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z Given the saturation of the surveyed cliffs with large stick nests and the proximity of three resident pairs of Golden Eagles, it seems plausible that most of these nests represent alternate sites. Other raptors utilizing stick nests on cliffs include Turkey Vultures, Ravens, Red-tailed Hawks and Prairie Falcons. However, all but location S177 were checked and ascertained to be vacant rn nay. i[ is possible thaE the pair of Red-tailed Hawks frequently sighted over Riley Gulch were using nest 511 One might hypothesize that the Golden Eagles have excluded larger falcons from nesting on the study area. In Great Britain and Scotland Ratcliffe (1962) noted an inverse relationship between Golden Eagle density and that of peregrines and ravens. lie admits this may be cir- cumstantial but feels that competition is keen between them. Dixon (1937) reported the appropriation of a peregrine nest site b}' a pair of Golden Eagles. We could Find nothing documenting competition or exclu- sion of Prairie Falcons by Golden Eagles in the literature. However, Morlan Nelson of Boise, Idaho has done work on this subject (unpublished to our knowledge) and might be an informative contact. It is perhaps significant that a pair of kestrels is nesting a[ the head of Smith Gulch (C ). According to Ratcliffe (1962:28): "Merlins and Kestrels often breed near or on Peregrine and Raven cliffs when these species are absent, and the Kestrel may use their vacant eyries. When the original occupants return to breed, both Merlins and Kestrels dis- appear again, and they are displaced from their usual nesting quarters should Peregrines or Ravens choose to occupy these. Ravens may tolerate Kestrels on another part of the same cliff range but, unless a cliff is extensive, the presence of a Kestrel is usually proof of the Peregrine's absence." A final comment is in order regarding July sightings of Prairie Falcons on the study area. Enderson (1964) describes a habit of these birds to wander considerably after departing from eyrie sites in mid to late June. During this post-nesting season (July-October) pairs may establish residency in open areas with adequate food supply. The proximity of such areas to nest sites is not important. His data suggest that in the Rocky Mountains there is wide-spread seasonal movement of distinct Prairie Falcon populations. Thus, July sightings may not be indicative of nesting birds on the property. Additional information regarding the large Falcons in tl~e more arid, western portion of North America may be found in publications by Ogden (1972), Porter and White (1973), and White and Cade (1971). Addendum: Enderson (pers. comm., 1976) reports the presence of a Peregrine Falcon eyrie in the Roan Creek drainage (one of the six known in Colorado). It is entirely possible that peregrines sighted at the Logan Wash Site are from this eyrie.