The Bald Eagle Problem

What happened to the Bald Eagles?

Where did they go?

In the early 18th century, the bald eagle population was 300,00-500,000, but by the 1950's there were only 412 nesting pairs in the U.S. Why did the population drop so quickly?
Bald Eagle catches salmon

First, For the bald eagle's environment

As you can see, the bald eagle are at the top of the food web. Their main prey is salmon, which obviously lives in lakes.

How did they become an endangered species?

In Silent Spring, Rachel Carson writes that researchers have found that, "Since 1947, although the adults have occupied the nest and there is evidence of egg laying, no young eagles have been produced" (Carson 120). This means that there is something wrong with the eggs, which would also explain the drastic population decrease around the 1950's.


But why were the eggs messed up? What was wrong with them?

Well, what else was going on during this time period?

DDT.

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What is DDT?

DDT was a insecticide. Wide use of it on farms started in 1947, which is also when researchers started to notice that no young eagles were being produced, only eggs.

Yes, DDT had an impact on the bald eagle population.

But why? How? What Happened? Well, DDT was an insecticide which was sprayed on farms to kill the pests there. They used cropduster planes to do so.
When it rained, the DDT was washed into the lakes that the salmon lived in and polluted the water. The salmon consumed the contaminated water, and DDT was in them. So, when the bald eagles ate the salmon, they had DDT in them too.
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The salmon wasn't affected by the DDT. They kept on living normaly. Why were the bald eagles affected?

It all has to do with the concentration of DDT. The higher the concentration, the more powerful it is.
Remember that thing called the energy pyramid? It shows energy flow. Well, it can be used to represent the concentration of DDT. The lower levels have the same amount of DDT as the higher levels, but the producers and lower-level consumers have a greater population so the DDT is spread out. As you move up the energy pyramid, the population of each level gets smaller, which means the DDT gets squished together. That means each individual organism in the population gets more DDT, so DDT is more effective.
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What does DDT do?

Remember how we said the same year DDT started being widely used, researchers started to notice how there were no baby bald eagles being produced because their eggs were messed up?
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Well, the DDT in the bald eagles caused them to lay very weak eggs. If anything put any sort of weight on the eggs, they would break. That's why there were eggs around the 1950's, but no baby bald eagles. That's also why the bald eagle population decreased so drastically they were almost extinct.

What if they did become extinct?

If the bald eagles became extinct, it would disrupt the food web and the balance of the ecosystem it used to live in.
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If the bald eagle became extinct, all of the animals it preyed upon would become overpopulated because they wouldn't have a predator, which then would cause a lot of competition between those organisms for biotic (ex. fish for food) and abiotic (ex. rocks for shelter) resources. It would just throw the whole ecosystem out of whack.

Human activities really do have a huge affect on the ecosystem. It doesn't have to be bad, though. We can change it for the better!

Bald Eagle Restoration
P.S- Due to awareness, the bald eagle was recently removed from the endangered species list!