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-. -a- compared with that of the Prairie Falcon in the zones of contact be- tween the two species. Here the utilization by the Prairie Falcon of rodents (especially ground squirrels), reptiles, and birds (to a great extent the same principal shore birds used by peregrines) makes it a generalist in its food habits. In areas of allopatry, as in the deserts, the Prairie Falcon often uses predominantly one or two species of rodents and/or birds and, therefore, in these regions, it is seemingly a specialist. In its nesting site requirements, the Prairie Falcon is a generalist when both allopatric and sympatric with peregrines. In - its selection of nesting sites, it seems to prefer sites which we would consider to be marginal for the peregrine. This more or less limits the peregrine to the more optimal nesting sites and to the role of a specialist. Distribution of free water, and its concomi- tant supply of suitable prey species, is the most important environ- mental factor dictating the distribution and abundance of the Pere- grine Falcon in the arid West. Conversely, lack of free water and its associated supply of suitable prey species is a limiting factor in the distribution and abundance of this species. Climate, on the other hand, appears to be a major factor re- stricting the geographic distribution of the Prairie Falcon as is its strong proclivity to nest on cliffs, thus nearly eliminating the use of tree nests as eyrie sites. In general, however, the selection by the Prairie Falcon of a wide variety of prey species, encompassing three classes of vertebrates, its utilization of several different types of nesting situations, its relatively high reproductive potential, and its ability to exploit successfully the arid environments of western North America points out the ex- tent to which this species has become adapted to its particular environment. With its versatility in selection of prey species and nesting sites, but more especially the former, the Prairie Falcon is among the better adapted and more successful of North American raptors. Because of its extensive utilization of rodents for food, its frequent occurrence in areas many miles from water and many miles from civilization, and its relatively nonmigratory nature, the Prairie Falcon is much less likely to become a permanent victim of the indiscriminate use of the chlorinated hydrocarbons than is the peregrine. The current precarious status of the Peregrine Falcon in Utah is probably a result both of a change in climate and of the inimi- cal effects of man's activities. The future of the species in Utah, as elsewhere appears bleak. Many of the factors responsible for.its decline are still in evidence. The few peregrine eyries still remaining active, as well as the many active Pra`~ie Falcon eyries in the state, should be given the strictest protection and/or management.