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The second habitat component of breeding peregrines is that of adequate hunting habitat. Hunting peregrines will frequently travel at least ten miles to procure prey (the known extreme range of one pair of Utah peregrines was 17 miles). Thus, it is important to maintain the integrity of important hunting areas within at least ten miles of the important nesting cliffs. All habitats within the ten mile radius need not be considered essen- tial since only those areas which serve to attract or support the peregrine's prey need be protected or enhanced. The primary prey captured by nesting Colorado peregrines are small to. moderate sized birds such as blackbirds, doves, robins, flickers, jays, nutcrackers, meadowlarks and pigeons. Any habitat which supports or concentrates birdlife should be considered essential to peregrines nesting in the vicinity. Key hunting areas fall into two categories: 1) those habitats which serve to concentrate or support important prey species. Examples of such areas are riparian habitats along rivers and streams, ponds, marshes, meadows and grain croplands. 2) Those habitats that expose prey and make them vulnerable to attack by peregrines. This category includes pastureland, meadows, grasslands, mountain valleys, gorges (which force prey to cross considerable expanses), lakes and reservoirs. Peregrines capture their prey through precip- itous dives (stoops) from considerable height above their quarry and so they must frequent openings which permit this type of pursuit. They do not hunt below the forest canopy, but take birds that fly above forests or cross open expanses. Generally, the nesting cliffs are situated at considerable heights above the surrounding terrain so the peregrines have a broad panorama from favorite hunting perches near the cliff top. Geographic Description of Habitat Historic Range: Prior to the 1950's, few peregrine falcon eyries were known in Colorado. This was due in part to the lack of knowledge or interest in the falcons and also to the remoteness of the regions they inhabited. The majority of the sites which were known are situated in localities which attracted frequent human visitation (e.g., Estes Park, Mesa Verde and Royal Gorge). At present, 31 sites in Colorado are known to have been occupied. The number of historic sites are bound to increase as further investigations turn up previously unknown breeding peregrines. Due to the tenacity with which peregrines occupy site, it is reasonable to assume that those few new sites which are discovered have a history of traditional occupancy. Prior to the 1960's, a number of sites (at least nine) along the Front Range were occupied. These same sites were among the first to be abandoned. The assumption is that these pairs had greatest access to prey which was laden with persistent pesticides (DDT and others) and experienced reproductive failure first. Gradually, the number of occupied sites have shrunken until only those deep in the intermountain region remain occupied. The following table shows the gradual decline in occupancy and productivity of known peregrine falcon eyries. -41-