Restoration Potential: Will use artificial nest sites excavated or blasted into cliff faces. Construction of artificial nest sites has been effective where natural sites are limited but other features of the cliff and the surrounding landscape, particularly the prey base, are suitable (Fyfe and Armbruster 1977, Boyce et al. 1980, Mayer and Licht 1995). As nesting densities frequently are limited by site availability (Squires 1986), this provides a management tool to attract falcons into areas with insufficient nest sites. Prairie Falcons also use "high walls" that can be left behind following coal strip mining (Anderson and Squires 1997). This practice creates artificial cliffs where none existed before. Artificial nest sites should be on south-facing exposures and 2/3 of the way up the cliff face. The floor area of the site should be 7000 sq cm, with a 5-10% slope toward the front. Other characteristics are given by Runde and Anderson (1986), Runde (1987) and Anderson and Squires (1997).
Falcons can be bred in captivity but the reintroduction of captive Prairie Falcons has been very limited (Granger 1977, Anderson and Squires 1997). All evidence is that such extreme measures are not needed or useful at this time, given the many other characteristics of the species that make it amenable to a variety of habitat management actions.
Preserve Selection and Design Considerations: NEST SITES: Will use a variety of landscapes and vegetation types if suitable nest sites are available. The most common type of nest site is a cliff, ledge, rock cavity, isolated rock outcrop or similar site. However, some birds will use trees, power poles or even buildings (Steenhof 1998).
NEST SITE AREA REQUIREMENTS: The size of the nest site territory is not as important from a spatial management standpoint as is the size of the areas required for foraging. Some stretches of canyon in Idaho have nesting densities as high as 4.3 pairs per kilometer (Steenhof 1998). This density might serve as an upper limit for management objectives in areas that are suitable for nesting falcons.
FORAGING AREA REQUIREMENTS: Foraging areas are large, overlapping and not defended (Haak 1982, Squires 1986, Hunt 1993). Steenhof (1998) reports nesting season home ranges from six studies that ranged from 59-314 square kilometers.
Populations are strongly dependent on populations of ground squirrels during the breeding season, especially SPERMOPHILUS species. Thus, maintaining healthy source populations of Prairie Falcons is directly dependent on managing habitat for ground squirrels. The ground squirrels almost uniformly thrive in early successional vegetation. Popular secondary prey species, Horned Lark (EREMOPHILA ALPESTRIS) and Western Meadowlark (STURNELLA NEGLECTA), also are common in low stature, early successional types. Falcons take most prey on or near the ground by "strafing" wherein birds fly fast at only 3-6 m above the ground and surprise prey items (Phipps 1979, Squires et al. 1989, Steenhof 1998). Thus, falcons must have clear vision of the ground level, unobstructed by tall and/or dense vegetation (Brown and Amadon 1968, Haak 1982, Peterson 1988, Squires 1986, Squires et al. 1993). Many North American habitat types generally meet this description: shrub-steppe desert, grasslands, tundra, and arid plains. Periods of higher than average precipitation may affect foraging efficiency in some vegetation types when vegetation grows taller and more dense (Steenhof 1998).
Core use areas in Alberta had lower proportions of irrigated cropland than expected by chance (Hunt 1993) and prey biomass is lower in agricultural lands. This suggests that fragmentation caused by this factor at least, may have adverse effects. Simulations for southwestern Idaho (Steenhof 1998) predicted that loss of as little as 15% of the land to agricultural conversion could reduce falcon productivity below replacement levels. Although large-scale agricultural development is implicated in population declines in several areas (reviewed in Steenhof 1998), small-scale agriculture may benefit falcon populations when it provides edge for prey populations (Harmata 1991, Hunt 1993, Marzluff et al. 1997).
During winter, and in some geographic areas during the breeding season, individuals hunted most often from perches (Enderson 1964, Phipps 1979) or by soaring (Kaiser 1986). This suggests that in some cases, birds could persist in smaller habitat patches, other factors being equal.
High levels of site fidelity suggest that in many nesting areas, it is important to protect the nesting territory and adjacent foraging sites with permanent, long-term strategies and not force birds to move among years or expect them to disperse and breed successfully elsewhere when habitat conditions deteriorate. Although data on fidelity to winter sites is much more limited, those data also suggest a strong site fidelity. Thus, identification and proper management of winter sites also may be important.
Management Requirements: NEST SITES: Because nest sites are relatively specialized and because site fidelity is high, the protection of nest sites obviously is a high priority. In geographic areas where inventories for nesting falcons have not been conducted, topographic maps will provide excellent information on cliffs that might support breeding birds. All known and potential nesting cliffs should be considered for conservation action.
GROUND SQUIRREL PREY POPULATIONS: Ground squirrel prey populations are as essential to falcons as are good nest sites. Ground squirrel populations can be lost or greatly reduced when habitat is altered by conversion to agricultural lands, improper livestock grazing, invasion of exotic vegetation or by other activities. As reviewed above, certain small-scale agricultural conversions may be beneficial to ground squirrels but large-scale conversions are almost certainly detrimental. Poisoning of ground squirrel populations has been underway for many years in many geographic areas and this activity likely has contributed to severely reduced populations of several ground squirrel species (Wisdom et al. 2000). Management to protect, enhance and restore ground squirrel populations in key areas should be considered.
FORAGING AREA REQUIREMENTS: The large breeding season and winter foraging areas (30 - 314 sq km) give us a clear perspective on the geographic scale of areas where falcons are to be conserved. Although falcons do not use all the areas within these large home ranges, land managers truly must think in terms of managing landscapes, not sites.
HUMAN DISTURBANCE: Limiting the types and levels of human activities near nests has been a common management strategy, particularly among federal land management agencies. Suter and Joness (1981) recommended buffer zones of 1 km around nests while Becker and Ball (1981) recommended 400 m. Holthuijzen et al. (1990) found that blasting need not be restricted at distances greater than 125 meters from occupied nests. Land management agencies use quasi-standardized distances for oil and gas development, coal development and other activities. Birds can tolerate some development in foraging habitat if nest sites are not overly disturbed (Anderson and Squires 1997). Where nesting falcons occur in high densities, permanent protection of the nesting cliffs, with sufficient buffers, should be sought.
GRAZING: The effects of livestock grazing are not simple and likely vary by region, soil type, vegetation type and many other factors. Thus, it is necessary to study the relationships among the grazing programs, the vegetation and the prey populations to determine the best course of action on any particular site.
INVASIVE EXOTICS: Fire management, livestock management and other actions to slow or stop the spread of invasive exotic plants is critical to the future quality of Prairie Falcon foraging habitat in southern Idaho and other areas susceptible to dominance by weedy species (Marzluff et al. 1997, Wisdom et al. 2000). Direct habitat restoration likely will be required in some areas to augment and rebuild falcon foraging habitat.
ENERGY DEVELOPMENT: Where coal, oil and gas development has occurred, it may be direct human disturbance (see above) more than the physical alteration of the land that impacts falcons. Thus, buffer zones and seasonal restrictions of the timing of human activity and site occupancy may be the most critical factors to manage.
In the United States, management of oil and gas, coal, oil shale, phosphate and other leasable minerals is regulated under the Mineral Leasing Act of 1920 (43 CFR 3000). The best opportunity to protect habitat comes during federal land use planning (USDA Forest Service 2000, USDI Bureau of Land Management 2000a, b). Objectives, standards and guidelines can be incorporated into the Management Situation Analysis and for coal, the Unsuitability Criteria. Where necessary for maximum protection, plans can allocate areas to No Surface Disturbance or Unsuitability. Another opportunity to protect habitat from the adverse effects of these developments occurs during the leasing process. A Notice of Intent is required for exploratory activity that can be very disruptive in the short-term on local sites. Stipulations that protect an area from disturbance during a particular period of the year or that require buffer zones also can be specified. These and other restrictions can be placed as Conditions of Approval when an Application for Permit to Drill is filed, in the case of oil and gas development. Once enough successful wells (5-6) are in place, then a Plan of Development is required for the field. Detailed NEPA analysis is required at this stage and a variety of mitigation measures can be negotiated.
RELATIONSHIPS WITH OTHER SPECIES: Because falcons are tolerant of Common Ravens and use old raven nests, raven management should be carefully considered where they do, or could, co-occur with falcons. Conversely, Golden Eagles, Red-tailed Hawks, Great Horned Owls, and Peregrine Falcons all are detrimental to Prairie Falcon populations. Tradeoffs in management of these various species must be carefully weighed.
PREDATORS: The chief mammalian predators of Prairie Falcon nests and nestlings (coyotes and bobcats) are common and widespread. As with most predator issues, the best approach to minimize predation is to provide high-quality habitat for the focal species. In this case, the provision and protection of good nest sites is the best strategy.
DISEASE: The impact of Rock Doves infected with trichomoniasis and herpesvirus on falcon populations is not known. However, Rock Dove control should be an obvious option where these doves are nesting in the wild on cliffs frequented by falcons or where they are otherwise available to falcons as prey.
SHOOTING: Shooting can be prevented through a constant program to educate the public on the value of falcons and the illegality of shooting them. Road access to areas where falcons need further protection from shooting can be eliminated or reduced.
ELECTROCUTION: Electrocution losses can be eliminated or greatly reduced by continuing to pursue programs that make power lines and facilities raptor safe (Avian Power Line Interaction Committee 1996).
FALCONRY: Although Steenhof (1998) states that the low level of harvest probably does not affect overall population size, disturbance at the nest site (Conway et al. 1995) does have impacts and should be further investigated. Further, in the absence of population data sufficient to model impacts, the continued harvest of wild birds for falconry must be questioned.
COLLISIONS: Elimination of fences in important foraging habitats could reduce this source of mortality. Unfortunately, this is apt to be impractical in many areas. Placing marker balls on wires to minimize collision mortality (Anderson and Squires 1997) might also be effective for problem sites. Where vehicle collisions are a problem, road closures, rerouting or signing (i.e., "Falcon Crossing") should be considered.
STOCK TANKS: Federal land management agencies have policies to provide escape ramps in livestock watering tanks. These policies and their enforcement should be examined for all land within the range of the Prairie Falcon. Similar policies should be implemented on grazing lands controlled by state agencies. Education and encouragement for private landowners also should be pursued.
ECTOPARASITES: Several ectoparasites contribute to nestling mortality and subsequent reproductive failure (review in Steenhof 1998). Hand treatment of nestlings to kill parasites is one option to improve nest success.
PESTICIDES: The use of pesticides known to be harmful to falcons should be discouraged or eliminated in foraging areas where falcons nest and winter. Although this may be impractical on a broad basis, it should be pursued where falcons concentrate and where agricultural lands are interspersed with frequently used native vegetation.