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
Adult Male Light-morph - Flight
- a large, long-winged, long-tailed buteo that often hovers in flight and holds its wings in a dihedral
- the head may but tends not to contrast markedly from the back colors except for a small percentage of western birds
- the underwings are always two-toned with the coverts varying from moderately to heavily- streaked with dark markings
- the primaries are contrastingly lighter with dark tips
- dark carpal patches are usually prominent features; many males have very mottled carpal patches that do not contrast.
- tail with one or more dark bands
- dark edge trailing wings
- belly, flanks, and legs with spots or bars; sometimes belly is all-white to almost all-white on some birds
- the back is variably mottled dark or blackish with a contrasting white base to the tail or a dark tail with narrow white bands
Adult Female Light-morph - Flight
- a large, long-winged, long-tailed buteo that often hovers in flight and holds its wings in a dihedral
- the head may contrast markedly from the back colors more so in eastern than western birds
- the underwings are always two-toned with the coverts varying from moderately to heavily- streaked with dark markings
- the primaries are contrastingly lighter with dark tips
- dark edge to hind (trailing) part of wings
- all-dark carpal patches are prominent features; not mottled as in many males.
- there are four prominent dark areas on the underside set against a lighter background. These are the two carpal patches, a darker belly band (solid or split), and the dark terminal area of the tail. The terminal area usually lacks the multiple bands of the male and is more of diffuse brown area that may have a darker band within it.
- the back is variably mottled gray-brown with a contrasting white base to the tail
Immature Light-morph - Flight
- a large, long-winged, long-tailed buteo that often hovers in flight and holds its wings in a dihedral
- the head more frequently contrasts markedly from the back colors
- the underwings are less obviously two-toned in lighter birds as the coverts may be unmarked. The tips of the flight feathers are dark and the solid dark carpal patches are obvious.
- gray edge to hind (trailing) part of wings
- individuals may tend to look more white on the underside with a solid dark belly band - the uppertail is more cleanly white at the base contrasting with the gray terminal band, much as black band on adults
- the upper side is variably dark but the primaries always show whitish areas (panels) on the top side. They are absent in adults.
- the under tail surface has a large white area at the base and a dusky terminal band
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."
