Ferruginous Hawk Natural History Sample Clauses

Ferruginous Hawk Natural History. The ferruginous hawk is a large, broad-winged hawk that nests in flat or rolling terrain in pinyon-juniper, shrublands, and grasslands of the western United States, but rarely nests in forests. Landscapes with less than 50 percent coverage of cropland and hayland are used for nesting and foraging155. Ferruginous hawks use a variety of nesting substrates, most commonly trees and large shrubs, followed by cliffs, utility structures, dirt outcrops, and relatively flat ground156. Historically, ground nesting was common157. They typically build large nests of sticks, twigs and debris and often reuse nests for many years158. In northeastern Wyoming, ferruginous hawks are opportunistic nesters, often selecting nest sites away from golden eagle nests159. Territory and nest site re-occupancy is common for ferruginous hawks and territories often contain multiple alternate nests160. Most breeding ferruginous hawks arrive in Wyoming in April and leave by September161. Ferruginous hawks are easily disturbed during the breeding season, particularly during the early stages of nesting, and sensitivity to disturbance may be heightened during years of low prey abundance162. Average annual clutch size of ferruginous hawks varies from 2 to 4 eggs, but can range from 1 to 8 depending upon prey abundance. The mean number of fledglings produced by a breeding pair each year ranges 150 McDonald et al. (2004) 151 Xxxxx et al. (2003), McDonald et al. (2004) 152 Xxxxx et al. (2003) 153 57 FR 37507 154 USFWS (2004b) 155 Xxxxxxx et al. (1999) 156 Olendorff (1993), Xxxxxxx and Xxxxxxx (1995), Xxxxxxx (2001) 157 CEC (2005b) 158 Xxxxxxx and Xxxxxxx (1995) 159 Xxxxxxxx and Xxxxx (1990) 160 Xxxxxxx et al. (1999) 161 Xxxxxxxx (2000b) 162 Xxxxxxx et al. (1999) from 1.3 to 3.2163. Young typically leave the nest at 38 to 50 days of age, but remain dependent upon the parents for several weeks after fledging164. Ferruginous hawks eat primarily mammals, including rabbits, ground squirrels, prairie dogs, and pocket gophers. Generally, to the east of the Continental Divide the primary prey is prairie dogs and other ground squirrels165. In southern Wyoming, MacLaren et al. (1988) found ferruginous hawks had the most diverse diet when compared to prairie falcons, golden eagles, and red tailed hawks. Ferruginous hawks took 37 percent ground squirrels, 22 percent prairie dogs, and 20 percent leporids. However, leporids actually contributed 48 percent of the biomass consumed as compared to 22 percent fro...