by
Tim Homan
The North Carolina Wildlife Commission has restored a fast and wild ferocity-a taut arrow, feather fletched and set free on the wind-to the state's Southern Appalachian skies. The commission accomplished this feat by bringing back the perfect aerodynamic form of the fastest being on Earth, the Peregrine Falcon (Falco peregrinus). With a moderate amount of luck, you can claim witness to the striking sight of this raptor on the wing, to the fluid grace of its spear-fast flight. With even more luck and more time spent atop mountains open to the high blue, you might witness this falcon turn warlord if another large bird-Common Raven, Turkey Vulture, or Red-tailed Hawk-ventures into peregrine airspace while the proprietor is on high-altitude patrol. Then this predator may tuck its dagger-tipped wings into one of the Earth's most exquisite expressions of form and function as it dives toward the intruder.
This falcon's form is sleek and lethal; it is the shape of an avian weapon, a warrior shape. The peregrine's long, wind-honed wings sweep back beyond its elbows into a narrowing blade. The arc from one wingtip to the other, along the leading edge of the wings, delineates the pronounced bend of a bow. When I see a peregrine falcon from above, this bird of prey reminds me of a flying crossbow, arrow always nocked and ready to rip into the wind.
Mature peregrines are colored dark bluish gray on their upper parts and mostly white or pale rufous with a variable amount of blue-gray spotting and fine barring on their undersides. This raptor's hook-billed head is capped with a bold pattern of black that extends from the base of the bill across the back of its noggin and below its eyes. This diagnostic field mark dips well below the eyes in the approximate configuration of a cold-weather cap's ear flaps. Immature birds are brown where the adults are blue-gray or black. From a distance, the best way to identify this species is by its size, its distinctive falcon wings, and its graceful easy speed. (During the breeding season, the peregrine is the largest falcon in eastern North America south of the tundra.(1))
Peregrine sexes are outwardly very similar in appearance except for their pronounced sexual dimorphism in size: the females are significantly larger than males in all major dimensions. Females usually weigh from 30 to 36 percent more than the males. The total length of the female is 17.7 to 22.8 inches, the male 14.2 to 19.3 inches. The female whips the wind with wings spanning from 43 to 46 inches. In the language of falconry, it is the female that is known as the falcon; the male is called a tiercel because he is approximately one-third smaller.
The peregrine comes to glory in speed. Evolution has tested the limits of avian morphology in the sculpting of the peregrine's high-performance body, a genetic masterwork designed for speed. This bolt out of the blue is the fastest feathered arrow in Mother Nature's quiver. This raptor's flap-and-glide, heading-out-to-hunt pace is a poky twenty-five to thirty-four miles per hour. Rapid wingbeat flight ratchets up to a higher gear, forty to sixty mph. When this falcon flies with a hungry will in pursuit of fast prey, it regularly reaches speeds of seventy as it pumps its wings deeper and faster to close in on its quarry.
Seventy is fast. But seventy is only a warm-up wind sprint compared to this raptor's legendary diving speed. When this falcon folds its wings and drops down at a steep angle, a stoop often plummeting thousands of feet in a few moments, gravity and natural selection team up to test the tensile strength of feathers and air-filled bones as the bird buries the needle beyond astounding into disbelief.
The heavier the bird, the faster the stoop, so it is obviously the females, falconry's falcons, who reach the highest dive speeds. Speeds at or near terminal velocity require a drop of at least 3,280 feet (1,000 meters). Most top-end speed readings-from airplane pilots, free-falling parachutists, air and ground radars-range from 200 to 220 mph. Theoretically, the heaviest of the female peregrines (the largest female of the largest subspecies weighed 3.5 pounds) diving at a near vertical angle could gain the terminal speed of up to 240 mph after a freefall of at least 3,280 feet. Most of the peregrine's predatory stoops, however, are executed at angles from 30 to 60 degrees.
In 1984 the North Carolina Wildlife Commission began a hacking program to reintroduce captive-raised peregrines into the wild with the goal of re-establishing a breeding population in the state. The commission continued this program until a total of ninety-two falcons had been released into the wild by 1997. In the Shining Rock region of the Pisgah National Forest, biologists utilized a pair of craggy, 6,000-foot peaks-Sam Knob and Tennent Mountain-as hacking sites.
The Peregrine Falcon needed all the assistance it could inspire because its population had plunged with almost the same graph-trajectory as one of its astounding dives. The breeding-pair numbers of this species had bottomed out to zero over huge swaths of its North American range.
From the late 1940s to the early 1970s, massive continent-wide spraying of organochlorine pesticides, primarily DDT, resulted in the accumulation of toxic residues (DDE, the persistent environmental residue of DDT) in prey species, which in turn contaminated the Peregrine Falcon. In North America, the peregrine's population dropped throughout the 1950s into the mid-1970s. This precipitous decline was caused by reproductive failure; peregrine eggshells were so thin they broke or collapsed beneath the weight of the brooding parent. In 1968 biologists linked the eggshell thinning to the ingestion of their prey species, primarily avian, poisoned with pesticides.
By 1970 this charismatic species had been totally eliminated as a breeding bird in the United States and southern Canada east of the Rocky Mountains to the Atlantic coast south of the boreal forest. Peregrine populations were also greatly reduced in other sections of western United States and Canada.
Canada restricted its use of DDT in 1970. During that year the U.S. Fish and Wildlife Service first listed F. peregrinus as an endangered species under the Endangered Species Conservation Act of 1969. Two years later, on the last day of 1972, the Environmental Protection Agency belatedly banned the use of DDT in the United States. The Endangered Species Act, which replaced the ESCA, was signed into law on December 28, 1973.
The Peregrine Falcon greatly benefited from its iconic status as a much admired sleek and sexy speed demon. Few other North American species held such a high scientific and public profile in the last half of the twentieth century. This symbol of martial prowess became a leading cause célèbre of the environmental movement of the 1970s.
After DDT was banned in the U.S., one of the Earth's most remarkable evolutionary efforts suddenly had a shot at survival. An alliance of federal and state agencies, conservationists, and private groups rallied behind this compelling raptor, contributing money for captive-breeding programs and donating time to protect pre-fledgling young as they were brought back to their native habitats. Experimental releases of captive-bred birds by hacking and fostering began in the U.S. in 1974 and 1975. By the early 80s peregrines were again flying high, fast, and wild in some of their former ranges.
Although the peregrine is well known as a highly adapted hunter of flying bird brethren, it is not a tiny-niche dietary specialist. This speedster is a generalist that catches and kills an incredibly diverse number of birds as well as a lesser array of non-avian species. Birds comprise 77 to 97 percent of its prey (numbers not biomass), usually passerines (songbirds) to small geese, and including smaller birds of prey such as American Kestrel, Merlin, and Sharp-shinned Hawk. The size of its feathered prey varies widely from Sandhill Crane to the smallest of songbirds.
In addition to a menu of over 500 bird species, the peregrine also snatches other winged prey: at least ten species of bats. Falco peregrinus also throws a few non-winged mammals into the stewpot, primarily a small number of rodent species-mice and rats, ground squirrels and lemmings. In a pinch, this raptor also captures a few amphibians, insects such as grasshoppers, crickets, dragonflies, and butterflies, even a few kinds of fish.
Formerly known as the duck hawk, this species is a versatile hunter, fast and fierce, agile and powerful. The peregrine is acrobatic enough to employ an aerial stunt as hunting technique. It flies beneath its prey, spins halfway around to upside down, then deftly snatches the bird before finishing the barrel roll, the maneuver accomplished with astonishing speed and superb talon-eye coordination. The peregrine is also powerful enough to kill or knock out cold a Sandhill Crane with a punch to the head delivered at high speed. And it is plenty fast and agile enough to frequently capture extremely aerial birds such as the White-throated Swift and Black Swift. When you stand at the edge of the North Rim of the Grand Canyon and marvel at the speed of the White-throated Swifts that have just rocketed right over your head, you have a hard time believing they are vulnerable to airborne predation.
This raptor usually snatches small birds out of the air with its sharply hooked talons, four per foot. But when the intended target is significantly larger-a good-sized duck for instance-the peregrine frequently employs its best known and most dramatic hunting technique: the stoop, a spectacularly swift and steep power dive from the air above. At the deadly end of its stoop, the peregrine punches its feathered prey in the head, the wing, or the back-killing, stunning, or crippling. The strike is a blow from the falcon's rather large feet. High-speed cinematography has revealed that all of the taloned toes are widely splayed at the moment of impact, then the toes instantly clench into a driving fist.
Although widespread (peregrine means wanderer), this winged predator never patrolled the skies in large numbers; it was never abundant or even common over most of its breeding range. This raptor requires a large hunting territory centered around a suitable nesting site, usually a ledge on a high cliff. In North America, the peregrine's largest contiguous breeding areas occur in the west and in the far north. Breeding ranges in eastern North America are often small, disjunct, and hundreds of miles from another wild-land nesting area.
North Carolina's re-established peregrine population is a continuing success. During the last twelve years, from 2008 through 2019, an average of eleven territorial pairs per year have been documented in North Carolina. The lowest two-year total during that time span occurred in 2011 (8) and 2012 (9); the highest two-year total since 1997 occurred in 2017 (14) and 2018 (15). Thus far all but one of their nesting sites have been located on high cliffs or domes in the mountains of western North Carolina. The lone exception was the pigeon-eating pair that set up rent-free housekeeping on a manmade ledge way up in a highrise in downtown Charlotte. This species mates for life and typically returns to the same nesting ledge, known as an aerie, every year. The maximum longevity records from banded wild birds ranges from sixteen to twenty years.
Nearly 7,000 peregrines had been released in Canada and the United States by 1998. The recovery goal under the Endangered Species Act was set at 631 breeding peregrine pairs in the two countries. By 1999, when the U.S. Fish and Wildlife Service removed the peregrine from the death watch of the Federal Endangered Species list, 1,650 pairs had established breeding territories in the two countries.
At the 2014 Wildlife Society Conference, U.S. Fish and Wildlife Service (USFWS) biologists estimated that a minimum of 3,568 nesting pairs of peregrine falcons swooped through the skies of the United States alone in 2012. The biologists went on to say that the species is doing well in all but the U.S. Southwest. Peregrine numbers are growing in the U.S. Northwest, and the population remains small in the U.S. Southeast (as it was historically), but continues to grow.
The USFWS was scheduled to conduct its final post-delisting, nesting-season survey of the Peregrine Falcon in 2015. Due to declining budgets in the USFWS Endangered Species Program, the agency did not have sufficient funds to fully fund this monitoring work across the continental U.S. in that year. The USFWS surveyed only the Southwest in 2015. The 2015 data suggests the U.S. peregrine population continues to grow, particularly in the Northwest; 3,568 nesting pairs is likely conservative because full censuses are no longer conducted in many states. Continental U.S. estimates of territory occupancy, nest success, and productivity also suggest that populations are doing well except in the U.S. Southwest.
This raptor remains protected, status endangered, under North Carolina's State Endangered Species Act, and nest-site monitoring efforts continue with the help of volunteers.
From 2004 to 2011, I dayhiked and backpacked in the Shining Rock region of North Carolina's Pisgah National Forest. From April's wildflowers to October's fall foliage, I walked on weekends, holidays, and frequent days off work for pleasure and to gather hiking-guide data from measuring wheel, GPS, and notebooks full of Southern Appalachian diversity (2). One of the greatest pleasures of hiking in the area year after year was spotting the fleet-winged flight of Peregrine Falcons.
I witnessed their flight in front of the Devils Courthouse cliff face several times. I saw their characteristic coursing flight from the top of Tennent Mountain, Black Balsam Knob, and at least four times from the rocky topknot of Sam Knob. In late June of 2011, as I sat atop Sam Knob (just north of the Blue Ridge Parkway, just east of NC 215, and just south of the Shining Rock Wilderness) trying to record accurate elevation readings with my new GPS, I noticed a pair of Peregrine Falcons-their weight balanced on the slight breeze as if tethered-above and out from my rock-outcrop perch. Both of their slender bodies were aligned in the same direction, and both appeared to be staring at the same spot far down into the valley. I followed their gaze down Sam's southeastern slope and saw what I suspected their eyes were tracking: a Turkey Vulture, its dihedral wings tilting side to side as it lazily followed Flat Laurel Creek downstream.
The larger of the two falcons dipped out of the two-bird formation, flew diagonally to the right away from me and the moutaintop for perhaps 80 yards before banking, wheeling halfway around, and folding her long narrow wings tight to her streamlined body. She released her hold on the sky and dove. She swooped down the long green wall of the slanting mountainside. Even though her stoop was far short of the drop-distance needed for terminal velocity, she zoomed down the slope toward the unsuspecting intruder faster than seemed physically possible. Her swiftness blew away all of the other baselines for avian speed I had witnessed. She shattered them all. Surely she had slipped into a seam in the sky where the physics of friction did not exist.
The feathered projectile buzzed past the vulture about 5 feet in front of its naked red head, scaring the wits and whitewash out of the undertaker. The vulture faltered, flew as spastic as a fledgling for a few moments. The peregrine pulled up out of its dive like a fighter jet, then banked toward a close-quarter dogfight. Only no talons turned to socking fists. After showing off its big-stick speed, the feathered fighter circled around to escort the eager-to-leave bogey out of the no-fly zone.
Two out of the last three times I walked Green Mountain Trail's (3) high-elevation southern half in the Middle Prong Wilderness (separated from the Shining Rock Wilderness by two-lane NC 215), I had the good fortune to witness a falcon flying directly above the high ridgeline down and to the south toward the gap just north of Mount Hardy. The last time, in June of 2015, I watched in amazement as a big peregrine engaged three ravens in what appeared to be a mock dogfight. The female falcon harried and herded the three ravens as she swept them down the ridgetop with ease. Even though the fierce raptor never ruffled a raven's feather, her exhibition-a practiced dance of acrobatic agility, closing speed, and single-minded aggression-was an overpowering display of aerial superiority.
Notes
The next time you marvel at the fast arrowing flight of a duck, praise a raptor: the Peregrine Falcon. Early ducklike species passed through natural selection's long and relentless wringer. Waterfowl evolved, in part, from the work of other wills, ones turning the death of ducks into their own continuance. The pruning talons of the peregrine-with help from the larger accipiters, other large falcons, and falconlike forbears long extinct-plucked the slowest ducks out of the gene pool over geologic epochs, a slow and steady field test of survival and death for both duck and falcon.
The peregrine became one of natural selection's many instruments, a feathered paring knife, that sculpted ducks into today's streamlined birds with musculatures evolved to deliver a furious, revved-up flap rate. The faster ducks did some passive paring of their own. They selected for faster peregrines, who, in turn, selected for faster ducks: evolution's constant thrust and parry, measure and countermeasure, predator and prey honing each other on the same razor strop.
The gifts of inherited grace and guidance insist that shorebirds fly in fast, dense flocks. They instinctively know a Peregrine Falcon won't enter their birdshot maelstrom of beating wings and hurtling bodies. They also know trailing birds invite attack.
The next time you see a flock of shorebirds bend and wheel with the split-second firing of a single synapse, rapidly changing shapes and colors, thank the peregrine again for this wonder of astonishing synchrony. This wonder looks like the work of a single will, a kind of collective or mutual mind-a single flipped switch turning on a thousand lights at once-but the truth is simpler and only slightly less amazing. Each member of the flock turns with split-second speed.
Over the long span of time since the late Tertiary period, peregrines and their falconlike forbears have culled the stragglers-the slow, the indecisive, the uncoordinated-from the edges of speeding flocks: natural selection's slow and steady addition by subtraction. The peregrine and natural selection-a seeing marionette played by a blind puppeteer-shaped the modern marvel of shorebird flock flight. They are an exquisitely precise drill team, one of evolution's finest achievements. And they should be. Their seemingly perfect turning, timing, and spacing at top speeds are the genetic legacies molded by millions of years of try-outs cut from the team. Those cuts not only sharpened shorebird flock flight but also insured that the never-friendly skies would sharpen them further still.
Thanks go to Christine Kelly, Mountain Wildlife Diversity Biologist, for the information concerning North Carolina's peregrine recovery program.
Additional information came from various bird guides, magazine articles, and especially the comprehensive The Birds of North America (A. F. Poole and F. B. Gill, editors) Cornell Lab of Ornithology, Ithica, NY.
Information about the final, 2015 nesting-season survey came from USFWS websites followed up with a few phone calls to USFWS employees.
(1) The larger Gyrfalcon winters irregularly south into the northern states across the contiguous U.S. from coast to coast.
(2) Hiking the Shining Rock & Middle Prong Wildernesses
(3) The 5.6-mile Green Mountain Trail runs north-south through western North Carolina's Middle Prong Wilderness (approximately 7,460 acres, Pisgah National Forest, (approximately 450,232 acres), Haywood County). Walked north to south, low to high, this route's first mile is the steepest trail segment I have ever pushed a measuring wheel up.
