By Jim Graves
We have been watching a family of raptors swoop and soar around a neighborhood wetland throughout the summer. These relatively small hawks are Northern Harriers. Harrier means hunter and the harrier jet, which can take off and land vertically, was named for it. This avian hunter was formerly known as the Marsh Hawk because it prefers hunting in open areas such as grasslands and wetlands. The scientific name, which has not changed, is Circus cyaneus; Circus, which means circular, most likely refers to the beautiful wide surveillance flights made close to the ground. They fly with slender wings held up elegantly in a slight “V” and when they spot their prey, such as small mammals (especially voles), birds, reptiles, or insects, they will plunge suddenly out of sight.
Northern Harriers are widely distributed around the northern hemisphere. According to Montana Partners in Flight, Eastern Montana supports some of the highest densities of this species in the nation; it is estimated that as much as 70% of the state could be suitable habitat for the species. They are threatened today, like so many other avian species, by loss of habitat (wetlands and native grasslands) and pesticides.
These hawks are easily identified by their very distinct white rump patch at the base of the tail. The adult male and female look quite different, however: the male is white below with a light gray back and hood and obvious black wingtips; the female is brown above and speckled white and brown below. The female is also quite a bit larger than the male. Body lengths of adults range from 17-24 inches and the wingspan can be 4.5 feet. The adults weigh usually between 12 and 20 ounces. The Peregrine Fund reports that, unlike most hawks, harriers can use their sense of hearing to help locate prey. Harriers have an owl-like facial disk to help with directional hearing and soft feathers for a quieter flight. The eyes of an adult male are yellow. The female is born with brown eyes which turn yellow at about three years of age. Juveniles resemble adult females, but have gray eyes and have buff underparts.
Montana Natural Heritage Program reports that Harriers arrive here to breed in March and April. Northern harriers usually return to the same area to nest. Courtship occurs through early May and the acrobatic flights of the agile males consisting of a series of U-shaped maneuvers are elaborate. Their courtship call is a series of “kek” or “ke” notes. Males may have two mates, but usually only one female is able to successfully produce young because the male typically favors one mate and her nestlings with food. Northern Harriers nest on the ground or over water on platforms of emergent vegetation. The majority of nests are located in undisturbed wetlands or grasslands which have thick vegetation such as brome, wheatgrass, and western snowberry. The female lays 3 – 6 eggs depending on the abundance of food. The eggs are pale blue when first laid but then turn to dull white; some may have brown spots. The female begins incubating with the second to fourth egg and the eggs will begin hatching in about 32 days. The male helps care for the young by hunting for food and bringing it to the female in mid-air. A female, after receiving prey in flight from the male, will not return directly to the nest but will make several false landings to confuse predators. Female harriers will aggressively protect their nests; we have watched one chase away a red tail hawk half again her size. It has also been reported that humans who approach too close to a nest are often dived at by these vigilant mothers. The call given by harriers when they are threatened has been described as a rapid nasal chattering, ke-ke-ke, The begging call is a piercing, descending scream. It can be startling. The young that hatch in June can fly at 30-35 days and are on the wing in abundance in early August. Harriers mature in 2 – 3 years, but may be able to breed their first year if prey is abundant.
Some harriers may winter in Montana, though most head south beginning in September. They head for Mexico, Central America, northwestern South America and the West Indies. Becky Lomax in a 2004 Montana Outdoors article reported that raptors travel along the Rocky Mountain Front on their annual migratory paths. Many birds of prey fly near Rogers Pass, along the Continental Divide about halfway between Helena and Great Falls from September through mid-November. On an average day during the fall migration, over 40 raptors fly over Rogers Pass including Golden eagles, Sharp-shinned hawks, red-tailed hawks, rough-legged hawks, Cooper’s hawks, northern goshawks, kestrels, and of course, northern harriers. Blustery days are better for viewing than balmy ones because prey are often out on the good days and raptors are feeding rather than flying. Becky included these directions to the viewing area on Rogers Pass: “follow U.S. Highway 287 north from Wolf Creek. The next 21 miles run along the FWP survey route. At Bowman’s Corner, turn west onto Montana Highway 200 toward Rogers Pass. A few miles past the Stearns-Augusta road crossing, a marked pullout on the road’s north side denotes the Rocky Mountain Front Eagle Migration Area with an “Eagle Watch” sign. You can monitor migrating raptors with scopes and binoculars there and at any unmarked pullouts between there and Rogers Pass. In early fall you can watch from the Continental Divide Trail north or south from Rogers Pass. If you plan on walking off-road in the Rogers Pass area, don’t bother or disrupt researchers trapping and banding raptors. Walk quietly and move through the trees rather than out in the open, where raptors can spot you from afar.”
Researched and compiled by Linda deKort