As the cheetah is the fastest animal on land, so the peregrine falcon (Falco peregrinus) is the fastest bird in the skies. A member of the raptor family of birds, the peregrine hunts by flying for extended periods at very high altitudes while searching the ground and skies below for suitable prey. When it spots a quarry, it goes into a steep dive, controlled only by the tips of its wings. It is this stoop, clocked at upward of 200 miles an hour, which gives the peregrine falcon its reputation for speed.
The stoop itself is one of nature's most stunning achievements. With the help of modern timekeeping equipment and cameras capable of being fitted onto a small falcon without significantly impacting its performance, the exact dynamics of a peregrine falcon's flight can be seen as never before. We now know that the stoop is not a controlled straight fall but is actually a tight logarithmic spiral. This happens because the peregrine's eyes are set at an angle of about 40 degrees to either side, allowing it to scan a greater surface area for prey, but this also means it cannot best see its prey except at an angle. In order to keep the prey centered within the deep fovea of one of its eyes, the sharpest part of its vision, the stoop becomes a spiral with the prey caught in the middle.
In 2005, Ken Franklin recorded the fastest stoop time yet seen, a stunning 242 miles per hour, just short of the falcon's predicted terminal speed of 250 miles per hour at low altitudes. However, the peregrine is built so well for stooping that its wings are incapable of soaring.
There are unique anatomical problems to moving at such speed. Some are minimized by the behavior patterns of the peregrine falcon, while others are built into the body of the bird. The peregrine falcon minimizes air drag and potential damage to its wings by tucking in its feet and folding back its tail and the greater part of its wings just before it begins its stoop. The pale buff coloring of its underside makes it very difficult for potential prey to spot high against the pale sky, adding to the surprise of the attack, while the slate blue of its upper body blends well into the cliffs and rocky ledges on which it prefers to roost. The damaging rush of air through its lungs is mitigated by small bony tubercles in its nostrils. Its eyes are protected from dust and other debris in the air with a nicitating membrane, sometimes called a third eyelid, while the dark markings around its eyes help reduce glare and improve visual contrast, performing much the same function as eye black for a football player. The prey is struck with a clenched foot rather than caught, which keeps the falcon from becoming entangled with it while at the edges of its own control.
Descending like a bolt from heaven, peregrine falcons were considered sacred birds as far back as ancient Egypt,. where they were associated with Horus, the sky god. In falconry from China to Europe they were esteemed as royal birds, and often it was only the high nobility who were allowed to fly a peregrine falcon. More than simply a hunting bird, the peregrine falcon was also a military asset, since it could bring down carrier pigeons. Thus by World War I, when the sport of falconry had long fallen into decline but carrier pigeons were still used, the peregrine falcon came to be seen as a threat, and thousands were killed. This, along with the widespread use of DDT after World War II, nearly led to its extinction.
Dichlordiphenyl chlorine (DDT) was one of the many miracle chemicals of the late 1940s and 1950s. Proven safe to humans and animals in the concentrations used for spraying, it was a popular insecticide which reduced the incidence of malaria worldwide. Even crop seed was treated with DDT, to protect it from insect predators. However, what no one knew at the time was that its interaction with the food chain would also result in biomagnification, where small concentrations of DDT in the environment became extremely large concentrations inside the animal itself, as smaller animals ate large quantities of DDT-laced insects and seeds and were eaten in turn by predators. In each case, the animal's body accumulated DDT from its diet in its body fat, which in turn began to disrupt its biological systems. Even today, long after DDT has been banned from widescale use, it persists in the body fat of many high-level predators, including human beings.
As an apex predator whose primary diet consists of seed- and insect-eating birds, peregrine falcons were among the most dramatically affected species. The most noticeable effect of DDT in this case was that its byproduct DDE causes falcon eggshells to become so thin that even sitting on them could crack them, killing the unborn young. Even when eggshells did not crack, they were so thin that water could evaporate easily through them, often drying out the egg and killing the chick. Peregrine falcons in the eastern half of the United States vanished entirely. An entire generation of peregrine falcons was nearly lost, and with it nearly the species itself.
When ecologists realized what was happening, drastic action was taken. Eggs were removed from their nests before they could become damaged, and brought to hatching under carefully controlled laboratory conditions. The nestlings were banded and blood samples taken to monitor levels of DDT. (Modern blood samples also include DNA analysis to track breeding populations.) Using a minimum of human contact, the young were carefully socialized to eventual independent survival in the wild. Some captive breeding programs used puppets made up to look like raptor females to feed the chicks and later bait them into flying, in much the same way as their parents would have. Over six thousand such birds have been reintroduced into the wild.
For now, the peregrine falcon is one of the world's greatest conservation stories. In 1999, the peregrine falcon was removed from the endangered species lists, although its numbers continue to be monitored. What has also helped the recovery of the peregrine falcon was its discovery that urban landscapes were not so very different from its native cliffs, and that the multitudes of urban pigeons and starlings could make an acceptable all-you-can-eat substitute for its wild food of doves and song birds. Eighteen breeding pairs of peregrine falcons now nest in New York City, and in London, Ontario, they have been returning to the same skyscraper ledge, conveniently located just across the street from the windows of the public library, for fourteen years. Other popular urban nesting areas include cathedrals and the towers of suspension bridges.
However, the threat posed by biomagnification has not gone away, and the risk to the peregrine falcon is not at an end. Although DDT is now tightly restricted, many other chemicals are continually added to the environment. According to a 2008 study by the California Department of Toxic Substances Control, peregrine falcons in California carry a higher level of polybrominated diphenyl ethers (PBDEs), a chemical used in industrial flame retardants, than any other species in the world. In urban peregrines, many of the levels were so high that their eggs could not hatch.
We know the dangers, now. Have we also acquired the wisdom? It is entirely in our hands whether this beautiful bird will survive to bring joy to the hearts of our children and grandchildren.