This changed during the Peregrine Falcon’s reintroduction as individuals were raised and released into cities. Historically, peregrines were known to nest on old buildings in small towns, but few were observed in urban environments. The species also nests in tree cavities and in the stick nests of other species, on the ground, and on manmade structures. The peregrine’s tenacity to specific sites makes it relatively easy to study its reproductive success, and also has aided in its reintroduction. Nest sites vacated during the DDT era are again being used, indicating that the use of specific sites probably involves more than simple tradition. Peregrines often reuse not only the same cliffs, but also the same individual ledge. It is not uncommon for a site to be occupied for decades and, sometimes, for centuries. Successful breeders rarely change nest sites, and preferred nest locations are passed down from generation to generation. Peregrine Falcons avoid nesting near potential predators such as Golden Eagles and Great-Horned Owls. Peregrines prefer to nest on tall cliffs, and nest success increases with the height and protective nature of the nest site. A nest site must afford protection from the weather and potential predators, and it must be in or near areas with an adequate prey base. Peregrines nest in a variety of cliff types including overlooking rivers and lakes, coastal areas, and mountain valleys. The species prefers to nest on cliffs, and the presence of suitable nest sites often determines its distribution and density. Peregrine Falcons breed in a variety of different habitats across North America. Fortunately, a ban on the widespread use of DDT in 1972, coupled with extensive recovery efforts involving captive propagation and release and the species own reproductive determination, enabled the Peregrine Falcon to rebound to pre DDT-era levels. When Peregrine Falcons consume pesticide-laden prey, the pesticides accumulate in the peregrine’s fatty tissues and eventually interfere with an individual’s ability to produce eggshells of adequate thickness, thereby reducing reproductive success. Peregrine populations were extirpated from most of the species’ original range in the East, and most populations elsewhere experienced declines as well. Populations of this naturally rare species declined across North America during the 20th Century due to widespread use of DDT. There are 19 subspecies of Peregrine Falcons, three of which are found in North America. These “masters of the sky” are fast and maneuverable, not only when chasing prey but also while performing aerial courtship and territorial displays. For centuries Peregrine Falcons have been prized for falconry, especially the larger females. The species is a powerful hunter that is well suited for capturing avian prey. With speed, agility, and a trademark high-velocity stoop, the Peregrine Falcon is often considered to be the perfect flying machine. The species occurs in an extraordinary array of natural habitats, as well as in urban areas. Although widely distributed, the Peregrine Falcon is common in only a few places. Peregrines are found on every continent except Antarctica and some individuals migrate distances up to 25,000 km annually. The word peregrine, which is Latin for “wanderer,” aptly describes this near cosmopolitan and often highly migratory falcon.
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