DDT and other pesticides are carried by rain and irrigation into waterways. That tends to concentrate them in aquatic life, especially fish. Bald Eagles have a diet that consists mostly of fish, so they accumulated DDT. That caused them to produce eggs with very thin shells, most of which did not survive. On the other hand, Golden Eagles mostly eat small, land mammals. These animals did not have the high exposure that fish did, so Golden Eagles did not suffer the same problems as Bald Eagles.