The peregrine falcon was once a widespread and successful bird of prey, known for its incredible speed and hunting prowess. However, by the middle of the 20th century, the peregrine falcon population had crashed precipitously, and the species was completely extirpated from many areas of its former range. A variety of factors contributed to the decline and eventual extinction of the peregrine falcon.
Widespread Use of Pesticides
One of the primary causes of the peregrine falcon’s extinction was the widespread use of certain pesticides like DDT in the decades after World War II. While DDT was effective at controlling insect pests on farms, it had unintended consequences for predatory birds like the peregrine falcon.
DDT and its chemical byproducts accumulated in the bodies of peregrine falcons through the food chain, since peregrines preyed on smaller birds who had ingested DDT. Over time, the toxic pesticide interfered with peregrine reproduction by causing females to lay eggs with thin, fragile shells. When adult falcons tried to incubate these thin-shelled eggs, they would often crack and break, preventing embryo development.
Studies in the 1960s and 70s estimated that only 1-2% of peregrine falcon eggs laid produced fledglings, compared to normal hatching rates of around 80%. This drastic reduction in reproductive success meant that peregrine populations could not sustain themselves and began to crash towards extinction.
Habitat Loss and Disturbance
In addition to pesticide use, the peregrine falcon was negatively impacted by extensive habitat loss and increased disturbance of its nesting sites. Peregrines nest on tall cliffs and bluffs, usually near bodies of water where they hunt. However, shoreline development expanded dramatically in the 1940s-1960s.
Construction of dams, bridges, and buildings encroached on historical peregrine nesting habitats. Quarrying operations also claimed nesting sites, while increased recreational activities like rock climbing and hiking disturbed falcons at sensitive nesting areas during the breeding season.
Without secluded nesting cliffs free of human disturbance, peregrine falcons could not successfully lay eggs and raise young. The growing scarcity of high-quality habitat exacerbated population declines.
Illegal Hunting and Trapping
Despite being protected under the Migratory Bird Treaty Act starting in 1918, peregrine falcons were still illegally hunted and trapped during the mid-20th century. The large size, speed, and ferocity of peregrines made them prized targets for falconers and trophy hunters.
Collection of peregrine eggs and chicks from the wild also continued, to stock falconry mews. Although illegal, these activities still claimed a number of adult and young peregrines each year, further suppressing populations.
Decline of Prey Species
The primary diet of peregrine falcons consists of mid-sized birds like pigeons, doves, waterfowl, shorebirds and passerines. However, populations of many avian prey species also declined in the 20th century due to habitat loss and pesticides.
With fewer birds available to hunt, starvation likely became a problem for some peregrine populations, especially juveniles learning to hunt on their own. A lack of prey compounded other threats to peregrine survival.
Range Contraction and Extinction
Faced with this combination of threats, peregrine falcon populations contracted severely, undergoing steep declines between the 1940s and 1970s. The species was completely extirpated across much of its former range, including the entire eastern United States by 1964.
Only small, scattered western populations remained, with an estimated 324-485 breeding pairs left in North America by 1975. With numbers this low, the peregrine falcon was endangered with imminent extinction.
Recovery Efforts
Once the threats facing the peregrine were recognized, intensive recovery efforts began. The banning of DDT in 1972 and 1973 allowed eggshell thickness and hatching rates to gradually recover. Captive breeding programs supplied falcons to repopulate former range.
Nesting boxes and hacking programs gave new generations of falcons a needed boost. Thanks to these efforts, peregrine populations rebounded significantly by the 1990s. From extinction, the species was downlisted to ‘threatened’ and eventually delisted from the Endangered Species Act in 1999.
Lessons Learned
The extinction of the peregrine falcon taught us that even widespread, high-profile species can be driven to the brink by human impacts like pesticides and habitat loss. But the recovery also showed that with quick action and persistence, even dire population crashes can sometimes be reversed.
The peregrine now stands as an iconic example of effective wildlife conservation, made possible by environmental regulations banning harmful chemicals like DDT. However, ongoing threats such as climate change and habitat degradation mean that continued monitoring and protection efforts may be needed to ensure the falcon’s long-term survival.
Conclusion
In summary, the peregrine falcon was driven to extinction by the mid 20th century due to the combined impacts of DDT and other pesticides, extensive habitat loss and disturbance, over-hunting and trapping, and declines in prey populations. Its dramatic recovery stands as a testament to the success of environmental regulations banning DDT and concerted captive breeding and reintroduction programs. The peregrine’s extinction and return illustrate how quickly human activities can threaten even widespread species, as well as our power to reverse declines if conservation actions are taken in time.
