symbolic animal could be seen soaring above Catalina!

Nest by Nest

Contributing to this edition was Frank Hein. Special thanks for this issue go to Peter Sharpe, Ph.D., and Maria Dominguez, both of the Institute for Wildlife Studies

Edited by Jerry Roberts

THE ISLAND NATURALIST
Issue #22 / All About Bald Eagles


IN THIS ISSUE...


In an Eggshell 
What to Expect
Fact or Fiction? Knowing Resident Baldies
Did You Know … Eaglets Need Moms’ Warmth    





Photo by  Carlos de la Rosa

Thanks to the diligent work of the Institute for Wildlife Studies, in cooperation with the Catalina Island Conservancy, bald eagles have returned to the California Channel Islands and are successfully reproducing on their own.





Missed recent issues?
Issue #1 / All About Bison

Issue #2 / All About Birds

Issue #3 / All About Plants
Issue #4 / All About Eagles
Issue #5 / All About Ravens & Crows
Issue #6 / All About Natives & Invasives  
Issue #7 / All About Rain
Issue #8 / All About Bison Roundup
Issue #9 / All About Foxes
Issue #10 / All About Weeds
Issue #11 / All About Eagle Hatchlings
Issue #12 / All About Snakes
Issue #13 / All About Diurnal Raptors
Issue #14 / All About Diurnal Raptors II
Issue #15 / All About Giants & Dwarves
Issue #16 / All About Fire Ecology
Issue #17 / All About Mule Deer
Issue #18 / All About Feral Cats
Issue #19 / All About Acorn Woodpeckers
Issue #20 / All About Tachi the Fox
Issue #21 / All About Observing Nature



 

 

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