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.
Animal Foods: birds; mammals; amphibians; reptiles
Foraging Behavior: stores or caches food
Primary Diet: carnivore (Eats terrestrial vertebrates)
Predation by northern harriers can have significant effects on populations of field mice and other rodents.
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.
Northern harriers help protect crops by reducing populations of field mice and other rodents. Unlike some other hawk species, they do not attack poultry.
Positive Impacts: controls pest population
There are no negative affects of northern harriers on humans.
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.
US Migratory Bird Act: protected
US Federal List: no special status
CITES: appendix ii
IUCN Red List of Threatened Species: least concern
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.
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.
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.
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.
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
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.
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.
Biogeographic Regions: nearctic (Native ); palearctic (Native ); oriental (Native )
Other Geographic Terms: holarctic
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.
Habitat Regions: temperate ; tropical ; terrestrial
Terrestrial Biomes: savanna or grassland ; chaparral
Wetlands: marsh
Other Habitat Features: agricultural ; riparian
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.
Range lifespan
Status: wild: 16.19 (high) years.
Average lifespan
Status: wild: 16.6 months.
Average lifespan
Status: wild: 197 months.
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.
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.
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)
Range mass: 290 to 600 g.
Range length: 41 to 50 cm.
Range wingspan: 340 to 384 mm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: female larger; sexes colored or patterned differently
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.
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.
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.
Known Predators:
Adult males show interesting behaviors during mating season. During mating season the male courts the female by flying high in the air and then dives down twirling and spinning. Males are sometimes polygynous and have 1 to 3 mates. During incubation the male provides food for the female, but he doesn't approach the nest. When he is near the nest he will call out, and as she comes to him he drops the food to her. During the breeding season northern harriers become very territorial and will attack other hawks, birds, or humans that approach their nesting areas.
Most males are monogamous, although some males are polygynous, having been known to pair with up to five mates in a season. Females are monogamous. This is due, not only to the female-biased sex ratio, but also to the abundance of food during the spring.
Mating System: monogamous ; polygynous
Harriers often nest in loose colonies of 15 to 20 individuals. The nest, built mostly by the female, is made out of sticks and padded on the inside with grass. The nest is built on the ground, often on raised mounds of dirt or clumps of vegetation.
Eggs are laid from mid-May to early June. They are white with a blue tint, and occasionally have brown spots. The eggs are approximately 47 x 36mm. Three to five eggs are laid, and incubation is only by the female.
The eggs hatch in approximately 31 to 32 days. Male harriers will contribute to the feeding of their offspring during the time they are in the nest and will watch over the nest for a maximum of 5 minutes when the female is away.
Breeding interval: Northern harriers breed once per season.
Breeding season: Primary females breed from April through July, while secondary females breed from May through September.
Range eggs per season: 3 to 5.
Average eggs per season: 4.4.
Range time to hatching: 28 to 36 days.
Range fledging age: 30 to 35 days.
Average age at sexual or reproductive maturity (female): 2 years.
Average age at sexual or reproductive maturity (male): 3 years.
Key Reproductive Features: iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
Average eggs per season: 5.
Average age at sexual or reproductive maturity (male)
Sex: male: 365 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 365 days.
Female investment in her offspring begins with the provisioning of yolk to her eggs. After laying, the female will spread her wings to shelter her young from rain and extreme sun. Her mate will provide food for her for about two weeks after the eggs hatch, then departs. Food is transferred to the female via the male by aerial-pass, and then the female feeds her young. When young reach fledgling stage and are able to fly sufficiently well, food transfer is made to them by their mother, also via aerial-pass.
Parental Investment: altricial ; pre-fertilization (Provisioning); pre-hatching/birth (Provisioning: Male, Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)
Intermediate in appearance between the slim bird hawks (genus Accipiter) and thick-set buzzards (genus Buteo), the Northern Harrier is most easily identified by its size (17 ½ - 24 inches), long wings, long squared-off tail, and conspicuous white rump patch. Male Northern Harriers are light gray above and pale below, while females are solid brown above and streaked brown and tan below. Like most species of raptors, females are larger than males. The Northern Harrier is found widely across Eurasia (where it is known as the Hen Harrier) and North America. In the New World, this species breeds across Canada, Alaska, and the northern tier of the United States. In winter, Northern Harriers may be found from the southern Great Lakes and Pacific Northwest south to Mexico, Central America, and the West Indies. In the Old World, this species breeds across northern Europe and Asia south to Portugal and northern China, wintering as far south as North Africa and South Asia. The Northern Harrier inhabits a variety of open habitats, including grassland, marshes, and agricultural fields. This species avoids built-up areas and forests. The diet of the Northern Harrier consists primarily of small mammals and songbirds. Due to this species’ preference for open habitat, Northern Harriers may be most easily observed flying low over the tops of tall grasses in search of prey. Less frequently, Northern Harriers may be seen soaring high over open areas, displaying their characteristic long tail and wings. This species is primarily active during the day.
Intermediate in appearance between the slim bird hawks (genusAccipiter) and thick-set buzzards (genusButeo), the Northern Harrier is most easily identified by its size (17 ½ - 24 inches), long wings, long squared-off tail, and conspicuous white rump patch. Male Northern Harriers are light gray above and pale below, while females are solid brown above and streaked brown and tan below. Like most species of raptors, females are larger than males. The Northern Harrier is found widely across Eurasia (where it is known as the Hen Harrier) and North America. In the New World, this species breeds across Canada, Alaska, and the northern tier of the United States. In winter, Northern Harriers may be found from the southern Great Lakes and Pacific Northwest south to Mexico, Central America, and the West Indies. In the Old World, this species breeds across northern Europe and Asia south to Portugal and northern China, wintering as far south as North Africa and South Asia. The Northern Harrier inhabits a variety of open habitats, including grassland, marshes, and agricultural fields. This species avoids built-up areas and forests. The diet of the Northern Harrier consists primarily of small mammals and songbirds. Due to this species’ preference for open habitat, Northern Harriers may be most easily observed flying low over the tops of tall grasses in search of prey. Less frequently, Northern Harriers may be seen soaring high over open areas, displaying their characteristic long tail and wings. This species is primarily active during the day.
The hen harrier (Circus cyaneus) is a bird of prey. It breeds in Eurasia. The term "hen harrier" refers to its former habit of preying on free-ranging fowl.[2]
It migrates to more southerly areas in winter. Eurasian birds move to southern Europe and southern temperate Asia. In the mildest regions, such as France and Great Britain, hen harriers may be present all year, but the higher ground is largely deserted in winter.
The northern harrier was formerly considered to be a subspecies of the hen harrier.
In 1758 the English naturalist George Edwards included an illustration and a description of the hen harrier in the first volume of his Gleanings of Natural History. He used the English name "The blue hawk". Edwards based his hand-coloured etching on a bird that had been shot near London.[3] When in 1766 the Swedish naturalist Carl Linnaeus updated his Systema Naturae for the twelfth edition, he placed the hen harrier with the falcons and eagles in the genus Falco. Linnaeus included a brief description, coined the binomial name Falco cyaneus and cited Edwards' work.[4] The hen harrier is now placed in the genus Circus that was introduced by the French naturalist Bernard Germain de Lacépède in 1799.[5][6] The genus name Circus is derived from the Ancient Greek kirkos, referring to a bird of prey named for its circling flight (kirkos, "circle"). The specific epithet cyaneus is from Latin and means "dark blue".[7] The species is monotypic: no subspecies are recognised.[6]
The hen harrier was formerly considered to be conspecific with the northern harrier.[6][8][9]
The hen harrier is 41–52 cm (16–20 in)[10] long with a 97–122 cm (38–48 in) wingspan.[11][12] It resembles other harriers in having distinct male and female plumages. The sexes also differ in weight, with males weighing 290 to 400 g (10 to 14 oz), with an average of 350 g (12 oz), and females weighing 390 to 750 g (14 to 26 oz), with an average of 530 g (19 oz).[10][12] Among standard measurements, the wing chord is 32.8 to 40.6 cm (12.9 to 16.0 in), the tail is 19.3 to 25.8 cm (7.6 to 10.2 in) and the tarsus is 7.1 to 8.9 cm (2.8 to 3.5 in).[12] It is relatively long winged and long tailed.[12]
The male is mainly grey above and white below except for the upper breast, which is grey like the upperparts, and the rump, which is white; the wings are grey with black wingtips. The female is brown above with white upper tail coverts, hence females, and the similar juveniles, are often called "ringtails". Their underparts are buff streaked with brown.[10] Immatures look like females but with less distinct barring, dark brown secondaries dark brown and less-streaked belly.[13]
The female gives a whistled piih-eh when receiving food from the male, and her alarm call is chit-it-it-it-it-et-it. The male calls chek-chek-chek, with a more bouncing chuk-uk-uk-uk during his display flight.[11]
This medium-sized raptor breeds on moorland, bogs, prairies, farmland coastal prairies, marshes, grasslands, swamps and other assorted open areas. A male will maintain a territory averaging 2.6 km2 (1.0 sq mi), though male territories have ranged from 1.7 to 150 km2 (0.66 to 57.92 sq mi).
These, are the one of the few raptorial birds known to practice polygyny – one male mates with several females. Up to five females have been known to mate with one male in a season. A supplementary feeding experiment on the Orkney islands showed that rates of polygyny were influenced by food levels; males provided with extra food had more breeding females than 'control' males that received no extra food.[14]
The nest is built on the ground or on a mound of dirt or vegetation. Nests are made of sticks and are lined inside with grass and leaves. Four to eight (exceptionally 2 to 10) whitish eggs are laid. The eggs measure approximately 47 mm × 36 mm (1.9 in × 1.4 in). The eggs are incubated mostly by the female for 31 to 32 days. When incubating eggs, the female sits on the nest while the male hunts and brings food to her and the chicks. The male will help feed chicks after they hatch, but does not usually watch them for a greater period of time than around 5 minutes.[15] The male usually passes off food to the female, which she then feeds to the young, although later the female will capture food and simply drop into the nest for her nestlings to eat. The chicks fledge at around 36 days old, though breeding maturity is not reached until 2 years in females and 3 years in males.
In winter, the hen harrier is a bird of open country, and will then roost communally, often with merlins and marsh harriers. There is now an accepted record of transatlantic vagrancy by the northern harrier, with a juvenile being recorded in Scilly, Great Britain from October 1982 to June 1983.[16]
This is a typical harrier, which hunts on long wings held in a shallow V in its low flight during which the bird closely hugs the contours of the land below it. Northern or hen harriers hunt primarily small mammals, as do most harriers. Up to 95% of the diet comprises small mammals. However, birds are hunted with some regularity as well, especially by males. Preferred avian prey include passerines of open country (i.e. sparrows, larks, pipits), small shorebirds and the young of waterfowl and galliforms. Supplementing the diet occasionally are amphibians (especially frogs), reptiles and insects (especially orthopterans).[12] The species has been observed to hunt bats if these are available.[17] Larger prey, such as rabbits and adult ducks are taken sometimes and harriers have been known to subdue these by drowning them in water.[12] Harriers hunt by surprising prey while flying low to the ground in open areas, as they drift low over fields and moors.[10] The harriers circle an area several times listening and looking for prey. Harriers use hearing regularly to find prey, as they have exceptionally good hearing for diurnal raptors, this being the function of their owl-like facial disc.[12] This harrier tends to be a very vocal bird while it glides over its hunting ground.
Little information is available on longevity in hen harriers. The longest-lived known bird is 16 years and 5 months. However, adults rarely live more than 8 years. Early mortality mainly results from predation. Predators of eggs and nestlings include raccoons, skunks, badgers, foxes, crows and ravens, dogs and owls. Both parents attack potential predators with alarm calls and striking with talons. Short-eared owls are natural competitors of this species that favor the same prey and habitat, as well as having a similarly broad distribution. Occasionally, both harriers and short-eared owls will harass each other until the victim drops its prey and it can be stolen, a practice known as kleptoparasitism. Most commonly, the harriers are the aggressors pirating prey from owls.[18]
This species has a large range. There is evidence of a population decline, but the species is not believed to be approaching the thresholds for the population decline criterion of the IUCN Red List (i.e., declining more than 30% in ten years or three generations). It is therefore classified as "least concern".[1] In the United Kingdom, however, hen harrier populations are in a critical condition, due to habitat loss and illegal killing on grouse moors.[19] In 2012 only 617 pairs remained, representing a fall of 20% from 2004.
In some parts of Europe people believed that seeing a harrier perched on a house was a sign that three people would die. Unlike many raptors, hen harriers have historically been seen favorably by farmers because they eat predators of quail eggs and mice that damage crops. Harriers are sometimes called "good hawks" because they pose no threat to poultry as some hawks do.
The hen harrier is a bird of open habitats such as heather moorland and extensive agriculture. However, much of its range, particularly in Ireland and parts of western Britain, has been (and continues to be) afforested, predominantly with non-native conifers such as Sitka spruce (Picea sitchensis) from North America.[20][21] Hen harriers nest and forage in commercial forestry when it is young, before the canopy closes (typically at between 9–12 and years old), but do not make much use of thicket and subsequent growth stages,[22][23] which typically comprise between 2⁄3 and 3⁄4 of the commercial growth cycle. Where forests replace habitats that were used by hen harriers they will therefore tend to reduce overall habitat availability.[24] However, where afforestation takes place in areas that were previously underutilised by hen harriers, it may increase the value of such areas to this species in the long-term.[25][26] Areas dominated by forestry may remain suitable to hen harriers provided that a mosaic of age classes is maintained within the forest, such that areas of young, pre-thicket forest are always available.
The hen harrier (Circus cyaneus) is a bird of prey. It breeds in Eurasia. The term "hen harrier" refers to its former habit of preying on free-ranging fowl.
It migrates to more southerly areas in winter. Eurasian birds move to southern Europe and southern temperate Asia. In the mildest regions, such as France and Great Britain, hen harriers may be present all year, but the higher ground is largely deserted in winter.
The northern harrier was formerly considered to be a subspecies of the hen harrier.
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