Ferruginous Hawk Populations and Habitat Use in North Dakota

Populations of ferruginous and Swainson's hawks increase in synchrony with ground squirrels

“…2). These increases were unexpected because in comparison with other areas, the Hanna study area, even before 1986, harbored one of the densest nesting populations of ferruginous hawks (0.3 -6.3 pairs/ 100 km2, Olendorff 1973; Lokemoen and Duebbert 1976;Smith et al 1981;Blair and Schitoskey 1982;Gilmer and Stewart 1983) and Swainson's hawks (2.2 -16.1 pairs/ 100 km2, Olendorff 1973;Dunkle 1977;Craighead and Mindell 1981;Gilmer and Stewart 1984). Nest availability was sufficiently good on our study area to permit this increase in breeding density, but nest availability did not itself cause this increase in 1986.…”

Nesting Behavior, Provisioning Rates, and Parental Roles of Ferruginous Hawks in New Mexico

“…When the primary prey, black-tailed jackrabbits (Lepus californicus), became rare, remaining ferruginous hawks became nomadic and relocated to more favorable areas to nest (Woffinden and Murphy 1989). This may also explain why other authors have reported dramatic increases over short time periods in the abundance of ferruginous hawks in Alberta (Schmutz 1987b), North Dakota (Gilmer and Stewart 1983), and Wyoming (Platt 1986). …”

“…Although ferruginous hawks tend to avoid cultivated areas for nesting (Olendorff and Stoddart 1974, Blair 1978, Cottrell 1981, Gilmer and Stewart 1983, Schmutz 1984, 1989a, Bechard et al 1990, they can breed successfully in lightly to moderately (less than 10 to 30 percent) cultivated areas. Schmutz (1989a) reported an increasing relationship between ferruginous hawk breeding density and cultivation up to 30 percent; hawk density decreased at cultivation amounts greater than 30 percent.…”

“…woodlands (Jasikoff 1982, Gilmer and Stewart 1983, Olendorff 1993, Bechard and Schmutz 1995. Dense forests, extensive aspen parklands, high elevations, narrow canyons, and habitats recently altered by human development or cultivation are avoided (Janes 1985, Palmer 1988, Black 1992, Olendorff 1993, Bechard and Schmutz 1995.…”

Influence of Poisoned Prey on Foraging Behavior of Ferruginous Hawks

“…However, trembling aspen invasion is not an issue in the drier parts of the Ferruginous Hawk range. A negative relationship between the proportion of land under cultivation and site occupancy by Ferruginous Hawks has been demonstrated many times in several different geographical areas (e.g., Gilmer and Stewart 1983, Woffinden and Murphy 1989, Schmutz 1993, 1994. One reason postulated for this relationship is the fact that Ferruginous Hawks are very sensitive to disturbance during the nesting season.…”