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ferruginous hawk
Buteo regalis

STATUS

California Species of Special Concern

LIFE HISTORY

The ferruginous hawk is an open country species. It is a large broad-winged hawk with a large head and chest. Generally, there is an overlap in body measurements of males and females and they are similar in coloration; however, females often exhibit more rufous on the legs and belly.

Similar to other buteos, the ferruginous hawk has at least two color morphs, light and dark, with variations in between. In all morphs of the ferruginous hawk, the eyes of the nestlings are gray, turning yellow with maturity, and the cere (base of the bill) and feet are yellow. The adult light morph has a white or gray tail and mostly white underparts. A few spots of rufous or gray are found on the belly and on the undersides of the wings, especially on the leading edges, and deep rufous on the legs extending down to the toes. The amount of rufous on the undersides of the wings and across the belly can vary.

When seen from below while the hawk is in flight, the typical light morph exhibits a characteristic rufous V formed by the rufous legs and feet help up under the rump. With the wings extended there is a white window near the wrist on the upper surface of the wing. The back and shoulders are rufous with the remaining upperparts grayish black. The head is a pale gray or dark brown with eye stripes, and a white patch on each cheek.

Immature birds of the light morph lack much of the rufous markings on the undersides of the wings and have whitish, not rufous, feathers on their legs. The upper surface of the tail has a white base with large black spots and a grayish terminal band. Fledglings have rufous chests that fade by fall.

The adult and fledglings of the dark morph of the ferruginous hawk have the same coloration. Most of the body is dark with a light-colored tail and light areas on the upper and lower surfaces of the wings.

Ferruginous hawks are found in open habitats, such as grasslands, shrubsteppes, sagebrush, deserts, saltbush-greasewood shrublands, and outer edges of pinyon-pine and other forests. Generally, they avoid high elevations, narrow canyons, and interior regions of forests. Trees, utility poles and towers, fence posts, rocky outcrops, cliffs, and the ground are perching substrates used by ferruginous hawks.

In the winter in California, these hawks prefer grassland and arid areas with an abundance of prey species, such as pocket gophers, black-tailed hares (jackrabbits), and cottontails. They also will winter near cultivated fields that have an abundance of pocket gophers. In such areas, the hawks will sometimes roost in groups of up to 24 individuals.

Ferruginous hawks depend on only a few prey species. In the western states, their diet includes cottontails, black-tailed hares, ground squirrels, and pocket gophers. Some bird species are captured during the breeding season and fed to the nestlings.

Furruginous hawks hunt throughout the day; in some areas they are crepuscular (active at dusk and dawn) because the prey species are crepuscular. Most frequently used methods of hunting include: perch and pounce, hunting from a perch with short flights to capture prey; and ground ambush, hunting from the ground near a ground squirrel burrow or fresh pocket gopher mound, striking the prey as it emerges. Occasionally, these hawks hunt while in flight or while hovering, the latter usually used in strong winds. In addition to communally roosting in the winter, the ferruginous hawk is known to hunt communally.

The breeding season begins with nest building or refurbishing in March or April. Nests consisting of old twigs, stems, branches of sagebrush, and litter from the ground, including dried manure, and often measure greater than about 1 meter (3.28 ft) in diameter and height. Prior to the 1900's in North Dakota, nests were constructed of old bison bones. Nests are located at various heights, from ground level to greater than 19.8 m (65 ft) above the ground. This species prefers elevated nest sites, such as boulders, low cliffs, haystacks, utility structures, artificial nesting structures, and trees. In areas where elevated sites are not available, they will nest on level ground.

Depending on prey abundance, the size of the clutch can range from one to eight eggs, but the average is two to four eggs being laid at 2-day intervals. Incubation is estimated to last between 32 and 33 days with both parents performing the duty. The young leave the nest (fledge) between 38 and 50 days old; males may leave up to 10 days earlier than females. At 52 days old, fledglings can kill prey, but they usually remain dependent on their parents for several weeks after fledging. Young begin to leave the nesting area between 28 and 40 days after fledging. Typically, ferruginous hawks are two years old when they first breed and may live up to 20 years of age.

The ferruginous hawk population is thought to be declining throughout its range. Agricultural development is considered to be the most serious threat to this species. Other threats include the effects of grazing, poisoning and controlling of small mammals, mining, and fire in the nesting habitats. Although it is not as significant a problem in the breeding range, shooting may still be a problem in this species' wintering range, including California.

Distribution

Ferruginous hawks inhabit the open habitats in western North America. Thier breeding range extends from southern Canada between the Great Plains and the Rocky Mountains, south to northern Arizona and New Mexico. Their wintering range extends from northern California south to Baja California, east through southern Nevada, southwestern and northeastern Utah to central Kansas, south to southeastern Texas and throughout the southwestern states, and into Mexico. In the winter months, they are most common in the southwestern United States.

In the winter, ferruginous hawks can be found throughout California, with the exception of the extreme northeastern and northwestern regions. However, they are most common in the southern region of the state. The hawks begin to migrate into California in August or September and return to their breeding habitat in late February or early March.

CLASSIFICATION

Order FALCOIFORMES, Family ACCIPITRIDAE, Genus Buteo, Species regalis

SUBSPECIES

None.

RECENT SYNONYMS

None.

OTHER COMMON NAMES

Ferruginous rough leg

REFERENCES

Bechard, M. J., and J. K. Schmutz. 1995 . Ferruginous Hawk (Buteo regalis). In The Birds of North America, No. 172 (A. Poole and F. Gill, eds). The Academy of Natural Sciences, Philadelphia, and The America Ornithologists' Union, Washington, DC; Wheeler, B. K., and W. S. Clark. 1995. A photographic guide to North American raptors. Academic Press, San Diego, CA, 198 pp; Johnsgard, P. A. 1990. Hawk, eagles, and falcons of North America: biology and natural history. Smithsonian Institution Press, Washington, DC, 403 pp; State of California, Dept. Fish and Game. 1990. California's Wildlife, Vol. II: Birds (D.C. Zeiner, W.F. Laudenslayer, Jr., K. Mayer and M. White, eds.). The Resources Agency, Sacramento, 407 pp; Clark, W. S., and B.K. Wheeler. 1987. A field guide to hawks: North America. The Peterson field guide series, Houghton Mifflin Co., Boston, MA, 198 pp.

SIZE

Length:
55.9-68.6 cm (22-27 inches)
Wingspan:
134.6-152.4 cm (53-60 inches)
Weight:
0.96-2.07 kg (34-73 ounces)

IDENTIFICATION

The ferruginous hawk looks similar to morphs of the red-tailed hawk (B. jamaicensis) and the rough-legged hawk (B. lagopus). The light morph of the red-tailed hawk has a dark marking on the leading edges of the underwings, versus the rufous marks of the ferruginous hawk, and the adult ferruginous hawk lacks bands on it tail. The light morph of the rough-legged hawk typically has a solid dark belly band, dark square wrist patches, and heavily marked underparts. Other dark morphs of Buteo species lack the white wrist commas (on the underwing), and except for the rough-legged immatures and some individual red-tailed hawks, usually have different tail patterns.

AUTHOR OF PROFILE

N. L. Brown

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