Index of Species Information

WILDLIFE SPECIES:  Buteo regalis


AUTHORSHIP AND CITATION : Tesky, Julie L. 1994. Buteo regalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: []. ABBREVIATION : BURE COMMON NAMES : ferruginous hawk TAXONOMY : The currently accepted scientific name for the ferruginous hawk is Buteo regalis (Gray) [1]. There are no recognized subspecies or races. ORDER : Falconiformes CLASS : Bird FEDERAL LEGAL STATUS : None OTHER STATUS : Information on state- and province-level protection status of animals in the United States and Canada is available at NatureServe, although recent changes in status may not be included.


GENERAL DISTRIBUTION : The ferruginous hawk has the most restricted range of any North American buteo [5]. Its breeding range extends from eastern Washington north to southern Alberta, southern Saskatchewan and Manitoba; east to the Dakotas, Nebraska, Kansas, Oklahoma, and Texas; south to New Mexico and Arizona; and west to California and Oregon [1,5,6,21]. It winters from the central and southern parts of its breeding range south to Mexico [6]. ECOSYSTEMS : FRES21 Ponderosa pine FRES28 Western hardwoods FRES29 Sagebrush FRES30 Desert shrub FRES32 Texas savanna FRES33 Southwestern shrubsteppe FRES34 Chaparral-mountain shrub FRES35 Pinyon-juniper FRES38 Plains grasslands FRES39 Prairie FRES40 Desert grasslands STATES :
BLM PHYSIOGRAPHIC REGIONS : 2 Cascade Mountains 4 Sierra Mountains 5 Columbia Plateau 6 Upper Basin and Range 7 Lower Basin and Range 8 Northern Rocky Mountains 9 Middle Rocky Mountains 10 Wyoming Basin 11 Southern Rocky Mountains 12 Colorado Plateau 13 Rocky Mountain Piedmont 14 Great Plains 15 Black Hills Uplift 16 Upper Missouri Basin and Broken Lands KUCHLER PLANT ASSOCIATIONS : K023 Juniper - pinyon woodland K024 Juniper steppe woodland K031 Oak - juniper woodlands K032 Transition between K031 and K037 K038 Great Basin sagebrush K040 Saltbush - greasewood K041 Creosotebush K042 Creosotebush - bursage K043 Paloverde - cactus shrub K044 Creosotebush - tarbush K053 Grama - galleta steppe K054 Grama - tobosa prairie K055 Sagebrush steppe K056 Wheatgrass - needlegrass shrubsteppe K057 Galleta - three-awn shrubsteppe K058 Grama - tobosa shrubsteppe K059 Trans-Pecos shrub savanna K064 Grama - needlegrass - wheatgrass K065 Grama - buffalograss K066 Wheatgrass - needlegrass K067 Wheatgrass - bluestem - needlegrass K068 Wheatgrass - grama - buffalograss K069 Bluestem - grama prairie K074 Bluestem prairie K075 Nebraska Sandhills prairie K076 Blackland prairie K077 Bluestem - sacahuista prairie K079 Palmetto prairie K086 Juniper - oak savanna K088 Fayette prairie SAF COVER TYPES : 220 Rocky Mountain juniper 222 Black cottonwood - willow 235 Cottonwood - willow 238 Western juniper 239 Pinyon - juniper SRM (RANGELAND) COVER TYPES : NO-ENTRY PLANT COMMUNITIES : The ferruginous hawk inhabits grasslands, sagebrush (Artemisia spp.) scrub, saltbush (Atriplex spp.)-greasewood (Sarcobatus spp.) scrub, and the periphery of pinyon (Pinus spp.)-juniper (Juniperus spp.) and other woodlands [11,21]. The ferruginous hawk is an obligate grassland or desert-shrub nester [26,33]. Ecotones between pinyon-juniper and sagebrush scrub are commonly used by the ferruginous hawk in the semiarid western United States [11].


TIMING OF MAJOR LIFE HISTORY EVENTS : Age at sexual maturity - Most ferruginous hawks become sexually mature at 2 years of age [5]. Breeding season - The ferruginous hawk generally returns to breeding grounds in late March or early April [24] and begin nest construction in April [5]. Breeding pairs aggressively defend their nesting territory. Nests are frequently reused by the same pair in subsequent years [24]. Clutch size and incubation - The ferruginous hawk generally lays three to four eggs in April but this number varies with fluctuating food supply. The eggs are incubated for 28 to 36 days [5,21]. Incubation is shared by both sexes [5,21]. The ferruginous hawk generally will not lay a replacement clutch or renest if disturbed [21]. Fledging - Male nestlings fledge at 38 to 40 days. The females, which are heavier and develop more slowly, fledge about 10 days later [21]. Fall migration - Migration generally begins in late September through early October, with the onset of cold weather [21]. Spring migration - Ferruginous hawks usually arrive in the northern tier of states from late March through early April. The yearling ferruginous hawks arrive in May through early June [21]. Longevity - The maximum potential longevity for the ferruginous hawk is about 20 years [21]. PREFERRED HABITAT : The ferruginous hawk inhabits semiarid to arid western plains and intermountain regions [6]. It occupies open country with scattered trees, primarily prairies, plains, and badlands [1,6]. The ferruginous hawk avoids high elevations, forest interiors, steep, narrow canyons, and high cliffs [12,21]. Nesting habitat - Ferruginous hawk nesting habitat consists of communities with isolated trees, woodland edges, buttes, cliffs, and/or grassland with some relief. Ferruginous hawks generally nest within a short distance of their food supply [11]. Most ferruginous hawk nesting studies report a preference for tree nests [16,20,27]. However, ferruginous hawks will use a wide variety of sites, including riverbed mounds, cutbanks, small hills, small cliffs, powerline structures, and haystacks [6]. Tree nests are usually in the upper canopy, from 6 to 55 feet (2-17 m) above the ground [6]. The nest tree is typically isolated or is in an isolated small cluster of trees in an exposed location. Juniper is the most commonly used tree for nesting, but pine (Pinus spp.), willow (Salix spp.), cottonwood (Populus spp.), swamp oak (Quercus spp.), and sagebrush have been used [16,21]. In northern Utah and southeastern Idaho, Howard and Wolfe [10] reported that Utah juniper (Juniperus osteosperma) provided sites for 95 percent of the observed ferruginous hawk nests. Desert shrub types and Fairway wheatgrass (Agropyron cristatum)-seeded areas comprised the dominant vegetation around nest sites [10]. Of the active ferruginous hawk nests in the Centennial Valley of the Greater Yellowstone Ecosystem, 70 percent were in willows along streams [5]. Ferruginous hawks will nest in trees and large shrubs along the edge of forests and wooded areas that are adjacent to open areas [11]. Ground nests tend to be on slopes, knolls, and crests of ridges, often on or lodged between boulders [21]. The ferruginous hawk will accept both modified and completely artificial nest structures. Use of artificial structures for nesting appears to occur most often when natural nesting substrates are scarce or unavailable [11]. Of 71 ferruginous hawk nests on the plains of Colorado, 69 percent were in trees, 11.3 percent on erosional remnants, 5.6 percent on the ground, 5.6 percent on cliffs, 5.6 percent on creekbanks, and 2.9 percent on artificial structures [20]. Ground nests in southern Idaho were constructed in areas of rangeland where no suitable nest trees were available. They were usually located near a small hill [11]. In Campbell and Converse counties, Wyoming, the majority of ferruginous hawk nests were built on the ground, usually on a fairly prominent rock, eroded creekbank, or sandstone or scoria outcrop. Ground nests were often built in new locations in successive years [22]. Foraging habitat - The ferruginous hawk generally forages in open habitats with short vegetation containing abundant prey [11,12]. The best habitat is occupied by high quality prey on over 75 percent of the home range. This estimate is based on data that indicate that ferruginous hawks generally hunt over large portions of their home range. High quality food is not required over 100 percent of the area because the effective hunting range is usually smaller than the home range. Food suitability for the ferruginous hawk is optimum when the vegetation occurs at a mix of heights and densities which optimizes prey abundance and minimizes hunting interference [11]. The ferruginous hawk hunts mainly in early morning and late afternoon from low flights and perches [5]. Winter habitat - The ferruginous hawk inhabits open terrain from grasslands to deserts during migration and winter. It is the most common wintering buteo on wide expanses of treeless terrain [21]. COVER REQUIREMENTS : Wooded foothills interspersed with valleys and large desert expanses provide optimal nesting sites for the ferruginous hawk because of the combination of human inaccessibility and ease of surveillance of the surrounding area. Tree nests are often exposed, providing protection from ground predators and shade for nestlings [11]. Ground nests are concealed. In South Dakota, ground nests were always located in prairies with tall herbaceous cover or prairies that were in a lightly grazed condition [16]. On the plains of Colorado, ferruginous hawks used fenceposts, telephone poles, and dead trees as perch sites [11]. FOOD HABITS : The ferruginous hawk feeds primarily on rabbits (Lepus spp. and Sylvilagus spp.), ground squirrels (Spermophilus spp.), and prairie dogs (Cynomys spp.), but also takes mice, rats, gophers, birds, snakes, locusts, and crickets [6,11,21]. Analysis of prey items collected from nests indicate that jackrabbits (Lepus spp.) often constitute the most important prey item based on biomass [10,23,27,31,33]. A central Utah study reported that black-tailed jackrabbits (Lepus californicus) made up more than 95 percent of ferruginous hawk prey biomass [33]. Significant fluctuations in ferruginous hawk densities may be an indication of the abundance and diversity of prey species. A decline in ferruginous hawk numbers in Utah was directly correlated with a drop in the jackrabbit population [11]. Ferruginous hawk fledgling success and nesting densities in southern Idaho and northern Utah were closely correlated with the cyclic black-tailed jackrabbit population [28]. However, in years of low prey abundance, ferruginous hawks will often switch from primary to alternate prey [21,32]. The nesting success of some populations of ferruginous hawks in Utah, where jackrabbit numbers declined dramatically, was attributed to the presence of a broad prey base [32]. PREDATORS : Golden eagles (Aquila chrysaetos), prairie falcons (Falco mexicanus), great horned owls (Bubo virginianus), coyotes (Canis latrans) and red foxes (Vulpes vulpes) are predators of ferruginous hawk eggs and nestlings [29]. MANAGEMENT CONSIDERATIONS : The ferruginous hawk requires large tracts of relatively undisturbed areas [5]. The conversion of extensive tracts of native vegetation into monotypic stands for grazing and agriculture may reduce ferruginous hawk densities and reproductive success. Reductions may be due to decreased availability of major prey, loss of nest sites, and increased human disturbance [3,10,11]. The ferruginous hawk is vulnerable to tree removal. Peripheral trees should be left during tree removal and chaining operations to provide nest sites. Isolated trees can be protected by fenced enclosures. Loss of isolated trees can be remediated by artificial nest structures [11]. Maximum consideration should be afforded this species when range development is planned [3]. Land management practices that dramatically alter the density and structure of native vegetation can adversely affect both jackrabbit and alternate prey populations, resulting in a reduction in breeding ferruginous hawks. Range management practices that support abundant and diverse prey may provide suitable food alternatives for the ferruginous hawk during periods of jackrabbit decline [11]. Conversion of extensive tracts of brushland and native vegetation to either agriculture or monotypic fields of grass is particularly disruptive to jackrabbits and cottontails [11,33]. Areas providing an interspersion of tall cover and open spaces are preferred by jackrabbits. Moderate amounts of rangeland and agricultural land support pocket gophers and ground squirrels, which may provide alternate prey species for the ferruginous hawk [11]. Although overgrazed areas may temporarily provide vulnerable prey, it is unlikely that such areas will support an adequate prey base for any length of time [11]. Additionally, severe overgrazing could affect ferruginous hawk nest site selection by causing a decline in the regeneration of willows [5]. Vegetation management for the ferruginous hawk should emphasize maximizing the amount of edge and interspersion of shrublands and grasslands. Where Fairway wheatgrass plantings are planned, a minimum of 20 percent of the area should be left in scattered islands of shrubby vegetation. This design can produce optimum habitat for the ferruginous hawk within 3 or 4 years after treatment [10]. The ferruginous hawk is very sensitive to human disturbance during the nesting season and may abandon a nest during the pre-egg laying period and incubation even if it is disturbed only once [5,11]. It is important to time the implementation of range improvement activities to avoid nesting periods. Late summer and fall are the optimum seasons for range improvement practices in areas containing nests [3]. It is also important to avoid range improvement activities in areas of high ferruginous hawk foraging use [3,10].


DIRECT FIRE EFFECTS ON ANIMALS : Fire has the potential to adversely affect ferruginous hawk reproductive success if the fire is intense enough to destroy nest trees. Light winter burning probably does no substantial harm [14]. Severe fires or fire suppression efforts during the nesting season may cause ferruginous hawks to abandon their nests. HABITAT RELATED FIRE EFFECTS : The ferruginous hawk occurs in the following major fire-dependent plant associations in the western United States: grassland, semidesert grass-shrub, sagebrush-grass, and pinyon-juniper [15]. In addition to potentially affecting nest trees, fire may affect the prey base and hunting efficiency of ferruginous hawks. Many ferruginous hawk prey species are affected by any disturbance that changes the balance between understory cover and forage. Regular burning helps to keep habitats in a suitable condition for many prey species of the ferruginous hawk and temporarily exposes the prey when cover is reduced [14]. In the past, fires have contributed to the maintenance of grasslands by retarding woody growth. The exclusion of fire in this ecosystem has resulted in encroachment of trees and shrubs which has had a negative affect on the ferruginous hawk [15,21]. Ferruginous hawks are favored by fires that reduce pinyon-juniper woodlands. Removing some of these trees enhances the prey base by improving habitat for small mammals [10]. Additionally, fires may remove thickets that limit the hunting efficiency of ferruginous hawks [14]. Low-severity fires may thin nest trees and enhance hunting nearby. FIRE USE : Prescribed fire can be beneficial to ferruginous hawk populations by providing an increased prey base of species that use burned areas [3,10,14].


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