Yosemite’s Peregrine Falcons Are Rebounding Thanks to Unlikely Allies: Rock Climbers

Long absent from Yosemite National Park, peregrine falcons are making a comeback with help from some unlikely allies: rock climbers.

Rock climbers and peregrine falcons could easily be at odds, since they both flock to the sheer granite cliffs of the 1,169-square-mile California park. The presence of climbers can disturb nesting falcons, and rock climbing is listed as a potential threat to the species. But instead, humans and birds have forged a unique partnership that has allowed peregrine falcons to flourish after decades of decline.

This week, the National Park Service and the Yosemite Conservancy provided an update on the peregrine falcon recovery within the park. In the spring of 2024, naturalists counted 17 breeding pairs—a nearly 113 percent increase from the eight pairs counted in 2009—as well as 15 nests and 25 chicks. Since 2009, 51 total nesting sites located within Yosemite have produced 385 baby birds.

“Peregrines are at the top of the food chain and the most susceptible to contamination,” says Frank Dean, president of Yosemite Conservancy, to the San Francisco Chronicle’s Sam Whiting. “So to have them bounce back to this degree is a sign of the health of the entire Yosemite ecosystem.”

Peregrine falcons are the world’s fastest animal, reaching speeds of up to 200 miles per hour when they dive from great heights to catch their prey. These majestic birds live on every continent except Antarctica, seeking out rocky cliffs to build their nests and raise their young.

Once abundant around the world, their numbers began to dwindle after World War II because of the use of pesticides like dieldrin, aldrin and DDT (dichloro-diphenyl-trichloroethane). Dieldrin and aldrin are toxic and killed the birds outright, while DDT weakened chicks’ eggshells, lowering their odds of survival.

In the United States, the falcons’ numbers reached a low point of 324 pairs in 1974—a massive decline from the more than 3,800 pairs counted before the mid-20th century. Peregrine falcons were placed on the federal endangered species list in 1970 and on California’s endangered species list in 1971.

In Yosemite, the birds disappeared entirely: The last known pair at the time had been seen in 1941.

The U.S. Environmental Protection Agency (EPA) banned the use of DDT in 1972. Two years later, the agency banned most uses of aldrin and dieldrin, with an exception for termite control. (In 1987, the agency banned all uses of the chemicals.)

Not long after the bans took effect, Dale Bard, Hugh Burton, Bruce Hawkins and Ron Kauk made a startling discovery while climbing the southeast face of Yosemite’s El Capitan in 1978: an active peregrine falcon nest.

The athletes reported their find to conservationists, who quickly sprang into action. They came up with an ambitious plan—and asked the climbers if they wanted to help.

At the behest of the Santa Cruz Predatory Bird Research Group, climbers once again scaled El Capitan writes the Mercury News’ Lisa M. Krieger—but this time, they collected samples of eggshells from the nest and brought them back down for testing.

The eggs were delicate and thin, so researchers decided the best course of action was to incubate them in a laboratory, then return the hatchlings to the nest. Rock climbers helped with this, too, much to the chagrin of the protective peregrine falcon parents: As the climbers carefully removed eggs or replaced chicks, the falcons dive-bombed them—one bird even struck a climber’s backpack.

“Just when I thought I was going to die, they would flare their wings above my neck and glide off, just inches from me,” says Ken Yager, one of the climbers who helped with the efforts and the founder of the Yosemite Climbing Association, to the Mercury News.

Yager’s story illustrates how climbers were willing to “risk all” to help the birds, as Rob Roy Ramey II, a biologist and climber who helped with the project, told Outside’s Ula Chrobak in 2018.

In addition, for the last 15 years, climbers and the park service have teamed up to help protect the birds through the Peregrine Falcon Protection Program. From March through July, the park implements temporary, rolling closures of climbing routes as the birds return to their nest sites, lay eggs and rear their babies. They’ve also created buffer zones to prevent helicopters from getting too close.

Park service staffers closely monitor the nesting sites and adjust the closures accordingly. At any given time, more than 95 percent of the park’s climbing routes are open, per the Mercury News.

The presence of humans and vehicles can alter the behaviors of many animal species, including falcons. Birds, in particular, have been known to leave their nests to defend against interlopers, making their eggs and chicks vulnerable to predators. (In New York this summer, territorial nesting shorebirds have been mobbing drones deployed to protect swimmers.)

Peregrine falcons were removed from the endangered species list in 1999. Population estimates vary, but as many as 40,000 individuals may now be soaring freely in North America, according to the American Bird Conservancy. Globally, Partners in Flight estimates there are now 340,000 peregrine falcons. The International Union for Conservation of Nature considers them a species of “least concern” and reports that their numbers are on the rise.

Without the cooperation of climbers, peregrine falcons might still be struggling to gain a foothold in Yosemite. Instead, the birds’ recovery is a rare success story of humans prioritizing the needs of other species above their own.

“It’s a remarkable comeback with new discoveries resulting from a collaborative strategy,” says Alexandria Walker, a biological science technician for the national park, to Fox26’s Liam Cavaletto.

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Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.