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..,_._, 1 ' HABITAT FOR THREATENED OR ENDANGERED WILDLIFE IN COLORADO S ep ties: American Peregrine Falcon, Falco peregrinus anatum ' Status: Federal and State Classified as Endangered ' Habitat Requirements and Limiting Factors: Habitat requirements for nesting peregrine falcons in the Central Rocky Mountain Region appear to Efforts are underway to be quite variable from site to site: . delineate common factors which are essential to occupancy of all nesting sites. In general, the sites require two components: 1) adequate nesting habitat, and 2) extensive hunting habitat ' with sufficient prey to support the breeding falcons .and their offs rin p g. Nesting sites (eyries) are located on precipitous cliffs ranging ' in height from 40 to 2100 feet, but cliffs averaging between 200 and 400 feet are most .frequently preferred. Several ledges, potholes or small caves must be present in the cliff face to serve as suitable nest sites. A breeding pair will frequently ' alternate their nesting activities to different ledges ort a cliff face and they will often relocate on adjacent cliff faces, ' (it appears that at least one pair of Colorado peregrines shifted to a cliff one mile distant from the previous nesting cliff). So, protective measures will have to be addressed to an entire cliff complex rather than a single cliff. At higher elevations, cliffs with southerly exposures are preferred. Most peregrine ' nests are located at elevations of less than 9;000 feet above sea level (one site was recently confirmed at 10,500 feet ' elevation). Nesting peregrine falcons will not tolerate exces- sive human encroachment or prolonged disturbance in the vicinity of the nesting cliff. Any activity or development above the nesting cliff will very likely cause abandonment. Breeding peregrines become extremely agitated and may abandon the site if disturbance occurs during the courtship period prior to initiation of egg laying. One explanation as to why some sites were occupied in spite ;of excessive human activity in the vicin- ' ity below the nesting cliff is that the falcons occupied the site early in the season prior to the human activity buildup and had eggs or young when the distrubance occurred. Thus, they were ' attached to the site and would not abandon it at that time. In i Colorado, peregrines generally return to the nesting cliffs in late February or early March and initiate courtship activities which continue through to mid or late April when the eggs are t laid. The young hatch from mid to late May and fledge from the eyrie in mid to late ,tune. The young and adults remain in the vicinity of the nesting cliff up to several months after fledging ' (young were observed in the immediate vicinity of one eyrie through mid September). ' -40-