Northern Harrier inhabits open grasslands, marshes, and sagebrush throughout North America where they are widespread but somewhat uncommon. They are often compared with owls, due to their similar facial disk, acute hearing, and ability to hunt and migrate in low light. However, Harriers typically migrate and hunt during daylight hours when they spend much of the time aloft, coursing over meadows and fields low to the ground in search of mice, voles and small birds, often tilting and turning revealing their characteristic "white rump." Harrier has very long legs adapted for capturing prey in tall grasses, or snatching a songbird out of the air that is flushed from the ground.
Northern breeders are migratory, wintering primarily in the Lower 48. Sometimes tens to hundreds of birds might gather over an area, and these birds roost communally, often with Short-eared Owls. Harriers perch (only briefly) on low posts or on the ground, and only rarely in trees. They are often called "chameleons" by hawk watchers because they can appear buteo-like in a soar and falcon-like in a glide. Harriers are fairly quiet, but give an emphatic "whew, whew, wee, wee, wee, wee, wee." They are vocal in small groups in winter, giving a high, whine when defending a patch or during aggression.
Perched, Harrier is slim bodied with long wings and long tail, head is small and slightly squarish.
In flight, silhouette is distinctive with long, narrow wings and long, slim tail. Wings do not bulge along trailing edge.
Body lacks "'chesty" appearance, and head is small.
Gliding, wings of taper sharply and project well past the base of the wings, appearing as a large falcon. However, they lack the broad head and chest, and tapered tail of Peregrine, Prairie, and Gyrfalcon.
Lightweight and able to gain lift easily at any time.
Tireless; flying for hours non-stop while hunting or migrating.
Wing beats are deep, fluid, and relaxed.
Hold their wings in a pronounced dihedral or modified dihedral, except when gliding on strong ridge updrafts when they hold slightly drooped wings.
Buoyant like Turkey Vulture teetering unstably from side to side, but differ in the maneuverability and quick bursts of speed and direction changes.
2 age classes: adult and juvenile. Adult males and females differ greatly in plumage, but juveniles similar to adult females. All Harriers have brilliant white uppertail coverts, commonly referred to as a "white rump."
Adult male is strikingly white below with black wing tips and a black trailing edge on the secondaries. Upperside is gray with faint, pale mottling on upperwing coverts, but appears uniform grayish. Birds in spring are paler above due to fading. Some males are washed rufous on the chest and leggings, and/or brownish on the head and upperwing coverts. All adult males have lemon-yellow eyes.
Adult female is streaked brown on buff below and dark brown above with tan to rufous mottling on upperwing coverts. Some have limited streaking on underbody, others show a rufous body. Eye color changes from dark brown to yellow over ~ 3 years.
Juvenile is very similar to adult female, but distinguished by their rich, rufous underparts, with faint dark streaking on the chest. The rufous below fades to whitish by spring, and look even more similar to adult female. Upperside is uniform brown. Upperwing coverts are mottled rufous fading to whitish by spring. Juvenile sexes are similar, but male has pale yellow eyes compared to dark brown on female.
Migration spans nearly full length of seasons. Harriers move south from August through December, and north from February with stragglers as late as June. In fall, the peak for juveniles occurs late September, the peak for adults is several weeks later. In spring, peak is from mid to late April.
Harrier is known to fly throughout the night at times.
From East to West --Kiptopeke State Park (VA), Hawk Mountain (PA), Derby Hill (NY), Niagara Peninsula (Ont.), Holiday Beach (Ont.), Lake Erie Metropark (MI), Whitefish Point (MI), Hawk Ridge (MN), Bountiful Peak (UT), The Goshute Mountains (NV), and Gunsight Mountain (AK), are all excellent sites to Harriers.
(Map from Cornell Lab of Ornithology's All About Birds. For dynamic distribution maps, visit the eBird website.)