Circus cyaneus
northern harrier;hen harrier
(Also: northern harrier)

Northern harriers are found throughout the northern hemisphere. In the Americas they breed throughout North America from Alaska and Canadian provinces south of tundra regions south as far as Baja California, New Mexico, Texas, Kansas, and North Carolina. They are only rarely seen breeding in parts of the Atlantic coastal states, such as Vermont, Rhode Island, and Maine and are similarly rare in the arid and mountainous western interior, including most of California, Oregon, and Washington. Their winter range is from southern Canada to the Caribbean and Central America. (Macwhirter and Bildstein, 1996)

In the Palearctic, northern harriers breed throughout Eurasia, from Portugal in the west, to Lapland and Siberia in the north, and east through China. They winter in northern African and tropical Asia. (Macwhirter and Bildstein, 1996)

Northern harriers are found mainly in open habitats such as fields, savannas, meadows, marshes, upland prairies, and desert steppe. They also occur in agricultural areas and riparian zones. Densest populations are found in large expanses of undisturbed, open habitats with dense, low vegetation. In eastern North America northern harriers are found most frequently in wetland habitats. In western North America they are most abundant in upland habitats such as desert steppe. Northern harriers avoid forested and mountainous areas. (Eastman, 1999; Macwhirter and Bildstein, 1996; Wheeler and Clark, 1987)

Northern harriers have several characteristics which distinguish them from other birds. Specialized feathers around their face in the shape of a disk focus sound into their ears. Their wings form a dihedral when in gliding flight, and they have a distinctive white rump patch which is obvious during flight. (Wheeler and Clark, 1987)

Adult harriers have yellow eyes. Adult males are gray on their dorsal side. Ventrally, they are white, except for spots on their chest, and black wingtips. Adult females are a brown color, except for underneath their wings, where there are white stripes. Immature males and females resemble the adult female, but they have a darker shade of brown covering the dorsal side and a brownish rusty color underneath. Immature harriers have brown eyes. (Wheeler and Clark, 1987)

The length of adult males varies between 41 and 45 cm (16 to 18 in). The length of adult females varies between 45 and 50 cm (18 to 20 in). Typically the wingspan of adult males varies between 97 and 109 cm (38 to 43 in). The wingspan of adult females varies between 111 and 122 cm (44 to 48 in). The weight of adult males is approximately 290 to 390 grams(1/2 to 1 lb). The average weight of adult females is approximately 390 to 600 grams(1 to 1.3lbs). (Wheeler and Clark 1995,Weidensaul 1996,Ryser 1985,Wheeler and Clark 1987) (Wheeler and Clark, 1987)

There is very little information known concerning the lifespan of northern harriers. The longest lifespan reported is 16 years and 5 months. The average lifespan, however, is 16.6 months. The oldest reported breeding female was 8 years old.

Besides flying, northern harriers walk and hop. They use this method of locomotion while retrieving prey, collecting nesting materials, and retrieving nestlings that have strayed from the nest. (Macwhirter and Bildstein, 1996)

Harriers typically fly slow and low to the ground, gliding often, and sometimes seeming to hover. They occasionally soar. Males fly faster and are more agile in flight than either females or juveniles and have been seen overtaking prairie falcons. (Macwhirter and Bildstein, 1996)

Northern harriers may nest alone or in loose assemblages. Territorial behavior is minimal especially during the breeding season, except at the nest site where both males and females will defend their territory against conspecific intruders. In winter, however, females aggressively exclude males from prime feeding territories. Despite this strong territoriality on the part of females, individuals of both sexes roost on the ground communally during the non-breeding season. During migration, northern harriers, like other raptors, prefer not to fly over open water. (Macwhirter and Bildstein, 1996)

Northern harriers are active during the day and spend much of their time hunting.

Home Range

During breeding season both sexes tend to be territorial around the nests, but otherwise, home ranges tend to overlap. Monogamous male territories tend to be approximately 260 ha (2.6 km square) in size, ranging from 170 (1.7 km square) to 15,000 (150 km square) ha. (Macwhirter and Bildstein, 1996)

Northern harriers are especially vocal around the nest. Sounds of courtship are reflected by rapid kek, quik, or ek notes in series. Calls of distress are urgent and high pitched, also in rapid succession. This call is more nasal-sounding in males than in females. (Macwhirter and Bildstein, 1996)

There also exists a "food call", which is observed most frequently during breeding season. Females issue a piercing eeyah, eeyah scream, which may be repeated for several minutes. This is responded to by a barely audible purrduk chuckle by the male, which solicits the female from the nest. (Macwhirter and Bildstein, 1996)

Young harriers emit a "begging call" when they hear their parents or in response to seeing their parents fly overhead. This sound is often referred to as a pain call, and it is a series of chit notes. This sound only becomes more emphatic with increasing age. (Macwhirter and Bildstein, 1996)

Northern harriers, like most raptors, have a keen sense of vision. Northern harriers are unusual in that their owl-like facial ruff enhances their sense of hearing, which they use extensively in finding prey. (Macwhirter and Bildstein, 1996)

The diet is variable, depending on dominant prey types in the area. In areas with large populations of small mammals, they make up 95% of the diet. In northern grasslands, the diet may be almost exclusively Microtus voles. Northern harriers also eat other small vertebrates, including snakes, frogs, passerine birds, and small waterfowl. When hunting for food, harriers glide at a slow pace close to the ground until prey is found. Harriers then dive quickly to capture it. They may also hide in vegetation, waiting to pounce on prey. They sometimes store extra prey to eat later. (Dechant et al., 1998; Eastman, 1999; Macwhirter and Bildstein, 1996; Wheeler and Clark, 1987)

Northern harriers have many predators, including raccoons, skunks, American crows, common ravens, coyotes, feral dogs, red foxes, and great horned owls. American crows and common ravens prey on eggs, while other raptors, especially great horned owls, target nestlings. (Burton and Burton, 1989; Chinery, 1992; Eastman, 1999; Macwhirter and Bildstein, 1996; Ryser, 1985)

Northern harriers with young generally respond aggressively to predators. Defense ranges from aggressive distress calls to striking the intruder with closed talons. Males and females contribute equally to defense. (Macwhirter and Bildstein, 1996)

Northern harriers often compete with short eared owls for the same food source. Food shortages can occur because both hunt the same prey. Northern harriers have a tendency to steal prey away from short eared owls by harassing them until the owl drops its prey. Short eared owls have been known to hunt both at night and during the day, while northern harriers hunt only during the day. (Burton and Burton, 1989; Chinery, 1992; Eastman, 1999; Ryser, 1985)

Predation by northern harriers can have significant effects on populations of field mice and other rodents. (Macwhirter and Bildstein, 1996)

As prey, northern harriers provide food for some terrestrial predators, such as coyotes Canis latrans, striped skunks Mephitis mephitis, raccoons Procyon lotor, and red foxes Vulpes vulpes.

There are no negative affects of northern harriers on humans. (Chinery, 1992; Macwhirter and Bildstein, 1996)

Northern harriers help protect crops by reducing populations of field mice and other rodents. Unlike some other hawk species, they do not attack poultry. (Eastman, 1999; Macwhirter and Bildstein, 1996)

No conservation measures have been enacted specifically for this species, however, conservation measures for waterfowl and habitat management for game birds has increased local numbers of nesting northern harriers. The species is abundant enough to be rated "Least Concern" by the IUCN. It it protected under the Migratory Bird Treaty, and is listed in Appendix II of CITES. (Macwhirter and Bildstein, 1996)