Originally, I believe it was DDT back in the 70's.
I remember hearing that it had the same effect on the eggs of California Condors, bringing them to the brink of extinction as well.
Absolutely correct. In the late 70's there were only 3 active nests in the entire state of Ohio, none of which were producing viable eggs. Eggs from Tennessee were planted in these nests, and the program took off, as DDT was banned and the local population grew. I was a volunteer nest monitor for the Ohio Division of Wildlife until around 2000, and I remember the celebratory mood as Ohion hit 100 active nests. I was honored to be able to participate in that program. Our eyes let the experts know of any nest damage or harassment, how many eaglets were produced and if they were feeding, if the parents were behaving normally, etc. It was time consuming to watch the nests and fill out the reports, but it was awesome and fulfilling to share in the success of their comeback.
