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 light-morph birds with extensive brown and/or black patterning and increasingly dark-morph birds that ultimately are entirely black with limited but distinctive whitish areas. At the light end of the spectrum, adults 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. Immaturs show gray tail bands. 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 of adults 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 northern and central 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 morphs. 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 in the West (10%) and more common in the East (25%) 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 mainly from June through September although molting birds have been seen in November on their wintering grounds. 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 Light-morph - Perched
Type A
- a lighter head with varying but narrow, dark shaft streaking. These types are only found in about 15 percent of western birds and none are found in eastern birds. Males therefore tend to exhibit less contrast between the head and back whereas females exhibit more tendency for contrast, particularly in the east. Belly markings are important.
Type B
- head not lighter than upper body colors with wide, dark shaft streaking. Belly markings are important.
HEAD
- varies from nearly unmarked white through a gradient of increasing amounts of dark along the feather shafts
- a dark eye line is evident
- the throat also shows an increasing amount of dark streaking
- the beak is black and the cere orange-yellow to orange
- the eye is dark brown
- two broad head patterns have been recognized:
BODY
- the breast is white with streaking of variable width and ranging from light brown through dark brown. The breast often appears as a dark bib at some distance.
- the belly may be clear white or with varying degrees of dark barring or blotchiness
- the lower abdomen, sides and undertail coverts are white through increasing degrees of dark barring or streaking
- the back varies from gray-brown with white or tawny mottling
WINGS
- the coverts are dark overall and tend to have wedge-shaped terminal marks
- the secondaries have a gray-brown with some white tip markings
- the primaries are dark fuscous-black and the wing tips reach the tail tip or beyond
TAIL
- the general underside pattern ranges from white for the basal one half or two-thirds with a dark terminal area
- a series of blackish bands cross the underside, progressing from a wider one near the tip through narrower ones towards the base
- a narrow area at the very tip of the tail is white
- some variations show a dark, diffuse band near the tip and no other banding or at least partial banding along the outer tail feathers
- on the upper surface, the tail is distinctly patterned in the lighter birds with a whitish basal area and a broad dark terminal band that has brown or cinnamon zones within it.
LEGS
- the flanks and thighs range from whitish, heavily barred with dark brown
- the legs are feathered completely to the feet
- the feet are yellow and the talons are black
Adult Female Light-morph - Perched
Type A
- a lighter head with varying but narrow, dark shaft streaking. About 60 percent of eastern females and 27 percent of western females have this type of head that is generally lighter than the back. Color and intensity of belly band is important.
Type B
- head not lighter than upper body colors with wide, dark shaft streaking. Color and intensity of belly band is important.
HEAD
- varies from nearly unmarked white through a gradient of increasing amounts of dark along the feather shafts
- a dark eye line is evident in lighter birds
- the throat shows dark streaking
- the beak is black and the cere orange-yellow to orange
- the iris is dark brown
- two broad head patterns have been recognized
BODY
- the breast is creamy white with streaking of variable width and ranging from light brown through dark brown. The breast often appears as a dark bib at some distance
- the belly is seldom, if ever, clear white and always with varying degrees of dark blotchiness
- the lower abdomen, sides and undertail coverts are white through increasing degrees of dark barring
- the belly usually appears to have a band that is darker than the rest of the underparts and this tendency towards darker bellies is greater in females; it may be a solid or split band. There is often a creamy, "u-shaped" area between the breast and the belly.
- the back varies from gray-brown with white or tawny mottling. Females tend to be more brown than the gray-brown males
WINGS
- the coverts are dark overall and tend to have longitudinal shaft marks
- the secondaries have gray-brown with some white tip markings
- the primaries are dark fuscous-black and the wing tips reach the tail tip
TAIL
- the general underside pattern ranges from white for the basal one half or two-thirds with a dark terminal area
- the series of blackish bands cross the underside found in males are absent such that the dark terminal band is more of a brownish gradient from the light area into the dark
- this "field" of brown may or may not have a darker brown band within it; up to three dark bands found in adult females.
- a narrow area at the very tip of the tail is white
- on the upper surface, the tail is distinctly patterned with a whitish basal area and a broad dark terminal band that has brown or cinnamon zones within it.
LEGS
- the flanks and thighs range from whitish, heavily barred with dark brown
- the legs are feathered completely to the feet
- the feet are yellow and the talons are black
Immature Light-morph - Perched
Note that males and females look the same in the first-year plumage.
HEAD
- light, creamy base with variable brown streaking
- dark line behind the eye
- the head is more frequently lighter than the back than it is the same color. Type A heads are more common.
- the beak is black and the cere is greenish to greenish yellow
- the eye is light gray to light brownish gray; appears pale
BODY
- the breast is creamy with variable mounts of dark streaking
- the dark breast streaking is usually wide as opposed to narrow along the feather shafts and the feather margins are reddish brown
- the belly has a continuous, solid dark band which appears as a paler brown than in most adult females.
- the back is brown with colors more blended than in adults so that the mottling is less distinct
WINGS
- the coverts are dark overall
- the secondaries are gray-brown with some white tip markings
- the primaries are dark fuscous-black and the wing tips reach the tail tip
TAIL
- the underparts are white near the base with a dark brown to dusky band toward the tip, more like female tails
- the upper tail varies from being white near the base with a wide, dark terminal area
LEGS
- the leg feathers are clear, creamy and lightly to not spotted or barred
- the feet are greenish yellow to yellow and the talons are black
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 but these birds have numerous narrow dark tail bands and pale upper primary coverts. 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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