I used to think extinction was something that just happened—like a switch flipping off in the dark.
But here’s the thing: the peregrine falcon’s near-disappearance in the 1960s wasn’t some mysterious evolutionary dead-end. It was us. Specifically, it was dichlorodiphenyltrichloroethane—DDT, that miracle pesticide we sprayed across millions of acres of farmland starting in the 1940s. The chemical didn’t kill adult falcons outright, which might’ve been kinder, honestly. Instead, it biomagnified up the food chain: insects absorbed it, small birds ate the insects, falcons ate those birds, and the DDT metabolite DDE accumulated in their tissues. The result? Eggshells so thin they crumbled under the weight of incubating parents. By 1970, peregrine populations in the eastern United States had dropped to exactly zero breeding pairs. Zero. In the West, maybe a couple dozen hung on in remote cliff faces, but ornithologists were already writing obituaries.
Then Rachel Carson published Silent Spring in 1962, and people started paying attention. The EPA banned DDT in 1972, which feels fast by today’s regulatory standards, but it still took a decade of political fighting.
The Chemistry Behind the Catastrophe That Almost Worked Permanently
DDT breaks down into DDE in animal bodies, and DDE interferes with calcium metabolism—specifically, it disrupts the enzyme carbonic anhydrase, which birds need to deposit calcium carbonate in eggshells. I’ve seen museum specimens from that era: shells so fragile they look like tissue paper. Some were literally half the normal thickness, around 0.2 millimeters instead of the usual 0.4. Researchers at Cornell’s Lab of Ornithology measured this obsessively, collecting thousands of broken eggs from nests. The data was grimly consistent: the higher the DDE concentration in the mother’s body, the thinner the shell. It wasn’t subtle. It was a mechanical failure at a molecular level, and it was happening across dozens of raptor species—ospreys, bald eagles, Cooper’s hawks. But peregrines, being apex predators with high metabolic rates, got hit hardest.
Anyway, the ban alone wasn’t enough to bring them back.
Captive Breeding Programs and the Unglamorous Work of Reintroduction Science
Tom Cade, a falconer and ornithologist at Cornell, started the Peregrine Fund in 1970 with a straightforward idea: breed falcons in captivity and release them into the wild. Sounds simple. It wasn’t. Peregrines don’t breed easily in cages—they’re territorial, skittish, and require specific nesting conditions. Cade’s team used a technique called “hacking,” where young birds were placed in artificial nest boxes on cliffs or buildings, fed remotely until they fledged, then left to fend for themselves. Between 1974 and 1997, the Peregrine Fund and partner organizations released more than 6,000 captive-bred falcons across North America. The mortality rate was high—maybe 60% didn’t survive the first year—but enough made it. By the mid-1980s, wild breeding pairs started appearing in places they’d been extinct for decades: New York City skyscrapers, bridges in San Francisco, the cliffs of Yosemite.
I guess it makes sense that a bird adapted to hunt pigeons in open skies would thrive in urban canyons.
Why the Recovery Worked When So Many Conservation Efforts Fail
The peregrine’s comeback wasn’t just luck or good timing—it was a combination of regulatory action, scientific rigor, and ecological flexibility. DDT levels in North American ecosystems dropped roughly 80% within a decade of the ban, which gave the reintroduced populations a fighting chance. Falcons also benefited from their adaptability: they nested on bridges, power plants, and office towers, exploiting habitats humans had created. By 1999, the U.S. Fish and Wildlife Service removed the peregrine falcon from the Endangered Species List. Today, there are an estimated 3,000 to 4,000 breeding pairs in North America, compared to maybe 10% of that in 1970. It’s one of conservation’s genuine success stories, though I sometimes wonder if we celebrate it too much—like we’re patting ourselves on the back for fixing a disaster we caused in the first place. Still, it proves recovery is possible when we actually stop poisoning things and commit resources to repair. The falcons didn’t save themselves, but they definately didn’t give up either.
