How did DDT affect peregrine falcon eggshells?

The pesticide DDT caused significant harm to peregrine falcon populations by interfering with the deposition of calcium in their eggshells.1

As the birds consumed prey contaminated with the chemical, DDT became concentrated in their tissues through bioaccumulation. This process resulted in eggs that were abnormally thin and highly prone to breakage, which led to a precipitous decline in peregrine falcon populations across much of their global range following World War II. Following the restriction or banning of DDT in many countries during the 1970s, these populations have since recovered.12