How the American bald eagle ‘returned’ from the brink of extinction

Subject : Environment

Section: Species in news

Context:

The American bald eagle was removed from the United States list of endangered species on June 28, 2007.

Details:

A 2021 report by the US Fish and Wildlife Service said that the number of bald eagles in the wild has quadrupled since 2009.
Few decades back the bird was on the verge of extinction.

Threats include:

Hunting:
- Bald eagles began to be seen as a threat to livestock, especially domestic chickens and started to be hunted.
- They were also hunted for their feathers.
Habitat destruction
Widespread use of DDT led to their population decline:
- Water bodies were soon contaminated with DDT due to its use as an insecticide, which in turn contaminated the fish in them. The chemical would enter the bald eagles’ bloodstream when they would eat these fish.
- DDT resulted in female eagles laying extremely thin-shelled eggs, leading to nesting failures.
- Consequently, by 1963, only 417 nesting pairs were found in the continental United States (minus Alaska). This was, after 18 consequent seasons of large-scale nesting failures, as per experts.
- Notably, like the bald eagle, birds such as ospreys and peregrine falcons also faced a similar dropoff in population.

Protection efforts:

Silent Spring, the ban on DDT and the Endangered Species Act
- A nationwide ban on the use of DDT for agricultural use was introduced in 1972.
  - In 1962, Rachel Carson’s book Silent Spring was published. This book, for the first time, documented the detrimental effects of chemical pesticides on the environment and meticulously described how DDT was the prime cause behind the decline in bald eagle populations.
- In 1973, the Endangered Species Act was enacted.
  - The bald eagle was one of the original species listed for protection under this act.

Captive breeding programmes were launched in the 1970s.
- A practice known as hacking was commonly used by conservationists. Hacking is a controlled way to raise and release bald eagles into a wild viable environment from artificial nesting towers.
- This method simulates a wild eagle nesting site and aids in recovery in an area where re-population is desirable.
- Any construction activity was barred within a radius of roughly 100 m of a bald eagle nesting site.
In 1995, the bald eagle was moved from “endangered” to “threatened” status and in 2007, it was delisted completely.

DDT:

DDT or dichloro-diphenyl-trichloroethane was first synthesised in 1874.
However, it was in 1939 that it was first promoted as an insecticide and began to be used to kill malaria-carrying mosquitos and agricultural pests.
By the mid to late 1940s, DDT was being widely used for agriculture across the US.

About the Bald Eagle:

The bald eagle (Haliaeetus leucocephalus) is a bird of prey found in North America.
Its range includes most of Canada and Alaska, all of the contiguous United States, and northern Mexico.
The bald eagle is an opportunistic feeder which subsists mainly on fish.
Bald eagles are not actually bald; the name derives from an older meaning of the word, “white headed”.
The females are about 25 per cent larger than males. The yellow beak is large and hooked. The plumage of the immature is brown.
The bald eagle is the national bird of the United States of America and appears on its seal.
In the late 20th century it was on the brink of extirpation in the contiguous United States. Populations have since recovered, and the species’ status was upgraded from “endangered” to “threatened” in 1995, and removed from the list altogether in 2007.