(Inside Science Currents) — On the roof of a parking garage in downtown San Jose, California, a spotting scope balances on a tripod, its lens pointed across the street at the roof of City Hall. Far above the blaring horns and ambulance sirens, a female peregrine falcon named Clara swoops silently toward City Hall with a pigeon dangling from her talons.
John Lewis adjusts the focus for a clearer view. He watches Clara toss gray feathers in the air as she prepares lunch for her young. John rushes to join fellow birder Jody Vandeveer at her laptop to make sure the three juveniles are still there.
Every May, fledgling falcons take flight from the nest at San Jose City Hall under constant human surveillance. From sunrise to sunset, John, Jody and dozens more volunteers track the birds, always ready to rescue any of the new flyers if they fall into the street.
The annual monitoring marathon, called Fledge Watch, was started by Glenn Stewart, director of the Santa Cruz Predatory Bird Research Group, an organization that tracks peregrine falcon movement and monitors up to 30 nests throughout the San Francisco Bay Area each year. Stewart modeled the event on the work the group did to help save the species from extinction in California in the 1970s.
"I took that experience and transferred it into an urban setting where members of the public can come and be of use to help the babies," Stewart said of saving fallen falcons. "We put them in a box, we take them in the elevator, and we go up to the roof of City Hall, and we release them up there."
He joined the research group in 1976 when California's peregrines were all but extinct. Widespread use of the insecticide DDT had contaminated the environment and caused mothers to lay thin-shelled eggs that crushed under their weight.
Stewart and other researchers snuck into nests, swapped the weak eggs with dummy eggs, and bred birds born from those eggs in captivity at the University of California, Santa Cruz. Once hatched, the healthy chicks were put into the nests. He and others helped bring back the birds from just two pairs in 1970 to around 300 pairs today, said Stewart.
In the wild, falcons choose tall cliffs for their nests. As populations began to move into cities, many pairs chose to raise their young in buildings. Cities offer pigeons for prey and Internet access for live streaming. Stewart's group set up webcams on the nests of popular peregrine pairs all over the Bay Area.
In 2005, the San Francisco Chronicle published a photo above the fold of a pair nesting on the Pacific Gas and Electric Company building in the city. The article included a link to Stewart’s website with the webcams. As the public got hooked, a new generation of people became invested in the peregrines' survival. The result was an extraordinary citizen science effort in which volunteers do more than simply monitor webcams — they actually contribute to Stewart's research.
"They send me information whenever they see banded peregrines," Stewart said.
Thanks to the volunteers who have joined his flock, Stewart can track peregrines' movements across multiple generations, giving a wealth of information he never would have gotten otherwise.
Lisa Marie Potter is a science writer based in San Francisco, California. She tweets at @Lisa_M_Potter.