[MayDay72]

Sprayed on crops and ingested by birds such as the eagle, DDT caused a softening of their egg shells. -From article

That one isn't true either. -Carry_Okie

Interesing. I've often heard the "soft egg shell" and DDT connection mentioned by the scientific community. Especially here in California in relation to the California Condor. Has this now been proven as untrue?

[Gladwin]

DDT breaks down into other chemicals, and it's those chemicals that have the effect on the eggs.

I've heard of two possible mechanisms. The first is that the chemicals weaken the eggs.

The second possible mechanism is that DDT makes birds healthier by killing off their parasites. Then, the birds have huge clutches of eggs. However, they don't eat enough calcium to produce thick shells on all the eggs. So, the birds crush their own huge brood by sitting on them.

Apparently, in captivity, the birds will have good eggs even if they are fed DDT. This is because they are well fed in captivity, compared to the wild.

Still, it's pretty undeniable that as DDT and its' components have declined in the wild, large birds have rebounded and do not have soft eggs anymore.

The pro-DDT sites should not be considered neutral. That said, DDT is a useful chemical because of its' cheapness and effectiveness. It still can be used in the USA if needed to stomp out a disease carrying mosquitos, etc. It also can act as a repellent to some insects, too.

It shouldn't be used in agriculture because this builds up a resistance in the insect population that only time can remove. This is bad for wildlife populations and human populations. Think disease again - you don't want the mosquito population to be resistant to DDT when you are trying to eliminate some yellow fever outbreak.