Widespread and relatively common in appropriate habitats, namely relatively intact native grasslands and shrubsteppe. Reports of local declines, continued loss of habitat, sensitivity to disturbance in a prairie species, and relatively low numbers show this species should be carefully watched and regularly re-evaluated.
occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Breeding
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: (20,000 to >2,500,000 square km (about 8000 to >1,000,000 square miles)) BREEDING: eastern Washington, southern Alberta, southern Saskatchewan, extreme southwestern Manitoba (Bechard and Schmutz 1995), south to eastern Oregon, Nevada, northern Arizona, northern New Mexico, Texas panhandle, extreme western Oklahoma, and western Kansas. Recently discovered breeding in California (Small 1994). Historic breeding range in the southwestern U.S. apparently was much greater than at present (Hall et al. 1988). Two subpopulations are recognized (Bechard and Schmutz 1995); one to the east and another to the west of the Rocky Mountains. NON-BREEDING: primarily southwestern and south-central U.S. south to Baja California and central mainland of Mexico; in the U.S., in largest numbers in western Texas, eastern New Mexico, and western Oklahoma (Root 1988). Winters locally in some more northerly breeding areas (Bechard and Schmutz 1995).
buteo . 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
Regional Distribution in the Western United States
This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):
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
Occurrence in North America
The Ferruginous Hawk can be found in North America, as far north as Canada, south through western and central United States to northern Texas. It winters south to northern Mexico (del Hoyo, et. al. 1940).
Biogeographic Regions: nearctic (Native )
Ferruginous Hawks are usually between 50-66cm (20-26 in.) in length, have an average wingspan of 134-152cm (53-60 in.) and weigh 980-2030g (2.2-4.5 lb.). They are the largest hawks in North America, and are sexually dimorphic. The female hawk may be up to one-and-a half times larger than the male. "Ferruginous" is derived from the Latin Ferrugo, meaning, "rust", which is the predominant color of this hawk. Adults have a rusty color on their back and shoulders, which extends downward onto the legs. The under-part is a whitish color spotted with rufous. A view of the bird in flight will show that the leg feathers form a V shape against the belly of the hawk. When perched, the gray tips of the hawk's long and broad wings often reach the tip of their white, rust, and gray colored tail. Juvenile Ferruginous Hawks lack the rust colored legs and have less color on their backs (Malik 1987; Clark 1987).
Range mass: 980 to 2030 g.
Other Physical Features: endothermic ; bilateral symmetry
Length: 58 cm
Weight: 1231 grams
Dark phase differs from dark-phase rough-legged hawk (BUTEO LAGOPUS) by absence of dark tail bands in the former. Immature resembles Great Plains form of red-tailed hawk (BUTEO JAMAICENSIS) but has larger white wing patches and lacks dark bar on leading edge of underwing (NGS 1983).
The Ferruginous Hawk is most often found in the interior in lowlands, plateaus, valleys, plains, rolling hills of grass land, agricultural land, ranches, and the edges of deserts (Clark 1987).
Terrestrial Biomes: desert or dune ; savanna or grassland ; chaparral
Habitat and Ecology
Comments: Open country, primarily prairies, plains and badlands; sagebrush, saltbush-greasewood shrubland, periphery of pinyon-juniper and other woodland, desert. In the southern Great Plains, common at black-tailed prairie dog colonies in winter (Schmutz and Fyfe 1987). Nests in tall trees or willows along streams or on steep slopes, in junipers (Utah), on cliff ledges, river-cut banks, hillsides, on power line towers, sometimes on sloped ground on the plains or on mounds in open desert. Generally avoids areas of intensive agriculture or human activity.
Prefer open grasslands and shrubsteppe communities. Uses native and tame grasslands, pastures, hayland, cropland, and shrubsteppe (Stewart 1975, Woffinden 1975, Powers and Craig 1976, Fitzner et al. 1977, Blair 1978, Wakeley 1978, Lardy 1980, Schmidt 1981, Gilmer and Stewart 1983, Green and Morrison 1983, Konrad and Gilmer 1986, MacLaren et al. 1988, Palmer 1988, Roth and Marzluff 1989, Bechard et al. 1990, Black 1992, Niemuth 1992, Bechard and Schmutz 1995, Faanes and Lingle 1995, Houston 1995, Zelenak and Rotella 1997, Leary et al. 1998). Usually occupy rolling or rugged terrain (Blair 1978, Palmer 1988, Black 1992). High elevations, forest interiors, narrow canyons, and cliff areas are avoided (Janes 1985, Palmer 1988, Black 1992), as is parkland habitat in Canada (Schmutz 1991a).
Landscapes with moderate coverage (less than 50 percent) of cropland and hayland are used for nesting and foraging (Blair 1978; Wakeley 1978; Gilmer and Stewart 1983; Konrad and Gilmer 1986; Schmutz 1989, 1991a; Bechard et al. 1990; Faanes and Lingle 1995; Leary et al. 1998). In North Dakota, hayfields and native pastures were the habitats most often used by both fledglings and adults, whereas cultivated fields rarely were used (Konrad and Gilmer 1986). Fledglings in South Dakota hunted in an area where native hay recently had been cut (Blair 1978). When prey densities were low in big sagebrush (Artemisia tridentata)/grassland habitat, agricultural fields served as important foraging areas (Leary et al. 1998). Foraged extensively in alfalfa (Medicago sativa) and irrigated potato fields in Washington and in alfalfa fields in Idaho during the breeding season presumably because of high prey densities (Wakeley 1978, Leary et al. 1998).
Nest site selection depends upon available substrates and surrounding land use. Ground nests typically are located far from human activities and on elevated landforms in large grassland areas (Lokemoen and Duebbert 1976, Blair 1978, Blair and Schitoskey 1982, Gilmer and Stewart 1983, Atkinson 1992, Black 1992). Lone or peripheral trees are preferred over densely wooded areas when trees are selected as the nesting substrate (Weston 1968, Lokemoen and Duebbert 1976, Gilmer and Stewart 1983, Woffinden and Murphy 1983, Palmer 1988, Bechard et al. 1990). Tree-nesting hawks seem to be less sensitive to surrounding land use, but they still avoid areas of intensive agriculture or high human disturbance (Gilmer and Stewart 1983; Schmutz 1984, 1987, 1991a; Bechard et al. 1990).
In eastern Colorado, nested more frequently in grassland areas than in cultivated areas (Olendorff 1973). In North Dakota, preferred to nest in areas dominated by pasture and hayland (Gilmer and Stewart 1983, Gaines 1985). In southwestern Montana, sagebrush (Artemisia) and grasslands predominated within 100 meters of nests (Atkinson 1992). Ground nests in northern Montana were located in grass-dominated, rolling (more than 10 percent slope) rangeland; in general, cropland and areas with dense (more than 30 percent cover), tall (more than 15.24 centimeters) sagebrush were avoided (Black 1992). In western Kansas, most nests were surrounded by more than 50 percent rangeland and 25-50 percent cropland, although one pair incorporated more than 75 percent cropland in its territory (Roth and Marzluff 1989). The majority of nests (86 of 99) were not in direct view of black-tailed prairie dog (Cynomys ludovicianus) towns, although most nest sites were within 8 kilometers of towns (Roth and Marzluff 1989). In Utah, Idaho, Oregon, and California, preferred native grassland and shrubland habitats over cropland, and preferred areas with no perches (Janes 1985). In Washington, some nests occurred in agricultural fields, but most nests were in areas with higher percentages of grassland, shrubland, and western juniper (Juniperus occidentalis) (Bechard et al. 1990). Nest productivity in Idaho was greater in territories with higher amounts of crested wheatgrass (Agropyron cristatum) fields interspersed with desert shrub than in territories with monotypic stands of crested wheatgrass or shrubland, or with greater amounts of Utah juniper (Juniperus osteosperma), alfalfa, and cropland (Howard 1975). In Nevada, open, rolling sagebrush near the pinyon-juniper interface is the preferred landscape for breeding Ferruginous Hawks (GBBO 2010).
In Alberta, however, cultivated areas (11-30 percent of 4,100 hectare plots) had higher nesting densities than grassland areas with 0-11 percent cultivation (Schmutz 1989). In cultivated areas (20 percent) in northcentral Montana, nests closer to cultivated fields and roads were more successful, presumably because of higher prey densities associated with edge habitats (Zelenak and Rotella 1997). The numbers of fledglings produced in unfragmented rangeland versus a mixture of rangeland and cropland were not significantly different in Nebraska (Podany 1996).
The slope, height, and exposure of nests were mostly similar across the species' range. The mean height of ground nests (on buttes or hills) above the surrounding prairie in South Dakota was less than 10 meters, and nests were oriented toward the south and west, providing access to prevailing winds from the south and west (Blair 1978). Lokemoen and Duebbert (1976) found ground nests in South Dakota were all oriented toward the west. Nests in southwestern Montana were significantly oriented toward the south (Atkinson 1992). Nests on rock outcrops in Montana were built on slopes averaging 62.8 percent and were found on the upper 35 percent of the slope (Atkinson 1992). Ground nests in northern Montana were located either on the top of a small rise or on slopes ranging from 10 to 50 percent (Black 1992). Average height of ground nests below the highest surrounding topographic feature was 10 meters, whereas average height of ground nest sites above the valley floor was 10.4 meters, indicating that nests were placed at mid-elevation sites within the immediate topography (Black 1992). Nests in Wyoming were built on a mean slope of 14.26 degrees, and the mean height of nests was 4.55 meters (MacLaren et al. 1988). In southeastern Washington, 86 percent of nests on outcrops and in western junipers were located less than 10 meters from the ground and had southern or western exposures (Bechard et al. 1990). In Oregon shrubsteppe, nests were in relatively short western juniper trees, were less than 10 meters from the ground, and had large support branches (Green and Morrison 1983). In Washington, Idaho, and Utah, the majority of nests also were less than 10 meters from the ground in western juniper and Utah juniper trees (Woffinden 1975, Fitzner et al. 1977, Woffinden and Murphy 1983). Howard (1975) and Howard and Wolfe (1976) also found Utah juniper trees were important nest substrates in southern Idaho and northern Utah. In Utah, nests were built 2-3 meters from the ground, were most commonly located on the sides or summits of hills, and often had southern or eastern exposures (Weston 1968). Woffinden (1975) found that the majority of nests in Utah were on slopes ranging from 15 to 80 degrees with a mean of 42.5 degrees.
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 . 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 . On the plains of Colorado, ferruginous hawks
used fenceposts, telephone poles, and dead trees as perch sites .
The ferruginous hawk inhabits semiarid to arid western plains and
intermountain regions . 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 . 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
Tree nests are usually in the upper canopy, from 6 to 55 feet (2-17 m)
above the ground . 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  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 . Of the active ferruginous hawk nests in the Centennial
Valley of the Greater Yellowstone Ecosystem, 70 percent were in willows
along streams . Ferruginous hawks will nest in trees and large
shrubs along the edge of forests and wooded areas that are adjacent to
open areas .
Ground nests tend to be on slopes, knolls, and crests of ridges, often
on or lodged between boulders . 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 .
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 . 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 . 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 .
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 . The ferruginous hawk
hunts mainly in early morning and late afternoon from low flights and
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 .
Habitat: Plant Associations
This species is known to occur in association with the following plant community types (as classified by Küchler 1964):
More info for the terms: cactus, shrub
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
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
This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):
FRES21 Ponderosa pine
FRES28 Western hardwoods
FRES30 Desert shrub
FRES32 Texas savanna
FRES33 Southwestern shrubsteppe
FRES34 Chaparral-mountain shrub
FRES38 Plains grasslands
FRES40 Desert grasslands
Associated Plant Communities
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 .
Habitat: Cover Types
This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):
220 Rocky Mountain juniper
222 Black cottonwood - willow
235 Cottonwood - willow
238 Western juniper
239 Pinyon - juniper
Non-Migrant: No. All populations of this species make significant seasonal migrations.
Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.
Arrives in northern breeding range (South Dakota) by March-early April, in Utah and Colorado mostly in late February-early March; yearlings arrive later. Adults depart northern end of breeding range by late October; young depart in August. Wintering areas of grassland and desert shrub breeders are mainly separate. (Schmutz and Fyfe 1987). Alberta populations winter mainly in Texas. In southern breeding range, may be short-distance migrant or possibly sedentary (Palmer 1988).
it breeds in canada,washington,idaho and north dakota.
Ferruginous Hawks are carnivorous. They commonly hunt by flying low to the ground over open fields at high speeds, soaring high above, hovering, or swooping down from perches. Hawks use their excellent eyesight to spot their prey on the ground and then attack with talons. Ground squirrels, jackrabbits, and mice, as well as birds, reptiles, and amphibians are common prey for this hunter. Depending on the size of the prey, Ferruginous Hawks will swallow it whole, or tear off pieces of the animal with its beak. The portion of the food that can not be digested is then regurgitated into a food pellet (Zeiner 1990; Clark 1987).
Comments: Mammals are the primary prey during the breeding season, although birds, amphibians, reptiles, and insects also are taken (Weston 1968, Howard 1975, Fitzner et al. 1977, Blair 1978, Smith and Murphy 1978, Gilmer and Stewart 1983, Palmer 1988, De Smet and Conrad 1991, Atkinson 1992). Primary prey in central grasslands are ground squirrels (SPERMOPHILUS SPP.), followed by pocket gophers (THOMOMYS SPP.) and white-tailed jackrabbits (LEPUS TOWNSENDII) (Bechard and Schmutz 1995). Primary prey in western shrubsteppe are jackrabbits (LEPUS SPP.), followed by ground squirrels and pocket gophers (Smith and Murphy 1978, Bechard and Schmutz 1995). White-tailed (CYNOMYS LEUCURUS) and black-tailed prairie dogs(CYNOMYS LUDOVICIANUS)also serve as prey items (Powers and Craig 1976, MacLaren et al. 1988).
In Oregon, Janes (1985) found that the highest abundance of major prey species (white-tailed jackrabbits, Townsend's ground squirrels [SPERMOPHILUS TOWNSENDII], and northern pocket gophers [THOMOMYS TALPOIDES]) occurred in native grasslands.
Vulnerability of prey also is an important factor in habitat suitability, such that Ferruginous Hawks avoid dense vegetation that reduces their ability to see prey (Howard and Wolfe 1976, Wakeley 1978, Schmutz 1987). Prey vulnerability decreases where taller small-grain crops replace shorter grasses (Houston and Bechard 1984). Intensive agricultural practices, such as annual plowing and biennial fallowing, exclude many prey species (Wakeley 1978, Houston and Bechard 1984). In Alberta, prey abundance increases as the area of cultivation increases up to 30 percent, but abundance is reduced where agriculture is extensive, e.g., more than 30 percent (Schmutz 1989).
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 .
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 . Ferruginous hawk fledgling success and
nesting densities in southern Idaho and northern Utah were closely
correlated with the cyclic black-tailed jackrabbit population .
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
great horned owls (Bubo virginianus), coyotes (Canis latrans) and red
foxes (Vulpes vulpes) are predators of ferruginous hawk eggs and
Known prey organisms
Based on studies in:
USA: California, Cabrillo Point (Grassland)
This list may not be complete but is based on published studies.
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 81 to >300
Comments: Probably in the low hundreds, however, until new EOSPECs are put in use, or more nests areas mapped, this is uncertain.
10,000 to >1,000,000 individuals
Comments: Most recent population estimate is 5,842-11,330 compiled by Olendorff (1993). However, Schmutz et al. (1992) estimated 14,000 for the Great Plains alone. Estimated population in Canada in the early 1990s was 2000-4000 breeding pairs (Schmutz, 1994 COSEWIC report, cited by Jensen 1995). Between year movements of population centers and individuals makes estimation of actual abundance difficult.
Density and productivity are closely associated with cycles of prey abundance (Woffinden 1975; Powers and Craig 1976; Smith and Murphy 1978, Smith et al. 1981; Gilmer and Stewart 1983; Houston and Bechard 1984; White and Thurow 1985; Palmer 1988; Schmutz 1989, 1991a; Schmutz and Hungle 1989; Bechard and Schmutz 1995). Estimates of home range size vary from 3.14 to 8.09 square kilometers in the Columbia River Basin and Great Basin regions of the western U.S. (Janes 1985). The average home range was 90.3 square kilometers in Washington, and the variability in home range was significantly related to distance from the nest to the nearest irrigated agricultural field (Leary et al. 1998). One male that nested closest to the surrounding agricultural fields had the smallest home range, whereas another male nesting farthest from the agricultural fields had the largest home range. In Utah, mean home range recorded of 5.9 square kilometers (Smith and Murphy 1973). An area of up to 21.7 square kilometers may be required by one pair for hunting in Idaho (Wakeley 1978). Up to 8-10 nests per 100 square kilomters if local conditions are favorable (see Palmer  for density data in several areas). In 11 study areas, mean nearest neighbor distance was 3.4 kilometers (range 0.8-7.2); in six study areas the mean home range size was 7.0 square kilometers (range 3.4-21.7) (Olendorff 1993). Recent studies in Idaho (McAnnis 1990) and Washington (Leary 1996) found average home ranges of 7.6 square kilometers (minimum convex polygon)/19.4 square kilometers (95 percent harmonic mean) and 70 square kilometers (95 percent minimum convex polygon)/31 square kilometers (85 percent adaptive kernel), respectively.
First year mortality generally is around 66 percent in the Great Plains region (Schmutz and Fyfe 1987).
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 .
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
. 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 . Additionally, fires may remove thickets that limit
the hunting efficiency of ferruginous hawks . Low-severity fires
may thin nest trees and enhance hunting nearby.
Timing of Major Life History Events
at 2 years of age .
Breeding season - The ferruginous hawk generally returns to breeding
grounds in late March or early April  and begin nest construction in
April . Breeding pairs aggressively defend their nesting territory.
Nests are frequently reused by the same pair in subsequent years .
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 .
Fledging - Male nestlings fledge at 38 to 40 days. The females, which
are heavier and develop more slowly, fledge about 10 days later .
Fall migration - Migration generally begins in late September through
early October, with the onset of cold weather .
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 .
Longevity - The maximum potential longevity for the ferruginous hawk is
about 20 years .
Life History and Behavior
Perception Channels: visual ; tactile ; acoustic ; chemical
Comments: Hunts most frequently near sunrise and sunset (Evans 1982).
Status: wild: 20 (high) years.
Status: wild: 284 months.
Lifespan, longevity, and ageing
Ferruginous Hawks tend to breed in open territory, plains, prairies, and badlands. Nests are built on low cliffs, buttes, cut banks, shrubs, or trees, and occasionally on man-made structures or the ground. Sticks 2.5cm (1in.) in diameter, cow dung, bones, and grass are used in construction of nests. Ferruginous Hawks have a clutch of 2-6 eggs that are bluish white, marked with brown. The average size of the egg is 2.4" (61mm). The eggs are fertilized and laid in April, and incubate for approximately 28 days. Young fledge within 38-50 days. The parents share the responsibility of feeding the young until they become independent, usually after 30 to 60 days (Ehrich 1988; Clark 1987).
Key Reproductive Features: iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
Average time to hatching: 32 days.
Average eggs per season: 3.
Average age at sexual or reproductive maturity (male)
Sex: male: 730 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 730 days.
Occur on breeding areas from late February through early October (Weston 1968, Olendorff 1973, Maher 1974, Blair 1978, Smith and Murphy 1978, Gilmer and Stewart 1983, Schmutz and Fyfe 1987, Palmer 1988, Bechard and Schmutz 1995). See Palmer (1988) and Hall et al. (1988) for egg dates in different areas. Clutch size usually is two to four. Incubation lasts about 32-33 days, mostly by female; male provides food. Young fledge in 35-50 days (males before females), depend on parents for several weeks more. No evidence that yearlings breed. Renesting within the same year is rare (Woffinden 1975, Palmer 1988) even when clutch is lost. Territory and nest site reoccupancy is common and one of several nests within a territory may be used in alternate years (Davy 1930, Weston 1968, Olendorff 1973, Blair 1978, Smith and Murphy 1978, Palmer 1988, Roth and Marzluff 1989, Schmutz 1991b, Atkinson 1992, Houston 1995). Mate fidelity also is common. (Schmutz 1991b). Clutch size, fledging rate, and/or breeding density tend to vary with prey (especially jackrabbit [LEPUS SPP.] or ground squirrel [SPERMOPHILUS SPP.]) availability.
Molecular Biology and Genetics
Barcode data: Buteo regalis
Below is the sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen.
Other sequences that do not yet meet barcode criteria may also be available.
-- end --
Download FASTA File
Statistics of barcoding coverage: Buteo regalis
Public Records: 1
Specimens with Barcodes: 2
Species With Barcodes: 1
Human agriculture and overgrazing have caused a great deal of disturbance in this hawk's nesting habitat. Many of these hawks have been shot while perched along roadsides. Federal law now protects all raptors, yet Ferruginous Hawks are still a species of special concern. In Washington Ferruginous Hawks are listed as Threatened (Leary 1998; Enrich 1988). They are also listed as near threatened by the IUCN.
US Migratory Bird Act: protected
US Federal List: no special status
CITES: appendix ii
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
IUCN Red List Assessment
Red List Category
Red List Criteria
National NatureServe Conservation Status
Rounded National Status Rank: N4B - Apparently Secure
Rounded National Status Rank: N4B,N4N : N4B: Apparently Secure - Breeding, N4N: Apparently Secure - Nonbreeding
NatureServe Conservation Status
Rounded Global Status Rank: G4 - Apparently Secure
Reasons: Widespread and relatively common in the appropriate habitat. Reports of local declines, continued loss of habitat, sensitivity to disturbance in a prairie species, and relatively low numbers show this species should be carefully watched and regularly re-evaluated.
United States and Canada is available at NatureServe, although recent
changes in status may not be included.
Global Short Term Trend: Relatively stable (=10% change)
Comments: Local declines have been noted (e.g., Woffinden and Murphy 1989), but a widespread decline was not evident as of the early-1990s (USFWS 1992, Olendorff 1993). North American Breeding Bird Survey (BBS) data for the U.S. and Canada indicate a 13.5 percent increase from 1988 to 1989 and an average annual 0.5 percent increase for 1966-1989 (Droege and Sauer 1990). Wintering data from Christmas Bird Counts also indicate an increase in numbers from 1952-1984 (USFWS 1992). Schmutz (1995) reported that the range in Canada has been reduced by half, and that habitat within the range has been severely depleted and total numbers reduced by about 95 percent. Kirk et al. (1995) indicated that populations in Canada apparently are stable in available habitat. Jensen (1995) reported a recent range re-expansion in south-central Canada. Historically, very abundant in eastern Montana but numbers were lowered by the early 1900's (Allen 1874, Cameron 1914).
Degree of Threat: B : Moderately threatened throughout its range, communities provide natural resources that when exploited alter the composition and structure of the community over the long-term, but are apparently recoverable
Comments: HABITAT LOSS: Some habitat has been lost due to agricultural development. Schmutz and Schmutz (1980) reported that habitat in the breeding range in Canada has been severely depleted by agriculture, disturbance, and forest invasion (see also Jensen 1995), though recent trends suggest relative stability (Schmutz 1995). Loss of grassland is not regarded as an immediate threat (USFWS 1992), but is likely a long-term threat (Olendorff 1993). Ability of native grasslands and shrublands to support viable populations may be compromised by the invasion of exotic annuals, especially cheatgrass (BROMUS TECTORUM) and Russian thistle (SALSOLA IBERICA). However, conversion of large areas of dense shrublands to grasslands may locally benefit Ferruginous Hawks. HUMAN DISTURBANCE: Easily disturbed during the breeding season (Olendorff 1973, Gilmer and Stewart 1983, Schmutz 1984, White and Thurow 1985, Bechard et al. 1990). Abandonment of nests occurs particularly in the early stages of nesting (Davy 1930, Weston 1968, Fitzner et al. 1977, Gilmer and Stewart 1983, White and Thurow 1985). In eastern Colorado, nests in remote locations had greater productivity compared to more accessible nests (Olendorff 1973). In South Dakota, the probability of fledging young was 11.4 percent greater in more remote nests than in nests within 2.47 kilometers of occupied buildings (Blair 1978). In North Dakota, avoided cropland and nesting within 0.7 kilometers of occupied buildings (Gaines 1985). In Alberta, rarely nested within 0.5 kilometers of farmyards (Schmutz 1984). In other instances, more tolerant of human disturbance. Nesting has occurred near active railroads and gravel roads (Rolfe 1896, Gilmer and Stewart 1983, MacLaren et al. 1988). Sensitivity to disturbance may be heightened in years of low prey abundance (White and Thurow 1985). Shooting may also be a threat, especially on the wintering grounds (Harmata 1981, Gilmer et al. 1985). Poisoning of prey species may be a threat both directly to hawks eating poisoned animals and indirectly through reduction of prey base, especially at prey concentration areas such as prairie dog colonies. Noted as an accidental but unsuitable host of the Brown-headed Cowbird (MOLOTHRUS ATER), an obligate brood parasite (Friedmann 1963).
CITES Appendix II. CMS Appendix II.
Preserve Selection and Design Considerations: LAND PROTECTION: Maintain ownership of public lands that have substantial numbers of hawks (Olendorff 1993). Protect large tracts of native prairie from conversion to monotypic stands of grass or other types of agriculture (Howard and Wolfe 1976, Lardy 1980, Schmutz 1991a, Bechard and Schmutz 1995). Avoid seeding of exotic grasses and cultivating of habitat, where possible (Janes 1985). Leave scattered islands of shrubby vegetation in crested wheatgrass fields so that the islands make up a minimum of 20 percent of the total area (Howard and Wolfe 1976).
Management Requirements: PREY CONSIDERATION: Increase grassland area to increase Richardson's ground squirrel (SPERMOPHILUS RICHARDSONII) abundance in Canada (Houston and Bechard 1984). Improve prey habitat by providing native shrub vegetation and increasing edge (Howard and Wolfe 1976, Bechard and Schmutz 1995). If brush is chained, windrow it to provide cover for prey (Olendorff 1993). When converting land from sagebrush steppe to herbaceous grassland (e.g., to crested wheatgrass), create a mosaic of treated (chained or disced) and untreated areas (Howard and Wolfe 1976). To attract small rodents, maintain or restore sagebrush-grass rangeland, removing pinyon pine (PINUS EDULUS)/Utah juniper stands (Howard and Wolfe 1976). If it is necessary to control lagomorph or rodent populations, try to lower the peaks of cyclic highs rather than completely exterminating them (Olendorff 1993).
REDUCE DISTURBANCE: Do not disturb nest sites from 15 March to 15 July (Howard and Wolfe 1976, Bechard and Schmutz 1995). Close public areas near nest sites to recreation during the breeding season (Lardy 1980) and close public land to firearms where dense populations of Ferruginous Hawks are particularly susceptible to shooting (Olendorff 1993). Establish buffer zones around nest sites and delay energy development until 45 days after fledging (Konrad and Gilmer 1986). White and Thurow (1985) recommended creating a buffer zone of 0.25 kilometers around nest sites. Atkinson (1992) suggested that a minimum distance of 0.45 kilometers be maintained from the nest. Olendorff (1993) suggested buffer zones of 0.25 kilometers for brief disturbances, 0.5 kilometers for intermittent activities, 0.8 kilometers for prolonged activities, and more than 1.0 kilometer for construction or similar activities. Provide information to ranchers, seismic crews, prospectors, and others to avoid disturbance to the nest (Atkinson 1992). Conduct treatments, e.g., chaining, discing, plowing, or burning, during the non-nesting season to avoid direct impacts to the hawks and their prey species during the reproductive season (Olendorff 1993). Generally, avoid treatments between 1 March and 1 August each year, especially during the incubation period when hawks are more prone to abandon nests if disturbed. Mitigate development impacts from mining, pipeline construction, and urbanization (Bechard and Schmutz 1995). Encourage rest-rotation or deferred-rotation grazing systems (Olendorff 1993). Delay grazing to allow for the completion of incubation (Atkinson 1992).
NEST STRUCTURES: Enhance, protect, and create nest substrates through fencing of nest trees, supporting heavy tree nests that are at risk of toppling, and building artificial nesting structures where nest sites are otherwise lacking (Olendorff 1973, Smith and Murphy 1978, Houston 1985, Bechard and Schmutz 1995, Leary et al. 1998). Other successful nest structure management techniques are to remove some of the previous year's nesting material to reduce the chance of toppling, realign the nest over a vertical axis, widen the base of the nest, reinforce the base of the nest using wire netting or other materials, move the nest to a safer location, or provide protection from predators by nailing tin sheathing around the tree base (Craig and Anderson 1979). In converting tree communities to grassland, provide nest sites by leaving individual trees, a mosaic of stands of trees, or a thin scattering of trees (Olendorff 1993). Leave poles and cross-arms of unused electrical lines for hunting perches (Olendorff 1993).
GRAZING: Grazing provides benefits by reducing vegetative cover and making prey more visible (Wakeley 1978, Konrad and Gilmer 1986). Kantrud and Kologiski (1982) found highest densities of Ferruginous Hawks in heavily grazed areas in the northern Great Plains. These areas provided a combination of grazing and soil type (typic borolls) that resulted in abundant prey populations (Kantrud and Kologiski 1982). In South Dakota, preferentially placed ground nests in lightly grazed pasture or idle areas (Lokemoen and Duebbert 1976, Blair 1978, Blair and Schitoskey 1982). In Saskatchewan, preferred grassland habitat exists in large blocks of government pastures located along the Montana and Alberta borders (Houston and Bechard 1984). These blocks of habitat are the only remaining areas with stable populations in Saskatchewan (Houston and Bechard 1984). Livestock, however, can weaken nest trees by excessive rubbing or trampling (Houston 1982, Olendorff 1993). Bock et al. (1993) suggested negative response to grazing in shrubsteppe habitats, based on the ground cover requirements of their prey.
Biological Research Needs: Understanding of the wintering ecology, dispersal, site fidelity (breeding and winter), and possible differences between subpopulations east and west of the Rocky Mountains is needed for conservation planning. Other research needs include basic biology, color polymorphism, nomadism, and relationship between populations of hawks and prey, especially cyclic species. The effects of management actions and strategies on Ferruginous hawks is also poorly known (Bechard and Schmutz 1995).
Global Protection: Few to very many (1 to >40) occurrences appropriately protected and managed
Comments: One protected at Kevin Rim by BLM as an ACEC (Area of Critical Environmental Concern). Eight Key Raptor Areas are managed by BLM in Montana (Centennial Valley, Lima Foothills, Madison river, Sweetwater Breaks, Kevin Rim, Rocky Mountain East Front, Rock Creek-Thoeny Area, and Lone Tree Management Area).
Needs: Protect extensive areas of suitable habitat throughout the breeding and wintering range; protect concentrated prey sources such as prairie dog towns.
The ferruginous hawk requires large tracts of relatively undisturbed
areas . 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
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 .
Maximum consideration should be afforded this species when range
development is planned . 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
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 . 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 .
Additionally, severe overgrazing could affect ferruginous hawk nest site
selection by causing a decline in the regeneration of willows .
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 .
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 . It is also
important to avoid range improvement activities in areas of high
ferruginous hawk foraging use [3,10].
Relevance to Humans and Ecosystems
Ferruginous Hawks may be a problem for farmers, as they will occasionally prey upon chickens.
Ferruginous Hawks help to keep the rodent population in check.
Stewardship Overview: Conversion of grasslands to intensive cultivation has reduced the amount of preferred habitat that is available and has been implicated in the population decline of the species in some areas (Schmutz 1984, Faanes and Lingle 1995). Agricultural development has restricted the species to areas of greater topographic relief or other areas unsuitable for agriculture (Stewart 1975). Keys to management are providing suitable nest sites, protecting active nest areas from disturbance, and improving habitat for prey. Isolated trees and stringers should be protected from livestock in nesting habitat. Prescribed burning may increase habitat suitability in shrub-dominated areas. Practices that increase exotic plant species number or dominance should be discouraged. Artificial nests have been used to increase number of nesting pairs in areas where suitable sites are scarce (Schmutz 1984).
it is threatened by cultivation of land,shooting and reducing its main food supplies e.g.prairie dogs.
The ferruginous hawk (ferruginous = from Latin ferrum – iron, ferrgin-, iron rust, iron-rust color – reddish-brown), Buteo regalis (Latin, royal hawk), is a large bird of prey and belongs to the broad-winged buteo hawks. An old colloquial name is ferrugineous rough-leg, due to its similarity to the closely related rough-legged hawk (B. lagopus).
This species is a large, broad-winged hawk of the open, arid grasslands, prairie and shrub steppe country; it is endemic to the interior parts of North America. It is used as a falconry bird in its native range.
This is the largest of the North American Buteos and is often mistaken for an eagle due to its size, proportions, and behavior. Among all the nearly thirty species of Buteo in the world, only the upland buzzard (B. hemilasius) of Asia averages larger in length and wingspan. The weight of the upland buzzard and ferruginous broadly overlaps and which of these two species is the heaviest in the genus is debatable. As with all birds of prey, the female ferruginous hawk is larger than the male, but there is some overlap between small females and large males in the range of measurements. Length in this species ranges from 51 to 69 cm (20 to 27 in) with an average of 58 cm (23 in), wingspan from 122 to 152 cm (48 to 60 in), with an average of about 139 cm (55 in), and weight from 977 to 2,100 g (2.154 to 4.630 lb). Weight varies in the species relatively restricted breeding range. In the southern reaches of the species breeding range, i.e. Arizona, New Mexico and Utah, males average 1,050 g (2.31 lb) and females average 1,231 g (2.714 lb). In the northern stretches of the breeding range, in southern Canada, Washington, Idaho and North Dakota, the hawks are heavier averaging 1,163 g (2.564 lb) in males and 1,776 g (3.915 lb) in females.
Adults have long broad wings and a broad gray, rusty, or white tail. The legs are feathered to the talons, like the rough-legged hawk. There are two color forms:
- Light morph birds are rusty brown on the upper parts and pale on the head, neck, and underparts with rust on the legs and some rust marking on the underwing. The upper wings are grey. The "ferruginous" name refers to the rusty color of the light-morph birds.
- Dark-morph birds are dark brown on both upperparts and underparts with light areas on the upper and lower wings.
There are no subspecies.
The voice is not well-described in literature. Alarm calls consist of kree – a or ke – ah and harsh kaah, kaah calls, the latter resembling some vocalizations of the herring gull. One description referred to the "wavering" alarm call and "breathy" notes, while other authors describe screams similar to those of the red-tailed hawk (B. jamaicensis).
The male and female have identical markings. The main difference is size, with the female being somewhat larger. Perched birds have a white breast and body with dark legs. The back and wings are a brownish rust color. The head is white with a dark streak extending behind the eye. The wing tips almost reach the tip of the tail.
The underside is primarily light colored with the dark legs forming a "V" shape. The reddish upper-back color extends to the inner wing coverts or "shoulders." The primary remiges (pinions) are dark gray with conspicuous light "windows" in the inner primaries. Three prominent light areas on the upper surface stand out as two "windows" on the outer wings and a rufous rump mark, perhaps the most signature feature of a flying ferruginous hawk. The underwings are whitish overall with rufous markings, particularly in the patagial area. This gives a smudgy appearance to the wings, but less dark than in a red-tailed hawk. The ferruginous hawk is noticeably longer winged than a red-tailed hawk, although the wings appear slenderer than the latter species the total wing area of the ferruginous is considerably more. However, the Red-tail can be nearly as bulky and heavy. Dark "comma"-shaped markings are prominent at the wrists. The ferruginous hawk is one of the only two hawks that have feathers that cover their legs down to their toes, like the golden eagle. The other is the rough-legged buzzard (Buteo lagopus). The pale morph of the closely related but more slender rough-legged species is best distinguished by its darker coloration, with a broad black tail band and a dark band across the chest. The dark morph Rough-leg is more a slaty coloration than the more brownish dark morph ferruginous. Swainson's hawks and especially rough-legged buzzards can be nearly as long-winged but are less bulky and heavily built than the ferruginous. Among the normal standard measurements, the wing chord measures 415 to 477 mm (16.3 to 18.8 in), the tarsus measures 81 to 92 mm (3.2 to 3.6 in) and the tail measures 224 to 252 mm (8.8 to 9.9 in). Additionally, the grasp is 94 to 125 mm (3.7 to 4.9 in) and the third toe 29.5 to 45 mm (1.16 to 1.77 in), indicating that the ferruginous hawks has the largest and most robust feet of any of the world's Buteos. Compared to other Buteos, the ferruginous has a larger bill, at 37.6 to 49.5 mm (1.48 to 1.95 in), with a much wider gape when the bill is opened, at 42.7 to 57 mm (1.68 to 2.24 in).
In flight, these birds soar with their wings in a dihedral.
The preferred habitat for ferruginous hawks are the arid and semiarid grassland regions of North America. The countryside is open, level, or rolling prairies; foothills or middle elevation plateaus largely devoid of trees; and cultivated shelterbelts or riparian corridors. Rock outcrops, shallow canyons, and gullies may characterize some habitats. These hawks avoid high elevations, forest interiors, narrow canyons, and cliff areas.
During the breeding season, the preference is for grasslands, sagebrush, and other arid shrub country. Nesting occurs in the open areas or in trees including cottonwoods, willows, and swamp oaks along waterways. Cultivated fields and modified grasslands are avoided during the breeding period. The density of ferruginous hawks in grasslands declines in an inverse relationship to the degree of cultivation of the grasslands. However, high densities have been reported in areas where nearly 80% of the grassland was under cultivation.
The winter habitat is similar to that used during the summer. However, cultivated areas are not necessarily avoided, particularly when the crops are not plowed under after harvest. The standing stubble provides habitat for the small-mammal prey base needed by ferruginous and other hawks. One requisite of the habitat is perches such as poles, lone trees, knolls, rocky outcrops or large boulders. Ferruginous hawks nest in trees if they are available, including riparian strips, but the presence of water does not appear to be critical to them.
The ferruginous hawk maintains minimum distances from other nesting raptors but will nest closer than necessary, suggesting that the distance is not fixed. The "nearest neighbor" distance has varied from less than 1 mile (1.6 km) to as much as 4 miles (6.4 km) with an average of 2 miles (3.2 km). Nests facing different hunting territories are tolerated much closer than nests facing the same hunting territory. The minimum distance between nests is probably about one half mile on densely occupied areas. Nesting densities in several studies have varied from one pair per four to 2,450 square miles (10.4 to 6,346 square km). In Alberta, on one study site, there was a stable density of one pair per four square miles (10.4 square km), on average with little deviation from this mean. In Idaho, the average home range for four pairs of ferruginous hawk in the Snake River area was slightly over two square miles (5.2 square km).
The flight of the ferruginous hawk is active, with slow wing beats much like that of a small eagle. Soaring with the wings held in a strong dihedral has been noted, as well as gliding with the wings held flat, or in a modified dihedral. Hovering and low cruising over the ground are also used as hunting techniques. The wing beat has been described as "fluid" by some observers.
Conflicts over territories, food and nest-defense have been reported with several other large species of raptor, such as the great horned (Bubo virginianus) and short-eared owl (Asio flammeus), hen harrier (Circus cyaneus), red-tailed and Swainson's hawks (Buteo swainsonii), golden eagle (Aquila chrysaetos), accipiters (Accipiter), ravens (Corvus), and magpies (Pica). Among native raptorial birds, only larger eagles and similarly sized great horned owls can regularly outmatch this large and powerful hawk. While bald eagles (Haliaeetus leucocephalus) normally only harass ferruginous hawks to pirate food from them, the golden eagle can be a serious killer (in potential territorial or defensive conflicts) and predator of the ferruginous. Although they may be attracted to similar nesting habitat, in a local comparison in northwestern Texas, southwestern Oklahoma and northeastern Arizona, the typical prey taken by Swainson's hawks was quite different, being about half the weight of that of the ferruginous hawk and more focused on insects rather than mammals. However, in the Morley Nelson Snake River Birds of Prey National Conservation Area, the prey taken by red-tailed hawks and ferruginous hawks was almost exactly the same, both in terms of species and body size. The prey species hunted by golden eagles are often similar, but the ferruginous hawk is locally less of lagomorph specialist where it co-exists with eagles and takes typically smaller prey, such as pocket gophers, which are generally ignored by the eagles. It seems to be quite tolerant of conspecifics from adjacent territories.
Hunting and feeding
The ferruginous hawk primarily hunts small to medium-sized mammals but will also take birds, reptiles, and some insects. Mammals generally comprise 80–90% of the prey items or biomass in the diet with birds being the next most common mass component. The diet varies somewhat geographically, depending upon the distribution of prey species, but where the range of the ferruginous hawk overlaps, the black-tailed jackrabbit (Lepus californicus) is a major food species along with ground squirrels and pocket gophers. Depending upon the relative abundance of jackrabbits and ground squirrels, the latter could become the major food source. Mammalian prey can range in size from tiny pocket mice to the white-tailed jackrabbit (Lepus townsendii), weighing about twice as much as a ferruginous hawk, and avian prey can range in size from western meadowlarks (Sturnella neglecta) to the greater sage-grouse (Centrocercus urophasianus). Common prey items are:
These birds search for prey while flying over open country or from a perch. They may also wait in ambush outside the prey's burrow. Hunting may occur at any time of the day depending upon the activity patterns of the major prey species. A bimodal pattern of early morning and late afternoon hunting may be common. The hunting tactics can be grouped into seven basic strategies:
- Perch and Wait – perching is on any elevated natural or man-made site
- Ground Perching – the hawk will stand on the ground at a rodent burrow after initially locating it from the air. As the burrowing animal reaches the surface, the hawk rises into the air and pounces upon it even while it is still underneath the loose earth.
- Low-level Flight – birds will course over the landscape within a few yards of the ground and pursue in direct, low level chases, or they will hunt from 40 to 60 feet (12 to 18 m) above the ground.
- High-level Flight – birds will hunt while soaring, but the success rate is generally low.
- Hovering – using quickened wing beats, often in times of increased winds, the birds will search the ground and drop on the prey.
- Cooperative Hunting – mates have been known to assist each other.
- Piracy – the ferruginous hawk has been observed gathering around a hunter shooting prairie dogs, and to claim shot "dogs" by flying to them and mantling over them.
In its "strike, kill, and consume" type of predation, the prey is seized with the feet and a series of blows may be meted out, including driving the rear talon into the body to puncture vital organs. Biting with the beak may also take place. Before bringing prey to the nest, the adults will often eat the head. At the nest, birds are plucked and mammals torn into pieces before being fed to the young. Food caching has been noted, but not generally near the nest.
Reproduction and life history
Copulation occurs during and after nest building. The egg-laying period varies with latitude, weather, and possibly food supply. In the Canadian parts of the range, laying occurs from the latter part of April through late June, whereas farther south laying occurs from about March 20 through mid May. The earliest recorded clutch was in January in Utah and laying could occur as late as July 3 in Canada. Egg-laying occurs at two-day intervals with incubation starting when the first egg is laid. Incubation is shared by both sexes with each taking approximately the same number of shifts during the 32-day average incubation period. Replacement clutches following failure appears to be rare.
Courtship flights seem to be limited in the accepted sense. Both sexes engage in high, circling flight but literature details are sketchy. Soaring activities may primarily be variations on territorial defense flights as opposed to courtship per se. The "flutter-glide" flight consists of a series of shallow, rapid wing beats interspersed with brief glides and may serve to advertise the territory. The "sky-dance" is stimulated by an intruder and consists of slow flight with deep, labored wing beats with irregular yawing and pitching that may terminate in steep dives. In the "follow-soar" maneuver, the male ferruginous hawk will fly below an intruder and escort it out of the territory.
High perching occurs from prominent places around the nest, particularly early in the breeding cycle. Aggressive actions such as attacking, talon-grasping, and pursuit have been noted by some observers. Copulation begins before construction of the new nest, and increases in frequency until the start of egg laying. The passing of food may occur before the activity. The duration of copulation is from four to 18 seconds.
The ferruginous hawk is one of the most adaptable nesters of the raptors, and will use trees, ledges, rock or dirt outcrops, the ground, haystacks, nest platforms, power poles, and other man-made structures. Within some broad categories such as cliffs, the variety includes clay, dirt and rock substrates. Tree nests are typically in isolated trees or isolated clumps of trees in exposed locations. Authors differ as to whether ground nests are more successful than tree nests, but they are more susceptible to mammalian predation. Nest locations are reused frequently, but several nests may be built in an area. Typically, one or two alternate nests may exist but up to eight have been found on some territories.
The nests are made of ground debris such as sticks, branches, and cattails. Old nests will be refurbished, or nests of other species may be taken over and refurbished with sticks being added on top of the old nests. Odd items such as paper, rubbish, barbed wire, cornstalks, plastic and steel cable have been incorporated into nests. Bark from trees and shrubs will be used for lining along with grasses and cow dung. Bits and pieces of greenery are often added to the nest. Prior to the removal of the bison from this bird's range, nesting material often included bison bones, fur and dung. Both sexes are involved with building the nests and bringing materials, but the male seems to be more involved in retrieving materials while the female arranges them in the structure.
Clutch size varies from one to eight and is likely linked to food supply. The average clutch is three to four eggs, each 2.5 inches (6.4 cm) long and 2 inches (5.1 cm) wide. They are smooth, non-glossy and whitish in color, irregularly spotted or speckled and blotched with reddish-brown markings. There may be a concentration of darker pigments at the small end of the egg. Occasionally, the eggs are almost unmarked or have faint scribblings on them.
The nestling period varies from 38 to 50 days with brooding primarily by the female. Males fledge at 38 to 40 days and the females as late as 50 days after hatching, or 10 days later than their male siblings as they take longer to develop. Nestlings lie or sit for the first two weeks, stand at about three weeks and walk soon after. By 16 or 18 days, they are able to feed on their own. Wing flapping starts about day 23 and by day 33 the young are capable of vigorous flapping and "flap jumps." The nestlings are sensitive to high temperatures and seek shade however possible in the nest.
Initial movement out of the nest is felt to be a response to heat stress as the young quickly move towards shade. The initial flight for the males is taken at 38 to 40 days while the slower-developing females fly about 10 days later. Post-fledging dependency upon the parents may last for several weeks. During the first four weeks after fledging, the young patrol increasingly large areas around the nest as they learn to hunt. Young hawks have killed prey as early as four days after fledging.
The ferruginous hawk is single-brooded, and as in so many raptors, the number of young reared is tied closely to food supply. In areas where jackrabbit populations are the principal food source, the initial clutch sizes and the number of reared young vary closely with variations in the number of jackrabbits. Fifty percent loss of young has been reported in low jackrabbit years. Fledging rates of 2.7 to 3.6 young per nest have been reported during years of abundant food supply. The high potential clutch size allows for a quick response to increases in the prey base.
Ferruginous hawks have been known to live for 20 years in the wild, but most birds probably die within the first five years. The oldest banded birds were recovered at age 20. First-year mortality has been estimated at 66% and the adult mortality at 25%. The reasons for mortality include illegal shooting, loss of a satisfactory food supply, harassment, predation, and starvation of nestlings during times of low food supply. Ground nests are susceptible to predation by coyotes, and nestlings may be preyed upon by great horned owls and golden eagles.
Status and conservation
At times the ferruginous hawk has been considered threatened, endangered, or of concern on various threatened species lists but recent population increases in local areas, coupled with conservation initiatives, have created some optimism about the bird's future. It was formerly classified as a Near Threatened species by the IUCN, but new research has confirmed that the Ferrugineous hawk is common and widespread again. Consequently, it was downlisted to Least Concern status in 2008.
Declines are mostly due to loss of quality habitat. Although flexible in choosing a nest site and exhibiting a high reproductive potential, this bird's restriction to natural grasslands on the breeding grounds and specialized predation on mammals persecuted on rangelands may make conservation a continuous concern. Historically, the birds entirely disappeared from areas where agriculture displaced the natural flora and fauna; for example it was noted in 1916 that the species was "practically extinct" in San Mateo County, California. Studies have found that prairie dogs can be a main prey item for ferruginous hawks, linking them to the populations of prairie dog towns in the mid-west and southwestern United States, which have been declining in recent years. This bird may also be sensitive to the use of pesticides on farms; they are also frequently shot. Threats to the overall population include:
- cultivation of native prairie grassland and subsequent habitat loss
- tree invasion of northern grassland habitats
- reductions in food supply due to agricultural pest management programs
- shooting and human interference
The ferruginous hawk was on the National Audubon Society's "Blue List" of species felt to be declining. From 1971 to 1981 it retained its "blue" status, and from 1982 to 1986 it was listed as a species of "Special Concern." The United States Fish and Wildlife Service placed it in a category of "undetermined" in 1973, and various states have placed it in categories of "Threatened" or "Endangered." In Canada, the Committee on the Status of Endangered Wildlife in Canada considered this species "Threatened" in 1980.
Across the Canadian prairies, the range was diminishing up until 1980, and at that time, birds were felt to be occupying 48% of its original range. Numbers were generally felt to be diminishing and a total Canadian population was estimated at 500 to 1000 pairs. By 1987, population increases were being noted, and the Alberta population alone was estimated at 1,800 pairs. The upswing was likely due to a greater availability of food on the wintering grounds, making the birds more likely to breed when they returned to Canada. In the United States, there has been a history of concern for this species in many states with declines noted, but in 1988, one study suggested that the population in California and locally elsewhere may have increased significantly. The wintering population north of Mexico was estimated at 5,500 birds in 1986. In 1984, the population estimate for North America was between 3,000 and 4,000 pairs, and in 1987, it was 14,000 individuals.
Toxic chemicals have not been suggested as a significant threat to the ferruginous hawk. Management strategies must include the retention or reclamation of native grasslands for breeding as well as on the wintering grounds. Maintenance of high populations of prey species in wintering areas seems critical to the hawks' abilities to move onto the summer range in breeding condition. The integration of agricultural practices and policies into the management strategies is a crucial component of any overall scheme for conservation. The provision of nesting platforms has had positive effects and should be a part of local strategies. Public education and the elimination of persecution and human disturbance must be an important part of the overall conservation program.
Use in falconry
The ferruginous hawk is a well regarded falconry bird, though not recommended for beginners due to its size, power, and aggressive personality. For the experienced falconer it offers an opportunity to experience the nearest equivalent to hunting with the golden eagle with much lower risk of injury to the falconer by the hawk. Faster and stronger than the red-tailed hawk, the ferruginous hawk is effective in pursuit of larger hares and jackrabbits that are difficult prey for the red-tailed hawk and Harris's hawk, and with its agility is also more effective on large bird species than is the golden eagle.
- Part of this article incorporates text from the Bureau of Land Management, which is in the public domain.
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