Thursday, August 6, 2009

Fastest Bird in the World: Peregrine Falcon

Adult Peregrine Falcon in Flight. Photo by Doug Brown.

Fact or Fiction? Various accounts report top speeds ranging between 100 and 250 miles per hour for the Peregrine Falcon. Most, however, agree that in a stoop (when the bird is diving on prey) that it is indeed the fastest on our planet. Recent technology enabled a team of scientists, lead by falconer and researcher, Ken Franklin, to attach a speed monitor similar to those used in sky diving to his falconry bird, Frightful. National Geographic filmed her remarkable descent as Frightful adjusted her body’s position to become as streamlined as possible once the lure (a leather pouch designed to look like a bird) was released. Although some might argue that since the bird was lifted aloft via aircraft, possibly skewing the results, Frightful reached a top speed of 242 miles per hour while diving on a lure, impressive in the extreme.

Extreme might be one of the adjectives that best describes this remarkable species. Throughout history, humans have been held spellbound by the aerial acrobatics of the peregrine and other large falcons. Few other North American species have been as highly regarded and romanticized in the second half of the 20th century. The peregrine is among the most studied of all wild birds, with over 2,000 scientific publications. The falcon has been eulogized in numerous books and poems, and appears in a wide variety of art dating back several centuries. Its daredevil acrobatics undoubtedly inspired the sport of falconry, where participants may witness these remarkable flights close at hand. During the heyday of falconry in the Middle Ages, the peregrine was the most prized of hunting hawks and reserved for the pleasure of the aristocracy. Severe penalties were incurred for harming a wild falcon or robbing her eyrie (nest).

Revered to reviled: After the introduction of firearms, and conversion of land to agriculture, the sport of falconry declined, and peregrines came to be regarded as vermin, relentlessly persecuted by gamekeepers, hunters, egg-collectors, skin collectors, pigeon fanciers, and others. From the 18th century until the mid 1900s, this attitude persisted and humans destroyed many thousands of peregrines, eggs, and young worldwide. It should be noted that this attitude extended to all raptor species, not just falcons. Yet, falcon populations were remarkably resilient to hunting pressure. One estimate reported a decline of only 10-18% in occupied territories by the 1930s and it was impossible to determine the if they were permanently deserted.

By World War II, the peregrine was viewed as a menace to the all important carrier pigeons, and the British Air Ministry undertook a campaign to eradicate the falcons in the south of England. The control measures resulted in the systematic destruction of 100 or more eyries and shooting about 600 falcons each year. However, within 10 years after the persecution ended, falcon pairs were again present at 80% of those eyries. However, a far greater threat to its survival loomed on the horizon: pesticides.

Vanished: In the mid 1960s, researchers and falconers realized that Peregrine Falcon populations were in deep trouble in North America. A population crash had been occurring for the past 10-15 years, on a parallel with declines of the species in Europe. Except for one eyrie that continued to be occupied until the 1980s, peregrines had vanished east of the Mississippi River. They probably also disappeared from most eyries in the Rocky Mountains at about the same time, although it was not until the 1970s that adequate surveys took place and verified the suspicions of scientists. By 1980, no active eyries could be found in Idaho, Montana, or Wyoming. Suddenly, it seemed as if only 15-20% of the former total population in the lower 48 United States survived.
DDT (dichloro-diphenyl-trichloroethane) was considered to be a safe and effective insecticide in the 1940s and 1950s. It was used as an agricultural insecticide, and to combat lice and mosquitos responsible for the spread of human diseases such as typhus, and malaria. There were no known significant adverse effects to either animal or human health, that is, until Peregrine Falcon populations, along with other birds such as the Bald Eagle and Osprey crashed.
When DDT use was widespread, daily doses of the chemical accumulated in the fatty tissue of the peregrine. The stored chemicals acted to "block" the movement of calcium during eggshell formation causing the shells to be "thin." Peregrine falcon eggs broke and embryos died at an alarming rate. The peregrine became the cause célèbre for the fledgling environmental movement, lead by the publication of Rachel Carson’s landmark book, Silent Spring.

By 1970, the peregrine was federally protected in the United States, and the chemical culprits were banned in North America by 1972. Peregrines were have since made a strong recovery, thanks in large part to extensive captive breeding and release programs implemented by The Peregrine Fund of Boise, Idaho. They were officially de-listed on August 20, 1999, although they remain a state-listed species in New Mexico.

Lessons learned from the plight of the peregrine have worked their way into science curriculums throughout the U.S. Most third and fourth grade students understand what the words “endangered” and “extinct” mean. We are extremely fortunate that falcon watching of this charismatic bird alerted the world to a problem in time for there to be a resolution. Will we be as lucky in the future?

Anatomy of a Rescue

Juvenile Peregrine Falcon (Falco peregrinus). Photo by Doug Brown

The Peregrine Falcon, a highly visible and charismatic species, was proverbial “Canary in a Coal Mine” that alerted us to the dangers of pesticides. Its precipitous decline, discovered in the 1960s, lead to worldwide concern among ornithologists, researchers, and falconers, who convened conferences to assess the situation and implement plans to prevent the falcon from disappearing altogether. Efforts to breed and release falcons began in late 1960s by several different organizations, including the Peregrine Fund, which was founded at Cornell University in 1970 and lead by ornithology professor, Tom Cade.

The P Fund, as it is often referred to now, began breeding falcons in captivity for release to the wild in an attempt to prevent further declines. They successfully bred and released more than 4,000 falcons from 1974 to 1998, resulting in a minimum of 700 re-established breeding territories in North America. The non-profit organization is currently based at the World Center for Birds of Prey in Boise, Idaho.

Peregrines, like other falcons, do not build nests but use naturally occurring cavities (scrapes) on cliff edges, often near water, where the female (referred to as ‘falcon’) lays her eggs on sand or gravel. Generally, these nest sites, called eyries, have an expansive view of the surrounding habitat from which the female can watch for intruders and the male (tiercel) can scan for prey. Peregrines prey almost entirely on birds in New Mexico, including doves, swifts, flickers, jays, meadowlarks, and others. At one eyrie, the remains of 62 bird species were identified. I’ve also watched them hunt for bats emerging from a cave at dusk, and research shows that they are opportunistic, taking other animals on occasion. They can take birds up to the size of ducks and pheasants, hence the nickname, Duck Hawk.

It’s the unique hunting style of the peregrine that has earned the admiration and adoration of countless numbers of falcon fanatics worldwide for, indeed, this falcon has circumpolar distribution, except for Antarctica. The falcon climbs high into the sky, watching for aerial prey below with eyesight that is 8-10 times the distance and acuity of the human eye. Once prey is sighted, the bird tucks its body into the celebrated stoop at speeds of 200 miles per hour or more, and dives on often unsuspecting prey. At the last moment, the falcon swings her balled feet forward and strikes the victim, knocking it unconscious. The falcon then swoops to pick up the prey, and using her tomial tooth (an extra notch on the underside of the upper bill unique to falcons), breaks the prey’s neck. The falcon then descends to the ground with the prey to eat.

Because the peregrine had been extirpated (absent) east of the Mississippi River, but was still present in the West, initial reintroduction efforts focused on this region. Early release sites were located on bridges over rivers that simulated natural falcon habitat and also allowed easy human access, often near major metropolitan areas. The birds took well to these releases and a small population began to thrive. However, although humans thought that the bridges might be an ideal habitat, the peregrines had other ideas about preferred nesting sites. The falcons began to move into cities where they nested on ledges of skyscrapers, and dined on the ubiquitous urban avifauna, notably the Rock Pigeon. It seemed that, in the falcon’s eyes, the city had everything that they needed: suitable eyries and an unlimited food supply.

An additional benefit accrued to the peregrines that took up residence in urban centers, an adoring public. As people became aware of the plight of the peregrine and began to notice the rare falcons nesting outside their high rise, high rent offices, they became falcon watchers and peregrine protectors.

Today, the everyday activities of countless pairs of urban nesting peregrines are chronicled via webcams and falcon watches on the web and in local newspapers. My web search for peregrine falcon news results turned up 119 stories less than 30 days old. This includes last week’s exploits of “Early Bird” a 37-day-old peregrine falcon that leapt from his eyrie on the 12th floor of the Joseph Smith Memorial Building in Salt Lake City. Although the first flight went well, the second did not. He crashed into a flower bed and returned to his nest box by volunteers who keep an eye on the falcons. The volunteers, known as the Peregrine Falcon Watchpost Team, will be on hand from dawn to dusk for roughly the next 10 days in case "Early Bird" or his sibling decides to try again.

Closer to home, peregrines have been observed in downtown Albuquerque although no nesting has been known to occur. Certainly, the falcons are finding ideal hunting conditions in our southwestern city, complete with an abundant pigeon population. One falcon watcher called to excitedly share the intimate details of the recent kill outside her high rise office window.
Not all peregrines have migrated to urban centers, and New Mexico still has a population that eschews city life for the solitude of wilder country. However, getting to see one in the back country is uncommon, even in the appropriate habitat. They remain a state listed threatened species by the New Mexico Department of Game and Fish.
The plight of the peregrine was the impetus for increased research, monitoring and conservation of all bird species. After their success in reintroducing peregrines, the P Fund pioneered propagation and release techniques for numerous species worldwide. Other species released to restore wild populations include the Aplomado Falcon, Bald Eagle, Bat Falcon, California Condor, Harpy Eagle, Madagascar Fish Eagle, Mauritius Kestrel, Orange-breasted Falcon, and Prairie Falcon. However, bringing a species back from the brink of extinction is the least desirable and most expensive way to save a species. The annual costs for recovery of the Peregrine Falcon were placed at more than $5.4 million in the 1990s. Thus, the shared goal of “keeping common species common” is the mantra that drives most conservation efforts today.