The peregrine nests mostly on precipitous cliffs. In remote relatively undisturbed areas such as the Canadian Arctic, steep slopes, river cutbanks, and even low rocks and mounds may be used. In North America, nests occur only rarely on flat ground or in trees, but such sites are commoner in other parts of the peregrine's range. In southern Finland, for example, there were large ground or bog-nesting populations, which now nest only in northern Finland but at lower densities. In Germany, large tree-nesting populations have apparently vanished.
Peregrines are territorial during the breeding season.
Even in areas where nests are most numerous, nesting pairs are usually more than 1 km, and often much farther, apart. This ensures adequate food for all nesting pairs and their offspring. The immediate nest site is defended against other peregrines, and often against eagles or ravens. An extraordinary feature of peregrines is their traditional use of certain ledges for nesting. Successive pairs have nested on the island of Lundy, off the coast of southwest England, since at least 1243.