ANIMAL ESTATE client 4.03/8.11: Peregrine Falcon
FROM ANIMAL ESTATES 4.0: SAN FRANCISCO, 8.0: LONDON
SCIENTIFIC NAME: Falco peregrinus
ANIMAL PROFILE: Peregrine Falcons (a.k.a Duck Hawks, no doubt named for their hunting and eating habits) are about the size and weight of a crow - females are larger and more powerful than males. Adults have slate dark blue-gray wings and backs barred with black, pale undersides, white faces with a black stripe on each cheek, and large, dark eyes. Their wings are long and pointed - Peregrines look, in a nutshell, fast.
The Peregrine Falcon mates for life and pairs occupy a home range of approximately 20 to 50 square kilometers. As breeding season nears, unmated males make circling display flights to court females. Mated pairs perform "sky dances" where they swoop and tumble over one another. Breeding season is from August to December and nests are lain in recesses in cliffs, hollows of a tree or in large, abandoned nests of other birds. Ledges of buildings are also used for birds living in built up areas . Between two to six eggs are lain and about 30 days after incubation has started, a muscle contracts in the egg. The chick's head snaps up and the egg tooth, a hard pointed knob on top of the beak, cracks the inside of the eggshell. This creates a "pip" - a small hole with tiny cracks spreading out across the shell. One to two days after pipping, the chick begins moving around in the shell. The egg tooth scrapes against the eggshell, cutting a ring through it. 33 days after the egg is laid, the chick breaks out.
Baby falcons are called eyasses. Eyases are helpless. One parent (often the female but sometimes the male) stays with the chicks while the other finds food for the brood. They are covered by white down when they are born, which is replaced by feathers in three to five weeks. Eyases eat an incredible amount of food - but then, they double their weight in only six days and at three weeks will be ten times birth size. At right around forty days Peregrines begin flying. Although they have a high mortality rate, Peregrines have been known to live as long as 15 years.
RANGE: Peregrines breed locally from Alaska to Greenland and southward to Mexico, Missouri, and northern Georgia. Also throughout the rest of the world. Winters from coastal Alaska and southern Canada southward to South America.
HABITAT: Found in a variety of habitats, most with cliffs for nesting and open areas for foraging. One reason that Peregrine falcon aficionados believe the birds thrive in large cities is the abundance of prey in the form of typical small urban wildlife. Pigeons, starlings, and blue jays make for easy targets and there is not much competition from other predators. Peregrines have been known to prey on rats and ground squirrels for gustatory variety. Also, skyscrapers in the cities that have attracted the falcons have ledges that approximate the cliffs the species uses in wilder settings. However, Peregrines shun building nests, often requiring some sort of box or other modification to prevent the eggs from simply rolling over the edge and the fledglings from falling to the ground. It should also be noted that large structures with plate glass provide a serious hazard to the birds, especially young, inexperienced ones that fly into them.
HOME CONSTRUCTION: Historically, nest sites are used year after year, with some nest sites in North America occupied for more than 50 years, and in Europe up to 350 years. The Peregrine nest is a shallow, unlined scrape. Nest building is not a major domestic activity-instead the female lays the eggs on a cliff ledge, tall man-made structure (usually where nest boxes are provided), or in an abandoned eagle, hawk or raven nest.
THREATS: In non-urban settings great horned owls, golden eagles, and large mammals may prey on young falcons in the nest or at fledging. However, in urban areas Peregrines have relatively few predators. They will battle with any intruding peregrines
In the 1960s, scientists discovered that DDT (dichlorodiphenyltrichloro ethane) was interfering in the egg shell formation of meat and fish eating birds. Healthy birds were laying eggs so thin they were crushed by the weight of the incubating adult. By 1965, no Peregrine falcons were fledged in the eastern or Central United States. By 1968, the Peregrine population was completely eradicated east of the Mississippi River. The use of DDT ended in the United States in 1972. After the banning of DDT, The Peregrine Fund released more than 4000 captive-reared birds in 28 states over a 25 year period.
INTERESTING FACTS: The name "peregrine" means wanderer, and the Peregrine Falcon has one of the longest migrations of any North American bird. Tundra-nesting falcons winter in South America, and may move 25,000 km (15,500 mi) in a year. / The Peregrine Falcon is a very fast flier, perhaps the fastest bird on earth, averaging 40-55 km/h (25-34 mph) in traveling flight, and reaching speeds up to 112 km/h (69 mph) in direct pursuit of prey. During its spectacular hunting stoop from heights of over 1 km (0.62 mi), the Peregrine may reach speeds of 320 km/h (200 mph) as it drops toward its prey. / Falconry is an ancient sport. It was practiced in China before the year 2000 BC: falconry is also the subject of some of the oldest Egyptian wall paintings. Horus, an Egyptian god, was a Peregrine falcon: the "Eye of Horus" is clearly a stylized Peregrine falcon's eye. / At one time, the type of falcon an Englishman was allowed to own marked his rank. A king, the gyrfalcon; an earl, the peregrine; a yeoman, the goshawk; a priest, the sparrowhawk; and a servant the kestrel. Notable falconers and enthusiasts include Frederick the Second (who wrote what some consider the first book of ornithology), William Shakespeare, Marco Polo, and Ghengis Khan.
MAKING A PEREGRINE FALCON NESTING BOX: A standard mount nest box is 22" deep, 22" high in the back, 20" high in the front, and 34" wide. Use T-111 cedar siding for the outside. T-111 siding is lightweight, easy to get, and very durable. A long arm provides a perch for the falcons. It is important to have about 4" to 6" of pea gravel for nesting substrate. Too little gravel could cause egg punctures. Too much gravel will interfere with drainage, causing the box to rot quickly. Drill 15 to 20 small evenly-spaced holes in the bottom for drainage.
Nesting Box Plans:
• The Raptor Resource Project
http://www.raptorresource.org/build.htm
A few Nest Cam Sites:
• USCS: Santa Cruz Predatory Bird Research Group
http://www2.ucsc.edu/scpbrg/falconcamera.htm
• Pennsylvania's Peregrine - Dep Falcon Page
http://www.dep.state.pa.us/dep/falcon/
• Minnesota Power
http://www.mnpower.com/falconcam/
• Ohio Department of Natural Resources
http://www.dnr.state.oh.us/wildlife/dow/falcons/columbus.aspx
• EarthCam - Peregrine nest on the roof of Midwest Generation's power plant in Waukegan, Illinois
http://www.earthcam.com/usa/illinois/midwestgen/
REFERENCE SITES:
San Francisco Field Ornithologists
All About Birds: Peregrine Falcon
The Raptor Resource Project: Falcon Facts
Fourth Crossing Wildlife: Peregrine Falcon
Chipper Woods Bird Observatory: Peregrine Falcon
Golden Gate Raptor Observatory
ESSAY
client 4.3: Peregrine Falcon (Falco Peregrinus)
by Allen Fish , Director, Golden Gate Raptor Observatory, for the Animal Estates 4.0 Field Guide
Once known as the Duck Hawk, the Peregrine Falcon is actually neither. It is thoroughly and purely falconesque -- a block-headed, stiletto-winged, aerial bird-hunter of immense speed and finesse. Early California ornithologists emphasized this falcon's predatory aspect. "To the sea birds in inhabiting the rocky islands off the coast, the Duck Hawk is terror incarnate," wrote Ralph Hoffman in Birds of the Pacific States in 1927. However by 1970, California's Peregrine numbers dwindled from some hundreds of birds to only two known nesting pairs. Suddenly, the "terror incarnate" was itself quite vulnerable, a species hanging in the proverbial balance.
Our recent ancestors were delighted to have DDT around in the 1950s and 60s, and in those days before EPA or endangered species, we applied the insecticide widely to control mosquitoes and other pest-bugs. It was a quiet but sharp-penned marine biologist from Massachusetts who deduced from migrating raptor counts and other sources that DDT was also causing the reproductive failure of numerous bird species. Rachel Carson built this case in her book Silent Spring, which was published in 1962, just two years before she died by breast cancer at age 56. Several years later, biochemists from Britain isolated the chemical events that allowed DDT derivatives to sequester calcium ions in the bodies of female falcons. And Carson had been spot- on: the reduction of calcium meant that the eggs laid by these moms would be too thin-shelled to be brooded without themselves breaking. The result? Widespread Peregrine reproductive failure.
By the early 1970s, scientists, conservationists and falconers rallied to breed Peregrine Falcons in captivity, mainly under the leadership of Tom Cade and the Peregrine Fund, while the newly established EPA took the insecticide off the market in the US. From the mid 1970s to the mid 1990s, biologists with the Santa Cruz Predatory Bird Research Group released some 800 Peregrine chicks to the wilds of the Pacific States, hoping to see the falcons re-establish territories along the Pacific shore and along inland waterways. And they did.
At the end of the century, Peregrine Falcons were back, with several hundred pairs nesting in California, their restoration "nothing short of spectacular," to quote Raptors of California author Hans Peeters. And not only were they nesting in their former haunts -- sea cliffs above the Pacific, and granite ledges above lakes and numerous California rivers -- but Peregrines also became adapted to cities. It turned out that the dull-grey crevices and platforms of skyscrapers and bridges of San Francisco, Oakland, Los Angeles, and San Diego were simply smoother and more geometric forms of their native nesting rocks, providing adequate ledges for perching, roosting, hunting, and even fledging kids. Cliffs and water - life is good.
After years of studying California's birds and having never seen a wild Peregrine, I encountered my very first in 1985, in a quintessentially urban setting: flying over the toll plaza at the Golden Gate Bridge. The falcon was stilling, that is, gliding in place in a stiff wind, about 300 feet up. As I drove slowly toward the toll-taker's window, I realized that the Peregrine was toting prey, some kind of small, obviously-dead shorebird, and as I watched, the Peregrine dropped it. The dead bird fell like a rock toward the road, and as my eyes followed the drop, down, down, down, suddenly the Peregrine was there, hundreds of feet lower than it had just been, and it re-snatched that prey-bird right out of the sky. The same Peregrine! And then it flew back up on high, went hundreds of feet up again, stilled in the stiff Pacific wind, and - as I paid my toll - it dropped the prey-bird a second time. It was playing with its food! Around then, I realized my obligation to safe driving and lost sight of the action. But what a magnificent Peregrine indoctrination that was.
So here are some of the raw details of Peregrine biology. "Peregrine" itself means "wanderer" or "pilgrim" - an apt name as the species is found on all continents excepting the Antarctic, and could be rightly considered the most cosmopolitan of all bird species. Tom Cade has written that Peregrines appear on 40% of the Earth's landmass, in 19 different subspecies. One of these subspecies called tundrius makes one of the most stunning migrations: an annual flight between its nesting grounds in the Alaskan arctic and its vacation home in Tierra del Fuego, the southern limit of the Americas. In contrast, another subspecies, is restricted to the Cape Verde Islands the whole year round.
With three subspecies found in North America, Peregrines show some plumage variation here, but most are large-bodied falcons, one to three pounds apiece, with dark brown or black helmets and a single wide moustache stripe on the side of the face. As with most birds of prey, males are smaller than females, but this is especially true for Peregrines where males are roughly 70% of the weight of the female. In falconry parlance, males are called "tiercels" meaning "one-third of."
Biologists, especially male biologists, have long debated the purpose of this "small-male" problem, which goes by the unapologetically chauvinistic name, Reverse Sexual Dimorphism. One current hypothesis says that for raptors that work hard to pursue dexterous and fast prey (birds!), it is better if the male and the female are widely separated in size so they may better divide the prey species near the nesting territory. And why should the female be bigger? Simple: she does the hard work. She lays the eggs, keeps them warm, and defends the nest.
Speaking of nests, a falcon does not build a stick nest like so many other birds. No, it is cooler than that, taking advantage of existing ledges or caves in cliffs or buildings, where it kicks out a little depression to hold the eggs in place. When not in an urban environment, these "scrapes" are often on large long-standing rocky faces or sea-cliffs (thin of Yosemite's El Capitan) where the Peregrines may have nested for thousands of years, and for thousands of generations. Such sites, known as "aeries' or "eyries" may be critical to the local survival of that Peregrine lineage.
In the scrape, the young downy-white Peregrine chicks are called "eyasses", and over the course of the month after hatching, they eat and grow like crazy, and start to look like real falcons. When they leave the nest, young Peregrines are called "juvenile" and are told by their brown backs and tails, and vertical streaking on their undersides. The streaking runs right up the breast right into the throat area. Young juveniles often show a whitish terminal band on the tail, and the individual tail feather tips look somewhat spikey. Up-close, juvenile Peregrines often have bluish to gray-green fleshy parts (cere, eye rings, and feet) although these may turn to the adult-yellow more quickly than the one-year mark, depending on diet.
Peregrines acquire their adult plumage during the spring and summer of their first "birthday." The adult plumage is grayish in the back and tail -- more blue-gray in males, more brown-gray in females. Adult undersides show fine bars -- short linear marks that cross the body - that extend from the feet to the upper breast. In the "bib" or upper breast, an adult Peregrine either shows clear off-white feathering OR light streaking. Either way, an outstanding field-mark for ageing Peregrines in flight is to watch for the "clear" or nearly-clear throat area. That, combined with a grayish back and tail, signify an adult Peregrine, at least one year of age.