Tuesday, December 1, 2009

DDT and the Bald Eagle

In 1948 Paul Herman Muller, a Swiss chemist, was awarded the Nobel Prize in Physiology or Medicine for his discovering of the use of the chemical Dichlorodiphenyltrichloroethane as an insecticide. This chemical was used to kill mosquitoes during Word War II, which lead to a decline in the number of people inflicted with malaria. After the war the use of the chemical was expanded and it was used as an insecticide on most farm fields.
It was not until 1962, with the publication of a book called Silent Spring, that people began to look at the long term effects of the use of chemicals. In the book Silent Spring, marine biologist and author Rachel Carson documented the effects of chemical pesticides on the environment.
In particular Carson noted that the chemical Dichlorodiphenyltrichloroethane, better known as DDT, seemed to cause birds to produce thinner egg shells which resulted in decreases in the population of several bird species. DDT would travel up the food chain as insects with the poison in their system would be eaten by fish or small birds. The poison would be transferred to the fish or bird which would then get eaten by a larger bird. DDT would build up on birds that were higher up in the food chain each time they would eat some infected prey. Eventually the DDT would alter the birds calcium metabolism resulting in the production of thin shelled eggs that would usually break during incubation.
DDT effected many species of birds but some of the birds that were hit the worst were pelicans, brown pelicans worse then white, peregrine falcons, golden eagles and bald eagles. Silent Spring helped to launch the environmental movement and caused an uproar that eventually led to the ban of DDT in the US in 1972. Since DDT was banned all of the species mentioned above have made significant recoveries and all of those that were listed on the Endangered Species List have since been delisted.
The last to be removed from the Endangered Species List was the bald eagle which was removed in 2007. Bald eagles sightings are now quite common here in Minnesota. There are more eagles in Minnesota then any other state in the continental US. In 2007 they had counted 1312 nesting pair in Minnesota, in comparison their were only around 400 nesting pair in the entire continental US back in 1963, which was the year that I was born. In the winter eagles from all over Minnesota, Wisconsin, Michigan and south central Canada congregate in several locations in southern Minnesota where they can find open water in which to fish. Reeds Landing is a small town on the Mississippi that sits across from where the Chippewa River empties into the Mississippi. The water typically stays open all year which is why you can great views of eagles like the ones above if you are willing to brave the intense January weather in Minnesota.


Jim said...

Great captures over the water.
Sydney - City and Suburbs

eileeninmd said...

Wonderful shots of the Eagle over the river. Great captures. It is wonderful to see the Eagles doing so well.

Loran said...

That is a really great series! Also interesting about the DDT. I'm so glad for Rachel Carson.

Quilt Works said...

great capture - the images are so sharp!

... Visit my contribution "Martha's Vineyard Sunset"

Unknown said...

Amazing how little can bring about a ripple effect to the ecology.

Lovely photos.

Chie Wilks said...

wow..awesome shots of these big birds in action...thanks for sharing the information

mine is here

GreensboroDailyPhoto said...

A very beautiful and IMPORTANT post ecobirder!!!

bathmate said...

I liked it.