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That eggshell myth was debunked back in the 60s, there is no evidence of any kind that the eggs of exposed birds are any more fragile, but of course it gets repeated so often that nobody ever hears the truth. MOF the use of DDT actually caused the population of all species of birds (including the bald eagle) to increase because the biggest killer of birds is insect-borne disease.

Not that there's necessarily a demonstrated cause and effect, but Bald Eagle and Peregrine Falcon populations have increased greatly since the 60s, since DDT was banned. Since their declining numbers had made these species the prime DDT poster children, on its face the ban seems to have achieved its puropse.
If the DDT banning isn't responsible, what is?

If the DDT banning isn't responsible, what is?

Habitat protection and restoration. Falcons have done especially well since building owners learned how to make their properties more hospitable- when I was working downtown a family lived under a window on a neighbouring building and watching them catch sparrows mid-air was quite a show.

"Not that there's necessarily a demonstrated cause and effect, but Bald Eagle and Peregrine Falcon populations have increased greatly since the 60s, since DDT was banned."

Yes, but bald eagle populations apparently increased from 1941 to 1960 (while DDT was introduced in the 1940s). See my previous post.

Further, there are other chemicals that can cause bird shells to thin (presumably due to insufficient calcium). Lead can cause bird shells to thin. Oil can, too. Mercury can.

http://www.junkscience.com/ddt faq.htm#ref6

Lead started to be removed from gasoline circa 1975, with the introduction of catalytic converters on cars. Lead levels in human blood began to decline at that time (mid-1970s).

Mercury concentrations in the environment have been declining since...well, for at least the last 10 years. Perhaps longer.

Oil spills have dramatically decreased from the 1960s. (Though that doesn't necessarily correlate with oil in the environment, since leaks from automobiles are a larger total source.)

So all of these other chemicals, which have declined in the environment since approximately the same time, may have produced egg shell thinning in wild birds.

Brilliant logic--it's called the fallacy of post hoc, ergo propter hoc (because one event followed another, the cause was the first event.)

Let me show you another: after women got the vote, we had the Great Depression, WWII, Korea, and Vietnam. Thus we can conclude that women are the cause of American involvement in wars of the 20th Century.

Better try another, and better, proof.

Not that there's necessarily a demonstrated cause and effect, but Bald Eagle and Peregrine Falcon populations have increased greatly since the 60s, since DDT was banned. Since their declining numbers had made these species the prime DDT poster children, on its face the ban seems to have achieved its puropse. If the DDT banning isn't responsible, what is?

It was also perfectly acceptable to kill them until the 50's and early 60's in many parts of the country. Perhaps that, along with the increased forest land in this country are repsonsible.