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Peregrines, page 3 ~J L) tho same year usually i.nvulves a shifC in nest n.i te. Cliffs Icnd to rep ro.~ent the eyuivalenC of escape cover. Successful eyries may have Co be nt leas[ onc- half mile from [he ncarc~t hwnan habitation, unless the cliff is parCicularly high and precipitous: (Ilickoy and Anderson, 1969). Several iuvestigaCUrs have observed tlvtt what seems to be suitable nes Ci.ng habitat i.s noC presently occu- pied, and in :ome cases ai~penrs never to have been used. Avni.l ab lr data :jllgl; L`SC [ha[ only certain cliffs rniC of all. ChO:ii: HV a11aI)1C :IrC aCCCp t:161C', alld Lha C. these cliffs arc used year afCCr year (Whiff and Cadu, 1971). Uetcrioracion of Che habitat is not the major problem for the peregrine falcon. liven stags with dense human populations like California and Colorado have more than enough suitabl.c nesting sites Cor Chu present populations. 'fhc major problem stems co be that. relatively few pairs arc breeding. Increasing development of Che West, resulting i.n loss of habitat, is having nn effect on western populations. YroCectinn of existing nest .iCCS and hrccd~ing pairs is thus very impor[anC. ~(Snuw, 1972). Peregrines, fur the most part, Lave been tolerant of human intrusion into nesting territories. 'They have even nesCed successfully on skyscrapecs in large cities. Researchers disagree on Che impact of visits to the eyrie. Some feel Chat eyries should not be visited at all, while others think that there are no harmful efCcr[s caused~by human ncCi.viti.es (Snow, 1972). Nelson (1970) believes Chat there is a shorC period prior to and during egg laying when desertion of a nest ledge can be caused even by careful visits by man. Cade, f:ndet'sun, White, and Craig have also questioned Che possible effects of. eyrie visitations on peregrine behavior (Scow, 1972). The critical period when desertion may occur is probably as variable as Che behav.iur of individual birds. Five pairs may tolerate activiti:s by man that Che sixth pair WL11 not; yeC the sir.Cli is the only pair which breeds succes:ful.Ly; therefore disturbance oC the si>:eh pair is very serious to population survival (Snow, 1972). (in Alaska] oil exp]oraCion teams have unintenCionally caused [he deaths of peregrine nesClings by Irig;htening them from their nests tahile Lalcing gcolof;ical samples from Ulc nesting; cliff. Ncs U fags incapable of flight were killed by the fall. In some instances adulCS deserted Clteir eyries. (Craig, 1972). A definite possibility for habitat management is the restriction of acti- vities around known e}'cics during the breeding season, ns there arc cerCa~in times of Che year when tLc'sr_ sites arr_ vulnerable [o hwnan disturbance and other tl.mes when they arc nut (Snow, 1972). References: Cadc, T. J. 19G0. L:colug;y of f.hc peregrine and gyrfalcon populations in Alaska. Univ. Cal. Publ. 'tool., 63:151-2G7. CraiL, G. ]972. Pcrson,)1 canmunicaCion to C. Snow. tindorson, J. II. 1969. Population trends nmoug peregrine falcons in the Rocky AtuunCain region. in Peregrine Falcon Popu].aCions. J. .1. llickcy (ed.), Univ. Wiscunsi.n Yress, hlilwaulutu. _ f:ndcrson, .1. 11. 1972. I'orsun,tl conummication Lo C. Snow.