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NORTHERN
HARRIER Circus cyaneus |
| The Northern harrier, also known
as the marsh hawk, is unique in many ways. It is North America's only harrier,
our sole representative of a widespread genus whose member species can be
found on every continent except Antarctica. Alone among North American diurnal
(active by day) raptors, the harrier has a facial disc, a
prominent ruff of feathers around the bird's face that gives it a distinctly
owlish look. Facial discs act as sound collectors, channeling sound waves
into ear openings, and they allow both owls and harriers to pinpoint a sound's
origin with uncanny accuracy. Like owls, harriers have unusually large ear
openings, and like many species of owls harriers hunt mostly by listening.
They can detect and catch prey that is completely hidden by vegetation at
a distance of up to 10 feet. Harriers are birds of open spaces, frequenting fresh and saltwater marshes, farmland, meadows wet and dry, tundra, prairie and grasslands. They prefer terrain with low vegetation, and they hunt these open spaces with a unique style. The species hunts by coursing, by zigzagging slowly across an open area, using its hearing abilities to detect prey in the vegetation. The harrier's distinctive flying style is a direct result of its distinctive build. This medium-sized hawk is slender and lightly built, with very long wings, legs and tail. Proportionately, in fact, the harrier's tail is the longest of any North American raptor's. The long, narrow wings combined with that long tail give the harrier a mothlike buoyancy that enables it to fly very slowly without stalling. This graceful hawk typically courses almost lazily 10 to 30 feet above the ground, deliberately quartering (crisscrossing back and forth) treeless terrain with a series of slow, deep and regular wingbeats, the downstroke of which end with a distinct snap that characterizes the harrier even at a considerable distance. The steady wingbeats are interspersed at intervals with short, sailing glides. Then another harrier characteristic can be seen. During the glide the wings are held stiffly above the body in a bold dihedral (V-shape). As the lightweight harrier wings slowly over the ground, it typically tips and tilts, moved by the air currents. Its slow pace enables it to drop down instantly onto its luckless prey as soon as the victim is detected. This cruise-listen-pounce is the harrier's standard hunting technique, and it is usually employed to pick up rodents such as voles and mice. But this hawk is a versatile and opportunistic hunter, and it can also take small birds in flight or snatch them from cover with its long legs like an accipiter (a group of forest hawks that hunt mostly birds). Like an American kestrel it can pounce on frogs, small snakes and insects from a hover (a flight style in which a bird turns into the wind and flaps its wings hard while keeping the head and body motionless). It can still-hunt (to hunt by sitting motionless and watching) like a red-tailed hawk, taking young rabbits and squirrels. It can finish off wounded waterfowl and eat carrion in the manner of a bald eagle. In fact, it could be said that whatever is seasonally available is the harrier's favorite prey. The harrier can also steal from other raptors. In Middleboro, Massachusetts, harriers gather every winter to hunt over the extensive grasslands produced when swampland was converted to fields. The harriers aren't the only raptors hunting there. Short-eared owls hunt over the same terrain, and the larger, more powerful harriers have come up with an effective, energy-saving method of obtaining prey. They wait for the hard-working owls to snatch up a mouse, vole or shrew, and then the harriers simply move in and rob the hapless owls of their catch. And how is it that an owl and a hawk are hunting at the same time? Many owls, among them the short-eared owl, are not so much nocturnal (active by night) as they are crepuscular (active at dawn and dusk). Harriers are also crepuscular, which is unusual among hawks. Although harriers will hunt throughout the day, their peak activity is usually in the early morning and early evening hours. Female harriers are considerably larger and bulkier than the males, averaging 18 ounces in weight, while their wingspan averages close to 4 feet. Males average 12 ounces in weight, with a wingspan that averages close to 3 1/2 feet. Because of this size difference, prey taken by males and females may be different. Males tend to prey more on birds, while the larger females tend to hunt more mammals. The two genders may hunt in different areas as well. Females are usually found in large fields and meadows, while the males are more apt to chose smaller fields, particularly those abandoned for use and broken up by brush. In color males and females continue the pattern of being different. In fact, the two genders could be taken for different species, their coloration is so distinctly different. Adult females are various shades of brown and buff above, with longitudinal brown streaks on the creamy or buffy underparts. Males are an eye-catching silver-gray above, with the secondary feathers (the inside flight feathers of the wing, located between the primary feathers at the end of the wing and the bird's body, and shorter than the primary feathers) and the 5 outer primary feathers (the outermost and longest of the flight feathers of the wing) tipped with black. Juveniles or immatures (young birds) resemble the adult females. All ages and genders show a harrier characteristic - a flashing white rump patch that shows very clearly when the harrier is seen in its classic coursing flight. The harrier's home life is unusual as well. Male harriers may have several mates at one time, and they are the only North American raptor to do this on a regular basis. The harrier's breeding range extends across the northern part of the U.S. and up into the conifer forests of Alaska and Canada. Males court the females with acrobatic courtship flights, climbing steeply upward and then dropping down in a series of loops. At the highest point in each of these loops the male is actually upside down. The females build stick and grass nests on the ground, siting the nest in marshland or meadows. Egg-laying usually begins in May, and 4 to 6 eggs are usual. Incubation takes 29 to 39 days. When the young are about two weeks old they may scatter into the surrounding vegetation while the female joins the male in the hunting duties. At 4 to 5 weeks the young are on the wing. Migration begins at the end of August and may extend to the end of November. As is the case with broad-winged hawks, juveniles are the first to leave, followed by the adult females and finally by the adult males. Spring migration is the exact opposite, with the adult males leaving the wintering grounds first. The wintering grounds may be southern New England, or the birds may go as far as South America. The Northern harrier is habitat-dependent, meaning it needs open areas, particularly wetlands, to survive. As development has taken over the species' habitat, and as farming techniques have changed, making farmland less hospitable, the harrier population has been going down. As a breeding bird, the harrier seems to be fairly secure in New Hampshire and Maine, but it no longer nests in Connecticut, and Massachusetts is thought to have no more than a few dozen nests, most of them on the islands off Cape Cod. The birds seen in Connecticut and Massachusetts in the winter are primarily migrants that will leave in the spring. |