Formerly on the endangered species list—in fact, it had disappeared completely from the Eastern U.S. by the 1970s because of pesticides like DDT—peregrine falcons are now considered a "species of least concern" and are increasingly common in cities, including New York. 16 pairs are known to live year-round across the city on bridges including the Brooklyn and Gil Hodges, church steeples, and high-rise buildings such as 55 Water Street and the Brooklyn House of Detention.
The natural environment for falcons is high cliffs over large open areas where they hunt. The bird will typically sit very still, watching its prey until it flies into an open area. Then the falcon dives down onto its prey at speeds that can exceed 200 miles per hour—the fastest animal ever recorded! (In order to fly at such high speeds, falcons have a special adaptation to extreme air pressure: a cone-shaped structure inside the bird's nostril, which actually inspired the design of the air intake cones in jet engines.) In the city, they can be most easily seen perched, watching for prey, on a steeple, building ledge, or other high structure.
Like all falcons, peregrines have long, tapered wings and a slim, short tail. They are about the same size as crows, averaging 15-20 inches long and a little over two pounds (1 kilogram) in weight. Female peregrines are larger than males, which is typical of most raptors, but their markings are the same: a slate-gray back and head, light brown-barred breast, and thick black “moustache” stripe. Yellow eye-rings, a white throat, and yellow legs are additional identifying marks. Young birds tend to be darker and browner than adults, and are streaked instead of barred underneath.
Peregrines begin breeding at 2-4 years old, often returning to areas near where they hatched. The nesting season begins in the late winter. In early spring, the adult pair begins its courtship, which includes spectacular rituals where the male circles and dives at high speed. The female lays 4-5 pinkish-brown eggs which hatch in about a month. Both parents incubate the eggs and care for the young. By about 6 weeks the nestlings are ready for their first flight, but they remain dependent on their parents for protection and food for another 8 weeks. Young peregrines are preyed on by larger birds and some mammals, but adults have few enemies and aggressively defend the territory around their nest even from much larger birds of prey. Only about a third of falcons make it through their first year, but those who survive have an average lifespan of 13 years.
Peregrine falcons make a wide variety of sounds for different reasons, mainly during the breeding season. They vocalize to communicate with mates, between parents and offspring, or in other situations and often give a series of sharp, territorial calls while hunting. They also communicate by assuming various postures. Peregrines are able to see small objects from very far away with their extraordinarily keen eyesight. They are usually active during the day and hunt at dusk, but in the well-lit city they may also hunt at night.
Some peregrine falcons migrate long distances, but in temperate climates and along coastal areas like New York City they do not migrate, or move only short distances in winter. About one million peregrines live worldwide in many environments—everywhere but Antarctica, tropical forests, and extreme deserts. In fact, they are the world's most widespread raptor and one of the most widely occurring birds. About 3/4 of their diet consists of small to medium-sized birds, but they also hunt small mammals, including bats. Peregrines in New York City are known to eat at least 75 species of birds, but their most plentiful prey is the rock pigeon—the only land bird that is more widespread.
A lot is known about peregrines; because of their decline and efforts to bring them back they are one of the most widely-studied bird species. To learn more about these fascinating falcons, visit:
NY State Department of Environmental Conservation's peregrine falcon webcams
The excellent Backyard and Beyond urban nature blog also frequently mentions city falcon sightings.