Flying Back from the Brink
by David Salvesen
Circling high above the Hudson River, a lone peregrine falcon silently scans the landscape below. Herring gulls scavenge for floating scraps. A great blue heron skirts the water's edge for small fry. The falcon's coal-black eyes, however, fix on an unwary pigeon recklessly crossing the river. The hunter tucks its wings close to its body and plummets toward its target, soon reaching 100 miles per hour. Special baffles in its nostrils slow incoming air, allowing the falcon to breathe during its rapid descent. Within seconds, the falcon slams into the hapless pigeon in an explosion of feathers. Then, with its prey grasped in its sharp talons, it heads for a perch on the George Washington Bridge. This is no wilderness raptor, but one of many peregrine falcons that now call urban America home.
Just 30 years ago, the peregrine falcon was on the brink of extinction, a victim of contamination by DDT, an agricultural pesticide used widely following World War II until it was banned in 1972. DDT worked its way up the food chain with dire consequences for falcons, eagles, and other birds of prey. By the early 1960s, the number of peregrines had fallen precipitously. East of the Rocky Mountains, the species was essentially wiped out. A survey in 1964 failed to find a single occupied peregrine nest east of the Rockies, while in the west, peregrine populations had fallen by over 70 percent.
Since the 1970s, the peregrine has made a remarkable comeback, due primarily to the ban on DDT and the release of nearly 5,000 young peregrine falcons that were bred and raised in institutions and zoos. Peregrines can be seen once again in wild areas and also in cities, including Chicago, Milwaukee, New York, Philadelphia, Cleveland, Wilmington, Baltimore, and Washington, D.C.
"It's a real success story," remarks William Burnham, President of The Peregrine Fund, a private, nonprofit organization that operates the World Center for Birds of Prey in Boise, Idaho. The Fund has raised peregrine falcons, aplomado falcons (see Return of the Aplomado Falcon) and, more recently, California condors for release into the wild. It has ten pairs of California condors that it will breed for ultimate release in the Grand Canyon. But by far The Peregrine Fund's biggest accomplishment since the mid-1970s has been the release of more than 4,000 captive-bred peregrine falcons in 28 states. Other U.S. groups that have released peregrines include the Predatory Bird Research Center (more than 700 falcons) in Santa Cruz, California, and The Raptor Center (more than 700 falcons) in Saint Paul, Minnesota. Also, some falcons were released by Cornell's Laboratory of Ornithology in the early 1970s, before The Peregrine Fund moved to Idaho, and by organizations in Canada.
Cheetah of the Sky
Found on all continents except Antarctica, the peregrine falcon is one of the most widely distributed species on earth. It occurs from the Arctic to Patagonia, throughout Europe, Asia, Africa, and most of Australia. Three subspecies of peregrine falcon occur in North America: the American peregrine (Falco peregrinus anatum), which breeds throughout most of North America, and migrates to Mexico and occasionally into Central America; the Peale's peregrine (Falco peregrinus pealoi), which inhabits the northwestern U.S. and adjacent parts of Canada; and the Arctic peregrine (Falco peregrinus tundrius), which breeds in northern Canada and migrates to South America as far south as Patagonia.
The peregrine falcon is capable of diving speeds of over 100 miles per hour, although some claim that when diving it can reach over 200 miles per hour. According to Dr. Pat Redig, director of The Raptor Center at the University of Minnesota, "There's a lot of myth about how fast a peregrine can dive. I tend to believe a falcon's top speed is about 100 to 120 miles per hour." About the size of a large crow, the peregrine preys mostly on small birds in flight, but has been known to bring down ducks and pheasants. According to Robert Mesta, wildlife biologist with the U.S. Fish & Wildlife Service's (USFWS) Ecological Field Office in Ventura, California, "The peregrine likes its prey to be alive and moving, although it will occasionally take birds perched on the ground." Smaller birds usually are killed on impact. Larger birds, however, typically are stunned by the high-speed collision and then brought to the ground where the peregrine finishes them off with a quick, well-placed strike to the back of the neck. A notch in the peregrine's hooked beak is specially adapted to break the neck of its prey.
Broken Shells and DDT
The decline of the peregrine falcon paralleled the increase in use of organochloride pesticides such as Dieldrin, Aldrin, and DDT during the 1950s and 1960s. The pernicious effect of these potent, and persistent, chemicals on birds of prey was not discovered until the late 1960s. As insects contaminated with organochlorides were eaten by birds, and these birds in turn were eaten by raptors, DDT worked its way up the food chain, accumulating in ever-higher concentrations in the tissues of species at the top of the chain. DDE, a metabolite of DDT, interfered with the peregrine's normal calcium deposition during the formation of eggshells, resulting in thinner shells that often broke during incubation. Falcons nesting in agricultural and forested areas where DDT use was high suffered greatly. In the eastern U.S., successful peregrine reproduction came to a halt and declined substantially throughout the world.
In 1973, the USFWS listed the peregrine falcon as an endangered species, one of the first species to be listed under the Endangered Species Act of 1973. The USFWS prepared recovery plans for different regions--Alaska, the Pacific coast, Canada, the Rocky Mountains, the eastern U.S., and Mexico--and set recovery goals (such as minimum number of nesting pairs and offspring, thickness of eggshells, and levels of organochlorides in eggshell) for each region.
In some areas, like Alaska and northwest Canada, enough falcons survived the DDT onslaught that populations recovered naturally, without the need for release of captive-bred birds. But in the east, the loss of peregrine falcons was so great that there simply were not enough around to easily repopulate their former haunts. So the release of captive-bred falcons was deemed necessary. "Eventually, the peregrine falcon would have recovered on its own, but the recovery wouldn't have been so dramatic or widespread without the release programs," surmises Mesta.
Hacking it in the Wild and in Cities
Falcons are the swiftest birds of prey. Like other members of its family, the peregrine's speed, strength, and aerial acrobatics have captivated people for centuries. Early Egyptians worshipped a falcon god called Horus. Centuries later, the Holy Roman Emperor, Russian czars, and kings in England and France all kept falcons for sport and prestige.
Falconry is thought to have originated in central Asia around 4,000 years ago and was introduced to Europe by Crusaders who brought back trained falcons from campaigns in the East. At the beginning of World War II, the British trained peregrine falcons to intercept Nazi carrier pigeons. Unfortunately, wild falcons did not distinguish between Nazi and Allied pigeons and subsequently, the falcons themselves became the target of attack by the British Air Ministry. During the war, hundreds of young and adult peregrine falcons on the south and east coasts of England and parts of Scotland and Northern Ireland were destroyed. After the war, the falcons quickly recovered, only to be hit soon after by DDT.
Today, falconry lives on in the U.S. and abroad. The North American Falconers Association, headquartered in Winifred, Montana, boasts about 2,500 members. It would be hard to overlook the crucial role played by falconers in the recovery of peregrine falcons. The original birds released from captive breeding programs were donated or sold by falconers. According to Ralph Rogers, past president of the North American Falconers Association and an active falcon breeder, "No one but a falconer had ever bred a falcon successfully before." Moreover, the release techniques had been developed over the centuries by falconers as well.
The preferred release method is called "hacking," in which four-week-old falcons are put into a four-foot-high, six-foot-wide, and eight-foot-long box, called a hack box, mounted along a cliff, or on a tower or tall building. Bars across the front of the box protect the fledgling falcons from predators while allowing them to see out. The babies, five to a box, are fed through a hole for a few weeks. Then the front of the cage is removed so the birds can learn to fly and hunt, while still being fed by caretakers, who remain out of sight. The entire process usually takes five weeks. Fostering is another method sometimes used, mainly in areas where eggshell thinning still occurs. Wild falcon eggs are exchanged for two- to three-week-old captive-bred chicks, which are sometimes preceded by dummy eggs that are swapped for the originals.
The breeding and release programs started in the early 1970s at the Laboratory of Ornithology at Cornell University, which spawned The Peregrine Fund. Other organizations, such as The Raptor Center and the Predatory Bird Research Center also were instrumental in the success of the program. Initially, several organizations expressed doubts about the release program because falconers were involved. Indeed, most of the people involved, including most of the members of the board of The Peregrine Fund, were falconers. Rogers, who refers to peregrine falcons as "charismatic megafauna," chaffs at the suggestion that falconers were involved only for self-interest. "I've raised quail in my bedroom to feed falcons to get them back on the cliffs again," he asserts.
Initial efforts at releasing captive-bred falcons, which included both fostering and hacking young, were largely unsuccessful, however. Most of the young falcons fell prey to great horned owls (Bubo virginianus), eagles, and other predators. "We released many peregrine falcons on the cliffs along the Mississippi River," recalls Dr. Redig, "but great horned owls got almost every one of them." In the east, peregrines suffered a similar fate. "Falcons released in the Appalachian Mountains, where falcons occurred historically, were being nailed by predators, particularly the great horned owl," echoes Craig Koppie, Mid-Atlantic Region Peregrine Coordinator with the USFWS Chesapeake Field Office in Annapolis, Maryland.
In response, the release programs moved to cities, which are relatively free of predators, have ledges for falcons to nest and roost on, and offer a ready supply of prey--pigeons. "Falcons like buildings better than cliffs," notes Redig. "There's plenty of prey and no predators. It's a better habitat." Several peregrine falcons released in the wild have moved to the cities on their own.
Starting in the late 1970s, peregrine falcons were released from tall buildings and bridges in numerous cities in the East and Midwest. Today, there are an estimated 100 pairs of peregrines nesting in 60 cities across the United States. In Washington, D.C., a half dozen peregrine falcons were released from both the Smithsonian Castle and the Department of Interior Building. The birds soon disappeared without a trace, except for one that was killed at National Airport. A pair nests at the National Shrine of the Immaculate Conception at Catholic University. In Baltimore, there are two pairs of falcons: one on the United States Fidelity and Guarantee (USFG) Building and another on the Francis Scott Key Bridge. A pair in Milwaukee, named Sibella and Bill, have raised 18 offspring in their six years there.
Falcons released in urban areas have been known to migrate to other cities. The female of the pair at Catholic University arrived from New York City. According to Koppie, a male and female born from different clutches on the USFG building have moved to the James River Bridge in Virginia and set up a nest. "They're very fertile and have produced four young each year for the last two years," observes Koppie. Another offspring from the USFG building was spotted in Toledo, Ohio. Peregrine falcons have also been released on man-made towers along the Atlantic coast with great success. Historically, peregrines did not live along the coast, which offered few cliffs or vantage points. Yet, falcons have in recent years adapted well to man-made accommodations. "If you're a falcon, you could hardly ask for a better location," remarks Koppie. "There are few predators, and the Atlantic coast is a major flyway for all sorts of birds. The falcons just wait for dinner to come to them," says Koppie.
Recovery: City Birds Lead the Way
Today, with peregrine falcons firmly established in dozens of cities and with many having successfully gained a foothold in the wild, the American peregrine is no longer considered endangered. In June 1995 the USFWS proposed removing the American peregrine falcon from the endangered species list, a process known as "delisting." If delisting occurs, the American peregrine will become one of only a handful of species in the United States to have recovered sufficiently to be removed from the list: The others include a dove, a flycatcher, and an owl, all of which live on the islands of Palau. The Arctic subspecies was delisted in 1994. The American alligator is considered recovered, but has not been delisted due to its similarity in appearance to the American crocodile, which is still endangered, and the bald eagle was "downlisted" from endangered to threatened. In addition, some species were delisted because they became extinct, such as the dusky seaside sparrow, or because they should never have been listed in the first place. Currently, there are more than 500 animal and plant species in the U.S. listed as threatened or endangered with extinction.
According to The Peregrine Fund, there are now more than 1,000 nesting pairs of peregrine falcons in the contiguous United States, up from fewer than 50 known pairs in 1975 and 99 known pairs in 1980. The number of known nesting pairs has roughly doubled every five years since 1980, and this trend shows no sign of abating.
According to Koppie, there are about 150 nesting pairs east of the Mississippi, from Maine to Georgia. The USFWS recovery plan calls for 175 pairs. "In 1995, we will probably reach 160 pairs and we should be in good shape to reach 175 by the end of 1996," predicts Koppie.
In some areas the USFWS has surpassed its recovery plan goals. With few exceptions, notably Mexico, where organochlorides are still used, or in parts of California, where organochlorides persist in the environment, peregrines have successfully reclaimed their former ranges. For most of the United States, the release of captive-bred peregrines is no longer necessary. "We've been winding down our release program for several years," states Burnham. "In fact, we've stopped releasing them in all areas except parts of Montana [where to date few falcons have been released]."
Not everyone is pleased with the success of peregrine falcons as urban pioneers. Some say the urban falcons should not be counted toward the USFWS's recovery goals. Craig Koppie disagrees. "You can't tell a peregrine on a skyscraper that he's any worse off because he's eating pigeons instead of wild passerines." Moreover, pigeon fanciers have been known to grumble about the presence of such high-speed killers, and window washers complain of being harassed by the acrobatic birds. Koppie confirms that peregrines are very aggressive. "If you're a window washer, you'll know when you're near a nest."
David Salvesen is a writer and environmental consultant.(ZooGoer 25(1) 1996. Copyright 1996 David Salveson. All rights reserved.)
