Among the cities which have had nesting Peregrines in recent years are Toronto, Hamilton, Ottawa, Detroit, Columbus OH, Buffalo, New York, Boston, and Pittsburgh. To a Peregrine, a sheltered ledge high on an office tower is much like a towering cliff. Some Peregrines scrape out a small nest in loose gravel or debris on their chosen ledge, but in many places human observers are now providing gravel-filled nesting boxes for them. The boxes provide added security for the Peregrines by preventing the eggs from rolling off the ledge. In some situations the box also shields them somewhat from the elements, and from the eyes of predators.
Peregrines usually are quick to accept the nest box when it is offered.