Species: Falco mexicanus

Annual mortality estimated at 74% in immatures, 25% in adults (see Evans 1982). Recorded nesting density: 23 pairs on 26 kilometers of cliffs in Colorado, 101 pairs in 72 kilometers along Snake River, Idaho (see Palmer 1988). <br><br>Defend relatively small areas around the nest site. These may extend 300 - 400 meters around the typical cliff nest and about 100 meters above the site (Ogden and Hornocker 1977, Harmata et al. 1978, Kaiser 1986). <br><br>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. <br><br>Where nesting cliffs are suitable and continuous, will nest at higher densities than most other large North American falcons (Steenhof 1998). At higher densities, nest sites tend to be visually isolated from one another (Anderson and Squires 1997). Densities of nesting falcons ranged from 0.2 pair per kilometer of linear cliff in Montana (DuBois 1984) to 0.66 pair per km in southwestern Idaho, with some stretches of canyon in Idaho having 4.3 pair per kilometer (Steenhof 1988). <br><br>Winter home ranges are much smaller than breeding season home ranges but still averaged over 30 square kilometers in Colorado (Beauvais et al. 1992). Winter roosts may be far from winter foraging areas, much as nest sites may be far from breeding season foraging areas. <br><br>Fidelity to breeding territories is very high in some areas. Runde (1987) reports an average 88% return rate in Colorado, Wyoming, and Alberta with Alberta females returning at a very high rate (96%). Return rates in Idaho, where nest sites and mates are at high densities, were substantially lower.