The individual home ranges of peregrines can vary significantly and determining the home range can be confusing. Distances between nesting pairs can provide one determinant of home range but is probably misleading if only a linear measurement is used, as the area, in square kilometres, covered by the bird can be quite large. It is suspected that their occupied territory is not a circle radiating out from the eyrie but rather governed by ridges and/or water catchments, with each pair having their own individual "shaped" home range. In some cases, there is probably overlapping areas between pairs. Within each home range there will also be young birds occupying some parts of the area during part of the year. It is also suspected that some individual pairs will be more dominant than others and occupy a larger area. These birds may also tend to hold the larger and best cliffs.
It appears from this study that topography is the key to distances between eyries. Sites divided by watersheds were generally closer, whilst eyries in sight of each other were no closer than six kilometres apart. Distances between eyries where no suitable nesting cliffs are available show large gaps between some sites. It was not apparent that there were pairs in these zones, either non-breeders or pairs using other types of nests such as eagles' nests or hollows. According to Vic Hurley, over a given area of land, there are "spare" birds and these birds may occupy the zones between eyries. Table 3 shows the various distances between breeding pairs.
More research needs to be done to ascertain whether they move to other parts of their home range or migrate locally each year. Radio telemetry could help here. No peregrines were sighted at one major nesting cliff visited at least four times outside of the breeding season.
4.10 Eyries - location