How a 1974 release helped peregrine falcons reclaim their place in North America

In the early 1974s, American peregrine falcons were struggling to survive in parts of North America. Years of DDT use had left many eggs with thin shells that could crack during incubation, leaving fewer chicks to hatch. Conservationists responded by breeding the birds in captivity and releasing them into the wild. According to the National Park Service (NPS), more than 6,000 American peregrines were released through recovery programmes. Restrictions on DDT and legal protection also played a part in the comeback. Along Alaska’s rivers, long-term surveys later recorded a rise in nesting pairs. The American peregrine falcon was removed from the US federal endangered and threatened species list in 1999.Peregrine falcon subspecies faced different levels of pesticide riskThe decline of peregrine falcons was closely associated with the use of DDT, an insecticide that became widespread during the mid-20th century. As the chemical passed through food chains, residues accumulated in birds of prey. Its breakdown product, DDE, interfered with eggshell formation, leaving eggs too fragile to withstand the weight of an incubating adult. Fewer chicks survived to hatch, putting pressure on populat...