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It is an extremely remote possibility that any black-footed ferrets will be found in the survey area. Bald eagles are a • more significant issue. Eagles hunt the prairie dogs towns in and around Dowe Flats in relatively large numbers. '!'he critical questions associated with this issue which must be answered are: (1) how significant is the prairie dog population (at all phases of their cycle) to wintering eagles?; and (2) is the prey base in prairie dog towns surrounding (within 5-20 miles) of Dowe Flats large enough to buffer a reduction in Dowe Flats and accommodate eagles without adverse effect? Obviously, there are other important questions concerning bald eagles and competing raptors whir_h must be answered, but the two listed above are central to the issue. The Johnny darter ranges from Saskatchewan and the Rocky Mountains east to Quebec and south to Louisiana (Baxter and Simon 1970, Woodling 1986). Isolated populations of this native Colorado darter occur in transitional portions of South Platte River tributaries where streams flow from the foothills to the plains (Propst 1982) including the St. Vrain Creek. The St. Vrain should be sampled for the species to assess what potential effects dewatering or increased flows will have on the species locally and downstream. EFFECTS OF RESERVOIR CONSTRUCTION AND USE ON ADJACENT LANDS This broad issue covers a number of related minor issues, some • of which, such as the displacement of deer from the reservoir basin and maintenance of migration corridors, have already been discussed. Some additional minor issues are discussed below. Boulder County is concerned that significant acreage of the Rabbit Mountain Open Space would be inundated by a reservoir at the 5,450 foot pool elevation, and current maps indicate that some inundation of open space might even occur with a reservoir at a pool elevation at 5,400 feet. Resolution of this issue from a wildlife perspective, would, at minimum, require an assessment of wildlife habitats lost vs. those that might be acquired through trade. Equally important to the County is [he need for a buffer zone between the reservoir, and its seasonal recreation uses, and the Rabbit Mountain wildlife sanctuary. For example, Rabbit Mountain is mule deer winter range, a critical habitat. The mere presence of ice fishermen on the reservoir or around its eastern flank would displace deer from the adjacent area making it unavailable during the daytime. The net effect on winter range is about the same as if the same area were underwater. This issue could be at least partially resolved by not developing 14 •