The Ferruginous Hawk is a large, long-winged buteo of the open, arid grasslands and shrub steppe country of the interior parts of North America. It occurs in a light and dark color phase with the latter being much less common in general. It's hunting and flight behavior is suggestive of a Golden Eagle and it survives primarily on small to medium-sized mammals and less so on birds. 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. It is migratory in the northern parts of its range but can be found year round in the mid and southwest United States. At times it 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.
SIZE
This is the largest of the buteos and is often mistaken for an eagle due to its size, proportions and behavior. References are inconsistent in reporting the dimensions of this hawk, but all agree that the sexes overlap and the females average larger than the males. Reported length measurements range from 20 to 26 inches (51 to 66 centimeters) with an average of 23 inches (58 centimeters); wingspans from 48 to 60 inches (122 to 152 centimeters) with an average of 56 inches (142 centimeters); and weights from 2.2 to 4.5 pounds (998 to 2,041 grams). The average weight for females from some references was 2.8 pounds (1.270 grams), and for males it was 2.3 pounds (1.043 grams). References do not distinguish genders for some measurements.
MORPHS AND MOLTS
There are two basic color morphs recognized. The adult light-morph is light-headed with rich reddish-browns and blacks on the upper body surface, and a white underbody with reddish flanks and reddish markings on the underwing surface. The adult dark morph is dark-headed with dark upperparts and an all dark belly and underparts. The underparts of the wing are two-toned, with the dark axillars and coverts contrasting with the silvery white primaries and secondaries. There is some variability within the morphs and individuals will interbreed freely. Some populations may have more dark morphs than others. Overall, it appears that dark morphs range from three to 30 percent of a population. The average for North America has been suggested at 10 percent or less of the population being comprised of dark-morph birds.
The juvenile plumage is retained throughout the first winter and into the following spring / summer. By the second fall, the bird molts directly into full adult plumage. By the second spring, most birds should have full adult plumage. Subsequent molts of the adults occur between spring and fall and their appearance remains consistent.
SPECIFIC DESCRIPTION
Adult Light-morph - Flight
- outer primaries small and black and look as if they have been "dipped in ink"
- a large buteo with a reddish upper back and inner wing coverts or "shoulders"
- it appears very long-winged, often holding them up in a dihedral
- the primaries are dark gray with conspicuous light "windows" or "panels" in the innerprimaries
- the upper surface of the tail appears whitish towards the base and rump with varying degrees of rufous coloration towards the tip, and it appears unbanded
- three prominent light areas on the upper surface stand out as two "windows" on the outer wings and a rufous rump mark
- the underwings are whitish overall with rufous markings, particularly in the patagial area, perhaps giving a smudgy appearance but less dark than Red-tailed Hawk
- dark "comma" shaped markings are prominent at the wrists
- the general underparts appear starkly white with the rufous thigh feathering forming a dark "v" mark against the light undersides
Immature Light-morph - Flight
- general upperparts are similar to the adults
- outer primaries small with gray tips
- dark area on flanks
- large legs push spotted flank feathers together and form a conspicuous dark mark
- upper tail lacks the rufous wash and the white upper tail coverts has dark spotting along the lower perimeter
- the underwings are cleanly white with few markings, but the black wrist comma is evident; the white "leggings" do not contrast with the underbelly as in adults
- the tail below is whitish with a dusky band near the tip
- upper tail is white at basal one-quarter to one-third
- has whitish panels, or "windows", on upper primary surfaces like an adult
SIMILAR SPECIES
In size and behavior, the Ferruginous Hawk is the buteo which most closely resembles the Golden Eagle, but it is smaller and differs quite dramatically in plumage in both color phases. Depending upon viewing conditions and lighting, it could be mistaken for a number of other buteos if the observer was only looking at gross patterns and ignoring size or other combinations of features. Some features of the Ferruginous Hawk similar to the same features in other species are as follows:
dihedral wing posture,
- Swainson's Hawk, Rough-legged Hawk, and Turkey Vulture
dark body, dark underwing,
- all dark buteos
long, broad wings,
- Golden Eagle
hovering behavior,
- Osprey and Rough-legged Hawk
Some races of Red-tailed Hawk have similarities that could cause confusion. Differences occur in wing and tail patterns.
OTHER NAMES
The Ferruginous Hawk is also known as the "Ferruginous Rough-leg", "Ferruginous Rough-legged Hawk", "Chap Hawk", "Gopher Hawk", "Prairie Eagle", "Squirrel Hawk", and "Ferrugy."
ETYMOLOGY
The genus name Buteo is Latin for "buzzard", which is an early name for hawks and vultures. It is allied with the Greek "buzo" which means "to hoot". This has little relevance to the calls of any diurnal birds of prey. The specific name regalis is Latin for "regal" or "royal", but the name comes from the location in Mexico where this species was first found and described. Real del Monte is the locale, and "Real" is Spanish for "royal." Ferruginous refers to the rusty-red colors and stems from the Latin "ferrugo" or "rust." The word "hawk" has its origins from the Teutonic base "hab", which ultimately led to the Middle English derivative "hauk." Hab meant "to seize or hold."
