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Helicopters and California Peregrines

Navy helicopter delivering young to San Miguel IslandAs a natural historian, I prefer to sit quietly and observe peregrines with binoculars from a distance. As a population or conservation biologist, I needed to find peregrines and obtain information over a large area. The nature of peregrine occupancy within its range caused problems. First, they are widespread. Second, when we started our work they were extremely rare. Third, they nest on cliffs that can be very extensive in terms of width, and occasionally height. The use of helicopters was a partial problem solver for us in our work here in California.


Many of the places where we were seeking to find information about peregrines were remote. Sometimes we were interested in finding birds in wilderness, National Parks, refuges, or National Forests. Some people wondered if the helicopter, often forbidden or restricted for use in these areas, was the appropriate tool for the job. And was not the peregrine in those areas likely to be secretive or shy and easily disturbed?

The answer is that depending on the skill of the pilot, and the knowledge of the biologist flying with the pilot, helicopters can be either valuable or a disturbance. On one occasion many years ago I had the good fortune to go to New York City and make a presentation before a major corporation considering funding our endangered species efforts. They provided me with a plane ticket and then a ride from JFK airport to the downtown Manhattan Island headquarters area in their corporate helicopter. It was evening and the flight along the rivers, over famous bridges, and between skyscrapers was a real treat. Another passenger on the flight was a lady who had never flown in a helicopter previously. She was terrified to be flying amongst the towering buildings. She was sure that we would crash into one. Being the "experienced" passenger I tried to console her by relating how I had flown very near cliffs surveying birds and I told her I was positive it was perfectly safe. That did little for her nerves. The pilot finally came on the radio and explained that he had learned to fly in Viet Nam, had been shot down twice, and had helped evacuate Saigon. He convinced her that he could handle that particular situation safely. Often we have heard that same story from pilots who have helped us with surveys. The skill of the average helicopter pilot in the 1970s was honed in war. Our worries only needed to be in finding falcons, not in pilot skill.

These pilots would ask us for information on the biology of the bird, and then adapt their knowledge to accommodate our needs. We knew that falcons did not like sudden loud noises. We knew the top of the cliff is a sensitive area for falcons. We needed to see the small crow-sized birds before they could slip away if they were aware of our approach. We worked together and found that if suitable cliffs were approached in a perpendicular pattern (approached at a right angle from several hundred yards in front of the cliff), at approximately the level of nest ledges the falcons would not flush and we could close in and actually determine if the cliff was occupied.

People automatically assume that the peregrine is afraid of modern flying machines and understands and fears the danger of the rotors. This is actually untrue. Over the past few thousand years as the species evolved, no mechanical flying machines were present to enter into the process that resulted in instinctive behavior in falcons. The present day falcons can not learn that a rotor is dangerous. Any strikes would simply mean death, not a learning experience. As a result the falcons are fearless of the helicopter. A loud noise or something bursting over the top of their nest cliff might flush nesting birds. A slow deliberate approach from the front of the cliff is tolerated. The approach is allowed so close that nesting falcons will remain on their nests even if the helicopter is close enough (<30 feet) that their loose breast and back feathers blow about in the rotor wash. That closeness is not necessary and was only observed in extraordinary instances, but it shows the ability of the pilots to fly safely and the falcons to tolerate this tool. Used properly by skilled workers, the helicopter proved to be invaluable in determining the status of the peregrine in California. Several of the people at SCPBRG have had entirely different experiences with other species of birds, so what I describe here applies to peregrines, but not, for example, eagles or many other species of birds.


Helicopter in the fieldFor many years in most of California the helicopter was primarily used to confirm that the peregrine was extremely rare and that most territories were vacant. Skeptics suggested that we were simply not skilled enough to find birds. They believed peregrines were actually living secretly in remote areas all along. It is true that peregrines are difficult to find and certainly all biologists would confirm that a trip to a new territory could result in birds being missed. The helicopter is a valuable tool in surveying territories where nest ledges are known and can even be used to determine productivity by a skilled biologist. Dr. Monte Kirven probably holds all the unofficial "records" for peregrine work in California such as most territories visited by helicopter, most territories visited on a single day, most baby peregrines seen a on single day, etc. I am confident that he would acknowledge that some birds in territory surveys were missed. But when survey routes of Sandy Boyce, Clayton White, James Enderson, Carl Thelander, Lloyd Kiff, Geoff Monk, and other "old-timers" are revisited now that peregrine recovery has occurred, it is quite common to see peregrines where they saw none. Certainly all of the nesting falcons are not seen, and there is nothing like a good biologist with a day in the field with binoculars to determine what exactly is occurring. Future surveys may require helicopter use because California is so large, the back country is so remote, and peregrine numbers are now so large that no other state-wide survey method is feasible on an annual basis.

The helicopter is a treat for biologists also since it can give you a glimpse at what the peregrine’s life is like. Unlike many birds that are terrain oriented, peregrines live in the air. For that reason they can live on prominent geological features on islands, in forests, along rivers, or in cities on bridges and buildings. They hunt in the air. From a helicopter a biologist can truly appreciate nest ledge selection, orientation of nests to hunting areas, wind resources available to the falcons, and other similar parameters of the territory. A biologist viewing the cliff from afar with binoculars can not gain that perspective. Also the speed and maneuverability of the helicopter itself can crudely simulate the flight of the falcon. I will never forget the feeling of flying rapidly 50 feet over the terrain and short trees in Yosemite National Park, only to come to the top of a vacant 3000-foot nesting cliff and burst over the edge. The ground went from 50 to 3050 feet below me in a moment. Recently on the Channel Islands, we encountered a peregrine soaring over the east end of San Miguel Island at approximately 400 feet above the terrain. We hovered nearby and after a few minutes the bird, a female, flew in a southwesterly direction. We followed along at a distance of about 200 yards off its left wing for 8 minutes. It was flying at 70 miles per hour, and it appeared to be cruising. We had to turn back, but we hovered for a few more minutes while the bird flew out of sight out over the Pacific Ocean.

Helicopters can fly as the "crow flys" and this makes territory visits simple and economical. It also allows for determination of densities, and more importantly helping to understand the nature of the occupation of habitat. Spatial orientation of cliffs, distances between pairs, and locations of hunting areas are extremely difficult to interpret from the ground or via maps. Once again, it is the closest thing to a peregrine eye view of the habitat that the modern biologist can employ.

One drawback is that the helicopter itself as a machine is potentially dangerous. There have been instances with other biologists where defensive nesting birds of various species have attacked the helicopter and been killed. We have never had a close call in California. We have lost a few close friends in helicopter crashes, and fortunately one close colleague, Dick Anderson of the California Energy Commission, survived a crash. In the peregrine work, other than Monte Kirven who seems to encounter close calls with death more than most of the rest of us, we have never had any close calls with helicopter malfunction or pilot error. Personally I have paid my dues and feel that it is time for other people to conduct future peregrine surveys, but I value and enjoyed my experiences and believe there is a place in the future for this tool to continue in peregrine falcon recovery and research efforts.

Helicopter Transporting a Hack Box to a Remote LocationHelicopters have been used as a tool in many other aspects of our programs as well. Biologists can be dropped off or picked up in remote places that would require too much time to allow for observation if a multi-day pack trip was required. A crucial use for the helicopter has been the delivery of hack boxes to remote release locations. Even more importantly was the actual placement of the box on cliff ledges or rocks that would be otherwise inaccessible to a team of biologists attempting to manually carry the box into a difficult position. Finally, when the nestlings are delivered to remote nest sites for fostering into nests, and on some occasions when the fledglings are delivered to hack boxes for release, the helicopter has enabled releases in difficult locations or during adverse weather that made such releases safe for the young falcons. This tool has been essential to the recovery program and program feasibility and economy have been enhanced. We also had some fun and excitement at the same time so overall we welcome the appropriate use of this technology in the sensitive biological work with endangered species in California.


Steve Herman conducted the first peregrine surveys in the post-DDT related decline era in 1970. Herman (then a professor at UC Santa Barbara and later at The Evergreen State University) traveled mostly by automobile around the state, stopping at historical cliffs and observing with binoculars. Later Carl Thelander (then a graduate student at San Jose State University and now a private consultant) used similar techniques on subsequent surveys in the mid 1970s. Both of these researchers were limited by access via roads or short hikes. The state of California is very large for a single season survey of all historical territories. Vast regions of the state were uncharted areas where the historical population was never documented. Beginning in the later 1970s and continuing into the 1980s the state was explored by helicopter in an attempt to understand available cliff habitat and locate remaining occupied nest cliffs. I made many trips to the Channel Islands in the 1970s and 1980s. Sandy Boyce (then a graduate student at Humboldt State University and now a raptor biologist for the US Forest Service), Clayton White (a professor at Brigham Young University), and James Enderson (a professor at The Colorado College), conducted widespread surveys of US Forest Service lands. They made many flights in the northwestern portion of California and in the Sierra Nevada. Carl Thelander, Lloyd Kiff (curator of the Western Foundation of Vertebrate Zoology) and myself conducted surveys of US Forest Service lands in the Transverse Range of central, coastal California in the early 1980s. Also, in the 1980s I surveyed all river drainages from the Pit River in the Cascades to the Kern River in the southern Sierra Nevada. Other than the northwestern California surveys, virtually no peregrines were observed on any of these flights. Cliffs where hundreds of pairs had nested prior to DDT’s first use in the mid-1940s were virtually all vacant in the 1970s. Clearly the helicopter was essential in documenting the extent of the decline of the peregrine falcon in California.

Geoff Monk (then a graduate student at UC Berkeley and now a private consultant) added to the surveys of northwestern California where some peregrine cliffs were found occupied. He and is co-worker and successor Monte Kirven (now a private consultant) logged hundreds of hours of helicopter surveys in the early to late 1980s. They surveyed habitat and later documented occupancy and productivity for cliffs north of San Francisco in the Coast Ranges, across the northern boundary of the state into the Cascades, and then south in the Sierra Nevada to the American River canyon area. Kirven undoubtedly has logged the most hours of helicopter work in the history of the California peregrine survey.

I continued to opportunistically survey habitat throughout the state in the late 1980s. Flights were continued to the Channel Islands, individual surveys were made of the Colorado River region, the San Gabriel, San Bernardino and San Jacinto Mountains, and selective surveys were occasionally conducted in the Cascades and Sierra Nevada Mountains. In the 1990s only the Channel Islands received any coverage via helicopter, usually by myself, and that was sporadic.


The initial surveys of Boyce, White, and Enderson and also Thelander, Kiff and myself were largely funded by the US Forest Service in a program set up by Dean Carrier and Harley Grieman of that agency. The work of Monk and Kirven was funded largely by the BLM through a program set-up by Richard Olendorff and Paul Yull. Additional funds were occasionally provided by the US Forest Service and/or the US Fish and Wildlife Service. Co-operating businesses and agencies donated virtually all flights undertaken by personnel of the SCPBRG. Over the years we have been accommodated by the US Navy, Marines, Air Force, and Coast Guard; the California Highway Patrol, National Guard, and Department of Forestry; the Pacific Gas and Electric Company, Southern California Edison, various television stations, oil companies, and timber companies. A large number of organizations have helped with our efforts to reach cliffs in areas of their jurisdiction or interest.

-Brian J. Walton