Threats to Peregrine Falcons
Historically, the use of DDT (Dichloro-diphenyl-trichloroethane) as a pesticide resulted in a rapid decline in the population. DDT and DDE (a breakdown product of DDT) cause eggshell thinning, resulting in the eggshell breaking while being incubated. Today, DDE is still found in some areas and DDT is used in some countries where the peregrine falcon winters. Great-horned owls and golden eagles will occasionally kill young peregrine falcons.
Reasons For Hope
Since the ban on DDT in the 1970's, peregrine falcon populations have recovered significantly, and are even showing signs of recovery in areas in which they haven't been spotted in some years, such as northern NJ.