Mission Accomplished

by Tim Gallagher

In a last-ditch effort to rescue the American Peregrine Falcon, Cornell professor Tom Cade launched the most ambitious endangered species recovery program ever attempted. Now, nearly three decades later, this amazing bird is slated to be removed from the Endangered Species List.

Peregrine in front of Taughannock Falls
Like every other known Peregrine Falcon nest site in the eastern United States, this classic eyrie at Ithaca, New York's Taughannock Falls (photographed by Lab founder Arthur A. Allen in the 1930s) lay deserted after DDT devastated the falcon population in the 1950s.

The future could not have looked much bleaker for the American Peregrine Falcon (Falco peregrinus anatum) in 1970. Ravaged by the effects of DDT and other environmental contaminants, the falcon’s numbers had dwindled to the point that no nesting pairs had been found in the entire eastern United States for more than a decade. Lofty cliffs that had echoed with the cries of nesting peregrines for thousands of years before humans reached these shores stood quiet–like silent sentinels to the birds’ impending extinction. Even in places where civilization had not yet visibly encroached on their habitat, in the remotest reaches of the Rocky Mountains, the birds were vanishing, and many biologists feared the trend was irreversible.

But looking back now, it’s clear that 1970 was a crucial turning point for these critically endangered raptors–the year that Cornell professor Tom Cade initiated an aggressive, hands-on program to breed Peregrine Falcons in captivity and reintroduce them across the continent in areas where they were dwindling or already nonexistent. At that time, Cade, who was director of research at the Cornell Lab of Ornithology, formed an organization called The Peregrine Fund, dedicated to saving these rapidly vanishing birds. The group built a massive "Hawk Barn" at the edge of Sapsucker Woods Sanctuary to house the captive-breeding project. (Although the building remains, it no longer houses breeding falcons. The Cornell Raptor Program now uses the facility to breed accipiters–Goshawks, Cooper’s Hawks, and Sharp-shinned Hawks–and to house injured eagles and other birds of prey in need of rehabilitation.)

In its heyday, the Hawk Barn was a virtual Peregrine Falcon factory, where hundreds of young falcons were produced for release into the wild. What Cade and his army of falcon enthusiasts accomplished was incredible. They figured out how to breed large numbers of falcons in captivity and designed an effective reintroduction strategy. Eventually The Peregrine Fund and other collaborating groups released more than 6,000 Peregrine Falcons in 37 states and most Canadian provinces.

Perhaps the single factor that made the greatest difference in the Peregrine Falcon recovery was the vast number of people who were dedicated to the birds’ well-being. From the start, Cade had no problem attracting qualified staff and volunteers. Falcon enthusiasts from across the continent came forward to help. Many–including some of the key players in the recovery program, such as Cade himself, Bill Burnham (current president of The Peregrine Fund), and Jim Weaver (who ran the falcon breeding operation at Cornell)–were avid falconers with a deep, personal commitment to the peregrine. (Many falconers also donated their own birds to be used as breeders.) Others came from all walks of life and all income levels–bird watchers, business leaders, scientists, educators, public officials, naturalists, students. What they had in common was a profound passion for these birds and an inability to imagine a world without the Peregrine Falcon. What they accomplished was one of the greatest successes in the field of endangered species management.

Only seven miles from the Lab, Taughannock Falls was one of the first Peregrine Falcon reintroduction sites. Researchers built a shelf on the cliff and installed a long feeding pipe so food could be dropped to the ledge without the birds being able to see the humans who were feeding them.

Now, nearly three decades after the Peregrine Falcon recovery effort was launched, their accomplishment seems simple, almost predictable–produce thousands of falcons and release them across the country; the birds are bound to bounce back. But it’s always easy to be a Monday morning quarterback. In 1970, the whole enterprise was anything but sure. Although Peregrine Falcons had been trained and handled by falconers for centuries, they had never been truly domesticated. They always retained their aloofness–that air of nobility that ancient kings and aristocrats had so admired. And these birds had only been bred in captivity a handful of times before, most notably by ornithologist Heinz Meng, who had been a student of Lab founder Arthur Allen in the late 1940s and early 1950s.

Were these successful breedings a fluke? Many researchers thought so. They believed it would never be possible to breed massive numbers of peregrines in captivity. And even if you could, they reasoned, it would be impossible to release them successfully to the wild in numbers adequate to make a difference. The problem was that peregrines traditionally nested on lofty, rugged cliffs, performing grand courtship displays, rising and diving at scorching speeds across the open sky. No laboratory breeding facility in the world could duplicate these conditions. Would Peregrine Fund researchers be able to overcome these challenges? And, just as important, could they do it in time?

To understand the Peregrine Falcon’s dilemma and its ultimate solution it’s important to look back at the origins of the bird’s decline–the introduction of DDT into the environment in the late 1940s. The first inklings of trouble for the peregrines came soon after, but it was not until the 1960s that scientists learned the full scope of the catastrophe. Researchers discovered that the effects of DDT are cumulative, building up in the fatty tissue of small birds that consume contaminated insects. Peregrine Falcons, which exist at the pinnacle of the food chain, preyed on these birds and absorbed staggering amounts of concentrated DDT.

DDT inhibits the movement of calcium in a falcon’s system, causing the shell gland to produce eggs with shells sometimes 20 percent or more thinner than normal. The weight of a falcon as it brooded these fragile eggs was often enough to break the shells. And even if the thin-shelled eggs did not crack, many embryos perished due to an improper moisture or gas exchange through the shell.

The falcons were tracked using radiotelemetry (above). Below, Tom Cade (left) confers with Jim Weaver, who ran the falcon breeding operation at Cornell.

Proving that DDT was the culprit took a great deal of time and research. Cade had marked off an area along the Colville River in northern Alaska as a study site in the 1950s. He returned in the 1960s and began randomly sampling falcon eggs for pesticide contamination. Although the arctic peregrines on their breeding grounds were isolated from humans, their eggs contained high levels of DDT, apparently ingested during their long migrations to and from South America, where they winter. After comparing the pesticide levels in these eggs with the level in eggs taken in the lower 48 states, Cade predicted that the arctic peregrines would soon be in trouble.

His worst fears were realized three years later in 1969, when he found many non-nesting pairs and nests containing broken eggs or dead nestlings in his study area. The organs of the dead falcons had extremely high pesticide accumulations, and many of the eggs had significantly thinner shells than usual. Acting for a group of raptor biologists, Cade advised the Secretary of the Interior about the Peregrine Falcon’s dangerous situation. As a result, the bird was placed on the federal Endangered Species List in 1970. Cade’s research was also a major factor in the banning of DDT in 1972, which took a major effort by scientists, conservationists, and other concerned citizens.

When the captive-breeding program began in the early 1970s, Cade did not build massive flight cages for the peregrines to try to simulate natural conditions. Instead, he attempted to adapt the falcons to living in the breeding chambers constructed for them at Cornell. The birds were taken from wild nests at an early age–usually as down-covered chicks–and raised specifically to be breeders.

Prairie Falcon chicks were sometimes placed in peregrine nests after the birds' thin-shelled eggs were taken. The pairs readily accepted these chicks and raised them until incubator-hatched peregrines (above) could be returned to wild nests. Below, Phyllis Dague and Ron Walker replace a surrogate brood of Prairie Falcons with young peregrines. Manipulation of wild nests helped boost falcon numbers in areas that had a remnant population of Peregrine Falcons.

The researchers took many factors–including the falcons’ diet and the temperature and length of daylight in their natural environment–into account. They also conducted experiments with artificial insemination, which proved extremely useful with individual falcons that would not reproduce naturally.

Eventually the work paid off. In 1973, The Peregrine Fund produced its first captive-bred falcons–20 young peregrines. Once they had passed that milestone, the researchers lost no time in attempting to develop new techniques to boost falcon egg production. They experimented with a method called "double clutching"–taking the first clutch of eggs from a pair of falcons soon after they were laid. Egg collectors had long known that most birds would recycle and lay a second or even a third clutch of eggs if the first ones were destroyed or taken early in the breeding season. Peregrine Fund researchers found that this double-clutching technique worked well with peregrines, and it became a great boon to the falcon recovery program. It was especially valuable for rescuing some of the thin-shelled eggs laid by wild falcons. Many eggs that might have been lost through eggshell breakage or related problems were successfully hatched in specially humidified incubators.

"By 1975, we had produced enough falcons at our Cornell facility to take the next step–releasing young peregrines into the wild," says Cade. To accomplish this, Peregrine Fund researchers placed young both in traditional nest sites on cliffs and in "hack towers"–platforms built high above the ground in suitable areas where no natural nest sites existed. Because the young birds had no parents to feed and care for them, field assistants–most of whom were volunteers or received a small stipend–stayed with the birds for several weeks, monitoring their progress and providing fresh meat for them to eat. They avoided letting the young falcons see them when they left their daily rations, so the birds would not associate humans with food. After they fledged, the falcons would continue to stay near the release site and accept food until they had learned to hunt for themselves.

This release technique worked well for the most part, although in some locations, with no parents to protect them, the young falcons were sometimes killed by other predators. In wooded areas, Great Horned Owls were the single largest cause of death among the newly released falcons, accounting for about 50 percent of all losses in the eastern United States. In the West, Golden Eagles also killed many young peregrines. Some hack-site attendants had the harrowing experience of watching helplessly as young, inexperienced falcons were snatched by these powerful raptors and carried off to be eaten.

The Peregrine Fund built numerous "hack towers" (above), modeled after structures used for centuries by falconers, who believed that if young falcons had a chance to fly free (at "hack") for several weeks, it would speed their development as hunters. Falcons released by The Peregrine Fund were fed daily at these sites until they dispersed.

This was a bitter disappointment to The Peregrine Fund’s staff and volunteers, who had dreamed of quickly restoring the falcons to the great traditional eyrie cliffs of the East–such as the spectacular cliffs at Taughannock Falls here in Ithaca, where Arthur Allen took exquisite photographs of nesting falcons in the 1930s and 1940s. At Taughannock Falls, as in all too many other cliffside release sites in the East, the young peregrines quickly fell victim to the owls.

If you ask any of the staff and volunteers who took part in those early days of the release program if they ever had any doubts about the future success of the effort, they’ll invariably say no. Failure was unacceptable and, indeed, unimaginable. They just went back to the drawing board and tried again. To counteract the losses they were facing at the wild nest sites, The Peregrine Fund began releasing young falcons in urban areas, where Golden Eagles and Great Horned Owls would not be a significant threat to the birds.

"We decided to try urban releases because the young falcons would be relatively free from predators, and they would have a large supply of food in the form of feral pigeons and starlings," says Cade. "But cities are a mixed blessing. The birds sometimes have problems. They occasionally fly into reflective windows or get into other kinds of trouble. But people do get to see them. It calls attention to the problems of wildlife. The fact that these birds are in cities has created a lot of goodwill for the falcons."

The researchers also hoped that if enough falcons nested in cities to fill up all the available territories, some birds would eventually disperse away from urban areas and begin reoccupying traditional cliff sites (and this does appear to be taking place now in a number of areas).

And it was actually not unheard of even prior to the urban releases for Peregrine Falcons to nest on human-built structures. For centuries the birds have nested on castles in Spain and other areas, and a number of records already existed in the scientific literature of peregrines nesting on bridges and skyscrapers in North America–such as the famous pair that successfully raised young for several years on the Sun Life building in Montreal during the 1950s.

The great milestone year for The Peregrine Fund was 1980. That spring saw the first natural reproduction of Peregrine Falcons east of the Mississippi River in more than 20 years. Three nests produced six young. A modest start, but it was a clear indication of the enormous potential of the program.

The upward momentum of the peregrine recovery has continued to the present, with the known population of the American Peregrine Falcon increasing by 5 to 10 percent a year, even after the major release efforts stopped in the early 1990s. And no decline in the bird’s numbers has been detected in any region of the continent since 1980. The species’ numbers in North America have risen meteorically, going from a known breeding population across the continent (excluding Mexico) of 159 nesting pairs in 1975, when the releases began, to 1,650 nesting pairs in 1997, according to the U.S. Fish and Wildlife Service. And these are just the "known" pairs–many more undoubtedly exist. And now the Peregrine Falcon is slated to be removed from the federal Endangered Species List this summer.

It’s amazing to think back on the early days of the Peregrine Falcon recovery program and realize how much was accomplished in such a short time. More than anything else, the program is a remarkable example of what humans can do to counteract the negative effects our presence can have on natural ecosystems. Of course, with DDT being banned in the 1970s, it’s possible that the peregrines would eventually have come back on their own–although that is by no means certain. But it definitely would not have happened in our lifetimes or perhaps even in the lifetimes of our children.

Hundreds of Peregrine Falcons now nest across North America, from east to west and north to south, and we owe the presence of these birds to all of the dedicated people who took part in the recovery effort. A remarkable number of them changed the entire direction of their lives to help the peregrines. Some switched careers or took leaves from college just so they could take part. But I’ve never heard anyone say that they have any regrets.

As for The Peregrine Fund, the group closed its Cornell facility in the late 1980s as the falcon reintroduction program was nearing completion in the East, and it is now headquartered at its World Center for Birds of Prey in Boise, Idaho. Even though The Peregrine Fund’s flagship (and namesake) species has recovered, the group has plenty of other vital projects. Threatened raptor species from throughout the world–the California Condor, Mauritius Kestrel, Orange-breasted Falcon, Harpy Eagle, and more–are already being bred in captivity and released by the group to ensure their continued existence, using techniques pioneered with the Peregrine Falcon. And Peregrine Fund researchers have even branched out beyond birds of prey to guide recovery efforts for the ’Alala, the ’Oma’o, and other critically endangered Hawaiian forest birds. Clearly, they have plenty of work to carry them into the new millennium.

A grand celebration of the Peregrine Falcon’s recovery will take place this August 20—22 at the World Center for Birds of Prey in Boise, Idaho. Everyone involved in the restoration of the bird is invited to attend this special event, sponsored by The Peregrine Fund, the Santa Cruz Predatory Bird Research Group, and the Raptor Center at the University of Minnesota.

For more information, contact The Peregrine Fund, 566 West Flying Hawk Lane, Boise, Idaho 83207; phone: (208) 362-3716; FAX: (208) 362-2326; e-mail: tpf@peregrinefund.org.