Do chemical poisons in the bald eagles food cause eggs to crack before incubation is complete?

Yes. Farmers used a chemical called DDT on their crops as an insecticide This chemical would leak into the ground and pollute the water, eventually the fish in the water were poisoned and the eagles that ate the fish consumed large amounts of DDT due to biomagnification. Then when the eagles laid eggs, the DDT caused the shells off the eggs to be softer so when the mother eagle was incubating her eggs, they would be crushed.