The Rough-legged Hawk is a large buteo and has been called lanky and angular. It is boldly-patterned and shows great variation from whitish birds with extensive brown and/or black patterning through increasingly dark birds that ultimately are entirely black with limited but distinctive whitish areas. Birds vary continuously from the light extreme through to the darkest extreme. At the light end of the spectrum, flying birds viewed from below are essentially whitish with heavy dark streaking showing distinctive dark patches in the carpal areas of the wing, across the belly and across the terminal portion of the tail. The dark band on the tail along with a white area at the base is visible from below and on the dorsal surface of flying birds. The wing tips are also dark. The darkest birds on the other hand, look completely black over the head and entire body. The wings are whitish underneath except for the black coverts and primary feather tips. The banded white and dark tail shows prominently from beneath as in lighter birds. Flight patterns are distinctive and include hovering as a frequently-used hunting tactic. Few buteos within the wintering range of this hawk hover as much as the Rough-legged Hawk. The wings are often held in a pronounced dihedral.
This is a bird of the open tundra when breeding and open country when wintering. It is highly migratory and moves from its arctic summer quarters to southern Canada and the United States for the winter.
SIZE
The Rough-legged Hawk is a fairly large buteo with females averaging larger than males. The overall length range, including both sexes, is from 18.5 to 20.5 inches (47.0 to 52.1 centimeters). The wingspan varies from 47 to 52 inches (119.4 to 132.1 centimeters). Some average measurements for females are: wing chord - 16.4 inches (41.7 centimeters) and tail - 8.8 inches (22.4 centimeters). The same average measurements for males are: wing chord - 16.3 inches (41.4 centimeters) and tail - 8.8 inches (22.3 centimeters). The averages mask the fact that females tend to be the individuals showing the longest measurements in the range for each of the preceding body parts. The weight range is from 1.7 to 3.1 pounds (771 to 1,406 grams) but on average, males weigh about 1.8 pounds (816 grams) and females 2.2 pounds (998 grams).
MORPHS AND MOLT
There are three subspecies recognized in the world but effectively only one in North America. There are no true color phases but rather, an unbroken continuum of variation from light to dark birds. Light and dark birds interbreed. The sexes differ in pattern in the adult (basic) plumage but not in the juvenile stage. The basic differences in color patterns are due mainly to the deposition of the dark pigment melanin. The variation is so great that each individual bird has its own unique pattern, but certain common patterns are evident. Melanism is relatively uncommon but can occur and add confusion to an already variable species. There is no post-juvenal molt. Birds of the year retain the feathers they acquire in the nest until the following spring when they begin to molt into the adult type plumage. Following that, birds undergo a single annual molt that takes place during the breeding season from June through September. The primaries molt from the 4th outward and the innermost 3 molt in sequence with the secondaries. The tail feathers molt from the central pair outwards. Females tend to molt earlier than the males.
SPECIFIC DESCRIPTION
The following description applies to Buteo lagopus sancti-johannis, the subspecies common to all of North America except Alaska where a zone of hybridization occurs. It should be noted that the range of variation between light and dark phases is great and attempting to describe a typical extreme for each is difficult. There are sexual differences in the tail pattern, belly pattern, marginal coverts, relative lightness of head to back, and the pattern of the dorsal feathers. These differences are most noticeable in the tail and belly patterns.
Adult Male Dark-morph - Perched
- body all-dark-brown to all-black; legs feathered to toes
- white patch with dark center on back of head
- dark eye; white to light forehead and outer lores
- dark brown to black tail with three to four narrow whitish bands of equal size
Adult Female Dark-morph - Perched
- body all-dark-brown; legs feathered to toes
- white patch with dark center on back of head which is often lighter or paler than in the male
- dark eyes; white to light forehead and outer lores
- tail is dusky-brown to dark brown above, whitish to silvery below with wide dark band at tip
Immature Dark-morph - Perched
- body all-medium to dark-brown, sometimes reddish-brown in the darkest birds; legs feathered to toes
- white patch with dark center on back of head
- pale to light brown eye
- tail dark above and silvery-white below with several lighter cross bands that are not white; dusky, not well defined, band near tip of tail
SIMILAR SPECIES
Lighter colored birds could be mistaken for the light phase Red-tailed Hawk but the latter does not have large dark carpal marks and lacks the white tail base contrasting with a dark terminal band. This latter tail feature could lead to confusion with the Northern Harrier but it is a slimmer looking bird with a longer tail and lacks the other obvious field marks such as carpal patches, dark belly banding and flight styles. Frequently, inexperienced observers mistake the Rough-legged Hawk for an Osprey, particularly due to the hovering flight pattern and the contrasting black and white patterning and wrist markings of lighter birds. Immature dark morph Ferruginous Hawks resemble immature, dark Rough-legged Hawks but the Ferruginous Hawk is larger and has white patches in the carpal area that are lacking in the Rough-legged Hawk. Similarly, a dark immature Red-tailed Hawk may appear similar to some observers. Darker Rough-legged Hawks may also be confused with the Zone-tailed Hawk based on broad plumage traits and the dihedral wing posture in both.
OTHER NAMES
The Rough-legged Hawk is also known as the "Roughie", "Rough-leg", "Black Hawk" (dark phase), "Chap Hawk", "Chicken Hawk", "Mouse Hawk", "Screech Hawk", "Squalling Hawk", and "Squealing Hawk."
ETYMOLOGY
The genus 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" which has little relevance to the calls of any diurnal birds of prey.The species name Lagopus is Greek for "hare-footed" with reference to the leg feathering extending down to the foot. Rough-legged is also a reference to the leg feathering and "hawk" has its origins from the Teutonic base "hab" which ultimately led to the Middle English derivative "hauk." Hab meant "to seize or hold."
MYTHOLOGY
None is known for North America.
VOICE
A commonly heard alarm call is a descending, cat-like, "kee-eer" scream. It has been likened to the scream of the Red-tailed Hawk. Soft "mews" have been heard in captive birds along with high-pitched whistling notes. Various "cheep" notes are given by the male along with squeals and squawks from the female. Two-syllable clucking notes and downslurred whistling noises are also noted for this species. The female also has a clucklike "nar-nar" call. Descending, slurred whistles are also part of the repertoire.
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