Greased lightning

Peregrine falcons in California

Comback Kid - Photo: Glenn Stewart/SCPBRG

by Glenn Stewart

I was still five minutes from my observation point when I heard the unmistakable wailing call of a peregrine falcon. It was the unhurried, ascending wail, waaaaa, waaaaa, of the male as he let the female know that he was nearby as she lay atop her clutch of eggs.

I hurried along the trail hauling the weight of a heavy tripod, 60-power scope, binoculars, and thermarest to the edge of the canyon. I set up and soon located the peregrine on the branch of a snag across the canyon. He was so far away that I could see his beak open before the sound of his wailing reached me. What a stunning sight! Black cap, white breast, and slate gray wing all visible in the morning light.

The peregrine is known to be the fastest animal on the planet. Near vertical dives in pursuit of prey often exceed 200 mph. Photo: David Gregoire/SCPBRG

Every three or four hours, the male peregrine visits the female at the nest to deliver food to her or to give her a break from incubation. This "nest exchange" is the only opportunity observers have to pinpoint the location of the actual nest ledge.

After a long wait, I was rewarded by the sight of the male dropping from his perch in an arcing dive that ended with his landing on a cliff ledge. He bowed forward with a "chupping" call, and disappeared. The female had already emerged and was in flight before the cliff. But I held on the spot where the male had disappeared and carefully noted nearby landmarks-a large, round, flat-faced rock and reddish stain near the ledge where the male disappeared. Then I sat back and enjoyed the female's flight. She circled in the sunshine seeming to enjoy spreading wings and tail to gain altitude. After two or three turns of the circle, her feet dropped and a large stream of excreta fell away. She flew some more and then perched in the morning sun to preen and stretch. Surely, I thought, she is on eggs.

Here is a species that has fascinated humankind throughout the ages. The peregrine is an extraordinarily efficient bird hunter that is known to be the fastest animal on the planet. Near vertical dives in pursuit of prey often exceed 200 miles per hour. "Peregrine" is Latin for "wanderer" or "foreigner." Some peregrines that breed in the high Arctic migrate as far as the high, central plains of Argentina for the winter.

This magnificent bird almost became extinct because the pesticide DDT was causing eggshell thinning and breakage. By 1970, no peregrine falcons could be found nesting successfully east of the Mississippi River, and just two pairs were found producing young in California.

Peregrines nest in the sand and gravel found on protected ledges. Photo: Craig Himmelwright/SCPBRG

Thanks to the elimination of most uses of DDT and population recovery through captive breeding, releases of young, and, management of wild pairs, the species has recovered and been removed from the federal endangered species list. (The state of California continues to list the peregrine as "endangered.")

The nest in the Santa Cruz Mountains is one that I found while hiking several years ago. It is one of 12 to 15 such nest sites in the Santa Cruz, Monterey, San Benito, tri-county area.

Never in the past 50 years have peregrine falcons been more abundant. It is only during the approximately 100-day breeding period (courtship to fledging) that we can learn something about the California peregrine falcon population by counting nesting pairs and, if possible, noting the number of young. A database of this information has been maintained year after year since the early 1970s.

We monitor their numbers because fluctuations in the peregrine falcon population can be a valuable indicator of environmental health. Site fidelity is very high among this species, so many observers return to sites year after year to report on occupancy and productivity. With the current estimated California population at 300 pairs, Predatory Bird Research Group biologists cannot begin to monitor all of them within the breeding cycle, so we depend on the reports of volunteer observers.

The peregrine falcon is among the most widely distributed birds in the world nesting on every continent and major landmass except Antarctica. They nest in the sand or gravel found on protected ledges and prefer tall cliffs (and buildings and bridges) overlooking sea coasts, lakes, and rivers. Many people in the Monterey area are familiar with the "Embassy Suites" peregrines that perch on the building's letters from October to April each year. Like other wintering peregrines in the Bay Area, they disappear around the income tax deadline to return to their nesting territory which is likely somewhere in the Arctic.

The "Embassy Suites" falcons are sometimes seen standing on the ventilation stacks of the Monterey Bay Aquarium. In Santa Cruz, a wintering peregrine is often seen perched near the mouth of the San Lorenzo River or across from the Natural History Museum.

Glenn Stewart is Program Manager for the UCSC Predatory Bird Research Group.

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