DDT thins the egg shells of many birds, especially the eggs of raptors.  The thin shells can not stand the female’s incubation and cracke under pressure, during the time DDT was in widespread use.

Rachel Carson highlighted the dangers of DDT in her groundbreaking 1962 book Silent Spring. Carson used DDT to tell the broader story of the disastrous consequences of the overuse of insecticides, and raised enough concern from her testimony before Congress to trigger the establishment of the Environmental Protection Agency (EPA).