LB6. Field Trip: Predatory Bird Research Group

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The Predatory Bird Research Group is located at the
Long Marine Lab of the University of California, Santa Cruz in California.

This story combines mystery, high adventure, and camaraderie, all dedicated to a creature of sky and cliffs. In the 1970’s, a small team of California biologists set out to save the western peregrine falcon from what looked like certain extinction. There were only a few breeding pairs left in the state and the birds were almost gone from North America.

Peregrin falcon in flight
Falco peregrinus (Peregrin falcon). Photo from the Predatory Bird Research Group.
Peregrines are the world’s fastest animals with flight speeds over 15,000 mph.
They can catch prey birds in mid-air.

As I searched for the temporary portable office at the edge of the University of Santa Cruz campus in 1999, I felt excited about this opportunity to learn from scientists who have studied falcons for more than twenty years. 

Brian Walton and a peregrin falcon
Falco peregrinus and Brian J. Walton of the Predatory Bird Research Group. Photo from the Predatory Bird Research Group.

Brian Walton, who coordinates the Predatory Bird Research Group (PBRG) described how he became hooked on peregrine falcons at an early age. “I went to Aviation High School near the Los Angeles Airport. Our mascot was the falcon…As fate would have it, I was assigned a term paper in the ninth grade that required research on falcons… When I graduated from high school there was only one pair of peregrines known to nest in California. The nest was on Morro Rock, so I moved there and enrolled in the local college.”

A chance meeting at Morro Rock in 1973, with ornithologist (person who studies birds) Tom Cade, encouraged Brian at age 22 to begin his career in falcon restoration research. Professor Cade had established a breeding colony of peregrines at Cornell University in New York and was working to increase peregrine research and restoration efforts. With the backing of the late Professor Kenneth Norris at UC Santa Cruz, and veterinarian James Roush, the Santa Cruz Predatory Bird Research Group was born.

Brian recalled the pressure in the early days to find answers to practical questions such as best hatching temperature and rearing conditions. At first, peregrine eggs were hatched at his home in hand crafted incubators set up in bureau drawers. So few birds remained in the wild that every egg was precious.

Peregrin falcon closeup
Falco peregrinus.
Photo from the Predatory Bird Research Group.

A breeding program was also underway in Boise, Idaho, and the researchers shared information and birds as they developed methods of hatching, rearing, and releasing young peregrines back into the wild.

A message that Brian has shared whenever he has the opportunity to talk with young people is how a few people who are knowledgeable and persistent can really change the chances of a species’ survival. “Where there is a will there is a way,” he commented, while describing how teamwork brought the peregrine back from near extinction.

I. The Mystery of Silent Spring

The research efforts that paved the way for the peregrine breeding programs began in the 1950’s when scientists like Tom Cade wondered why bird populations were in decline. Old newsreels from the 1940’s show tanker trucks traveling through neighborhoods and parks spraying DDT on lawns and ponds to wipe out mosquitoes. Health officials hailed DDT as an amazing new chemical that didn’t seem to harm large animals, but was very effective in killing insects.

person spraying DDT
Spraying DDT to kill mosquitoes as part of the 1958 U.S. National Malaria Eradication Program.  
Photo via Wikimedia Commons 

By the 1950’s DDT was being used throughout the tropical regions of the world in an attempt to wipe out malaria and other mosquito-born diseases.

Rachel Carson was among the first scientists to alert the public to the worldwide decline in bird species and other wildlife. Her careful reviews of field and laboratory research implicating DDT were presented in her book Silent Spring, published in 1962. At first she was belittled as a “nature nut,” and “bird watcher” by the chemical industry, food companies, and some government agencies, but soon her hypotheses were vindicated by the growing body of research evidence.

In following years, DDT and eleven other chemical pesticides Carson warned about were banned or tightly restricted. Extensive laboratory and field research revealed how DDT affects organisms, and how it is transported through the food web of ecosystems to cause declines in wildlife populations. Brian Walton read Silent Spring in high school and became a biologist so he could keep looking for peregrines.

Scientists documented that birds migrating to the southern US, Central and South America during the winter were feeding on grains and insects that had been sprayed with DDT. The DDT was converted to DDE, which binds readily with fatty tissue and remains in the body until the fat reserves are used by the animal. Birds that were stressed during migration often died when their bodies converted the fat, releasing the DDE.

Scientists also discovered that the low breeding success of many species of birds was due to DDT. The pesticide was found to cause eggshell thinning in peregrine falcons and many other predatory birds such as brown pelicans, bald eagles, and osprey. Bird predators that fed on contaminated wildlife were accumulating large doses of DDE. Accumulation of DDE in the fatty tissues disrupted calcium metabolism and caused thin-shelled eggs that often broke as the parent sat on the nest.II. Return of the Peregrine Falcon

August 20, 1999, this champion sky diver was down listed from the Endangered Species List, to a threatened species, its numbers in California at more than 150 breeding pairs. Brian Walton pointed out that the success story was the result of the dedicated teamwork of hundreds of scientists and private citizens who performed a variety of tasks that ranged from rock climbing to analysis of egg shells and tissue samples. 

Information and successes were generously shared between the three peregrine breeding centers located at New York, Idaho, and California. Captive birds were donated as breeders, and citizens who maintained guardian watches on wild nest sites contributed thousands of volunteer hours.

III. Pathway to a Career

Janet Linthicum
Janet Linthicum
Photo from the Predatory Research Group

Janet Linthicum reminisced about her first year on the job with PBRG. She was a self-proclaimed science geek in high school, mainly interested in chemistry and physics. As a freshman at UC Santa Cruz, she especially liked her wildlife biology course by Professor Todd Newberry, and decided to apply to Brian Walton’s ad for a Peregrine Nest Site Assistant. 

Her job description stipulated long hours, rigorous conditions, risk, and 11 months in the field each year, all for a tiny salary. She began work in 1983, in northern California as a nest guard, observing the birds, and protecting the nest from falconers. Camped alone in a tent, high on a bluff, she hauled water to her observation point. That spring, it rained constantly, and she read Fyodor Dostoyevsky’s novel, Brothers Karamazov, three times!

Despite many years of strenuous field work and laboratory research involved with incubating eggs in the lab, including night shifts, 7 days a week for 4-5 months at a time, Janet has never gotten over her love of peregrines, nor tired of seeing them in the wild.

The Predatory Research Group team
The PRG team
Photo from the Predatory Research Group

She commented that “wildlife biology and the concept of evolution has provided endless room to think about origins and to speculate.”

Her exciting career has enabled her to work throughout the west on population recovery efforts for peregrines, bald eagles, and the California Condor.

She has become a radio-telemetry specialist, and database specialist in the course of her work, and is co-author of the “Management Manual for Peregrine Falcons at the Eyrie”.

Janet is concerned that young people become interested in evolution and aware of the time involved for species and habitats to emerge. Often her free time is devoted to educating the public about the values of wildlife and habitat. “It seems wasteful to wipe out so many years of evolution for a temporary gain,” she points out.

On-Going Research Questions

The Santa Cruz Predatory Bird Research Group continues to expand its research efforts. Here are some of the current questions the scientists are investigating:

Falcon perched on a building
Falcon perched atop the Oracle Building.  
Photo from the Predatory Research Group

What factors influence how local and migrating bald eagles use California habitats? 

How effective are satellite telemetry transmitters in revealing the migratory patterns and habitat use of bald eagles?

How many burrowing owls nest in Santa Cruz and Santa Barbara counties and what are their habitat needs?

What factors influence golden eagle mortality from wind generators in the Altamont Pass Wind Resource area of California?

How can predation by peregrines on other endangered species like least terns, marbled murrelets, and snowy plovers be reduced?

How are environmental levels of DDT along the California coast affecting the breeding and survival of peregrines?

New Research Facilities

The many successes of the Predatory Bird Research Group (PBRG) resulted in a grant from the state to build a permanent “state of the art” facility at the Long Marine Lab, University of California, Santa Cruz. 

 At the PBRG’s web site,, you can find:

  • Current research on bald eagles, golden eagles, burrowing owls, Harris hawks, island foxes, seabirds, and of course peregrines.
  • Field techniques and biology behind the raptor research
  • Accomplishments of the research staff. 
  • the layout of this new research center 
  • Nestcams set up by PBRG
  • Bibliography of research articles and links to other major raptor research and education groups (The Peregrine Fund, the Raptor Center, the California Condor recovery effort)
Peregrin falcon in flight
Peregrine falcon photo by Elaine Miller Bond from article, 2014-04-29, in Berkeleyside: 
Friends in high places: Peregrine falcons soar above us

“Not long ago,  reader Patrick Hickey kindly sent in a photo of a beautiful bird of prey, perched on a tall building near his home in downtown Berkeley. 
…Rusty Scalf, teacher and trip leader for the Golden Gate Audubon Society, confirmed it: the bird was a peregrine falcon — the fastest animal on Earth. In California, not long ago, it was also one of the most endangered. 
…“Many of us were looking at the extinction of the peregrine in the 1970s,” said Glenn R. Stewart, director of the Santa Cruz Predatory Bird Research Group (SCPBRG) . “It really looked like they were going to be gone forever.” At that time, Stewart and other scientists could find only two pairs of peregrine falcons in California. In the eastern part of our country, peregrines were totally gone. 

…“The pesticide DDT — widely used in the 1940s, 50s, and 60s— accumulated in the fatty tissues of peregrine falcons (and also, bald eagles), causing these birds to lay thin-shelled eggs that broke in the nest during incubation. With the banning of DDT in 1972, and decades of impassioned work by Stewart and the SCPBRG, peregrine falcons have undergone a near-miraculous recovery.Today, an estimated 250 to 300 peregrine pairs are living and nesting in California, a number  that Stewart believes approximates original pre-DDT populations. “The interesting part of the peregrine’s tale is their adaptability to the urban environment,” says Shirley Doell…a peregrine volunteer — a “citizen scientist”— who ventures out at dawn nearly every morning in spring, plus some evenings, to monitor pairs of peregrines on skyscrapers, high-towered bridges, and tall industrial cranes in the East Bay. 

…“Most endangered species can only live in a particular niche in a particular kind of habitat,” Doell says. “But the peregrines don’t seem to mind the bustle and noise of the city, if there are tall structures and birds around for them to catch.” 

…In cities like Berkeley, Oakland, and San Francisco, peregrines hunt pigeons for about 90% of their diet. 

…“And living in a place like downtown San Francisco, where there’s an abundance of pigeons… it’s like living on a remote island in British Colombia with an abundance of sea birds nesting. Only here, the cliffs happen to be buildings, or bridges. The food happens to be nonnative pigeons.”…. 

By Elaine Miller Bond. Berkeleyside.

See also 

See Staying current for this chapter.