This one has been politicized to the extent that many environmental scientists were doubting the original data that underpinned the ban of ddt. Some scientists in UK went back to their egg collections and discovered that there were specific egg thinnings in specific species of thrushes and wrens that went back to the 1850s and the environmental relationship had to be cobbled together from retrospective data, and much of that data may have been a bit specious. No real follow-on studies have been proposed regarding the wrens and thrushes, except some " shell strength stuidies" at Cornell where they found that egg sheels were variable for smaller birds and that there is a cluster of data re:"biomagnification" , since the egg shells were thinning mostly for carnivorous birds. AS far as the early dates (1850s) I never heard a good explanation /
HOWEVER, having said that the USGSW has produced a clear data driven analysis re egg thinning in Raptors that was based upon data from th early 1900s into mid century
http://www.pwrc.usgs.gov/educatnl/beyer/dde2.pdf
Thisw above appears fairly straightforward. Also, theres a good paper from U CAL on animal toxicology and egg thinning wrt DDE/DDT>(I lost the ref to this in my bookmarks) . Id suggest a search with some ddt and eggshell keywords and look for a uc.edu paper on eggshell thinning
The politicization of this topic runs the gamut from
"Let business control environmental policies". to
"The ban on DDT was a first world plot to control birth rates in the tropical third world"
One of my personal peeves is that most science or environmental reporting in the press is so bad that its hard to believe anything without going back to the original data. Both political sides are guilty of histrionics and made up crap that even credible scientists are being fooled.
Go viswit Fred Singers site, this guy was once a good scientist, now hes a shill.
http://www.sepp.org