Learn All About Circus Cyaneus, the Hen Harrier

The Pallid Harrier, is a bird with a head very similar to that of owls due to the type of disc on its face, but this has no relation to owls, they are territorial birds with physical appearances to hawks. In the following article we will know more about the Circus Cyaneus, we will discover what is its diet, which are the predators and much more.

The Circus Cyaneus

The Hen Harrier, scientifically called Circus Cyaneus, is a bird of prey. The genus name Circus is derived from the ancient Greek kirkos, meaning “circle”, which refers to a bird of prey named for its circular flight. The specific Cyaneus is Latin, which has a meaning of “dark blue”.

While many taxonomic authorities tend to divide the Hen Harrier ( Circus Cyaneus ) and the Hen Harrier into distinct species, others consider them to be conspecifics. This species breeds in northern Eurasia. The term “hen harrier” refers to its former habit of preying on poultry. This species usually migrates to more southerly areas in the winter. Eurasian birds move into southern Europe and southern temperate Asia, in regions that are milder, such as France and Great Britain.

Description

The Pallid Harrier ( Circus Cyaneus ) is about 41 to 52 cm long with a wingspan that is 97 to 122 cm. It is similar to other Hen Harriers in having different plumage types for both males and females. The sexes also tend to differ in weight, with males weighing from 290 to 400 grams, with an average weight of 350 grams, and in the case of females usually weighing 390 to 750 grams, with an average weight of 530 grams.

Among the standard measurements, the wing chord is 32.8 to 40.6 cm, the tail is 19.3 to 25.8 cm and the tarsus is 7.1 to 8.9 cm. It is relatively long.

The male is mainly gray above and white below except for the upper breast, which is gray like the upperparts, and the rump, which is white; the wings are gray with black wing tips. The female is brown on the upperparts with white uppertail coverts, thus the females, and the young birds are very similar, often called “ringtails”. Their underparts are beige striped with brown.

In the regions of Eurasia, the adult male is sometimes called the “Gray Ghost” because of its striking plumage and spectral aura. The female gives a kind of whistled piih – eh when receiving food from the male, and her alarm call is like a kind of chit – it – it – it – it – it – et – it. The male tends to call with a chek – chek – chek – chek, and also with a chuk – uk – uk – uk which is more bouncy during his display flight.

Behavior

This medium-sized bird of prey tends to breed in moorlands, marshes, grasslands, coastal farmland meadows, marshes, prairies, marshes, swamps and other open areas. A male will maintain a territory averaging 2.6 km², although male territories have ranged from 1.7 to 150 km².

These, are one of the few raptors that are known to practice polygyny which is one male pair with several females. There have been up to 5 females known to mate with 1 male in a season. A supplementary feeding experiment on the Orkney Islands even showed that polygyny rates were influenced by food levels; males that were provided with extra food had more breeding females than the other ‘control’ males that did not receive extra food.

The nest is built on the ground or on a mound of earth or vegetation. The nests are also made of sticks and are covered with different kinds of grasses and leaves. They lay from 4 to 8, however, exceptionally, there have been cases where the female lays 2 to 10 eggs that are whitish in color. Eggs usually measure approximately 4.7 cm × 3.6 cm. The eggs are incubated mainly or specifically by the female for about 31 to 32 days.

When incubating the eggs, the female sits on the nest while the male is the one who hunts and brings food to her and the chicks. The male will help her feed the chicks once they hatch, but usually does not watch them for a period of time longer than about 5 minutes. The male usually passes the food to the female, and subsequently she feeds it to the young, although later the female will capture the food and simply drop it into the nest for her chicks to eat.

Chicks tend to fledge around 36 days of age, although reproductive maturity is not reached until 2 years in females and 3 years in males. In the winter seasons, Pallid Harriers ( Circus Cyaneus ) are open-field birds, and then roost in commons, often with merlins and marsh harriers. There is now an accepted record of transatlantic vagrancy by Northern Harriers, with a juvenile recorded at Scilly, Great Britain from October 1982 to June 1983.

Hunting Behavior

This is a typical harrier, usually hunting on long wings held in a shallow V in its low flight during which the bird closely hugs the contours of the ground beneath it. Hen Harriers ( Circus Cyaneus ) hunt primarily small mammals, as do most harriers. Up to 95 % of its diet consists of small mammals.

However, the birds are also hunted with some regularity, especially by males. Preferred avian bird prey includes open-field passerines, i.e., sparrows, larks, pipits, small shorebirds, and the young of waterfowl and galliformes. Complementing the diet of this species from time to time are amphibians, especially frogs, reptiles and insects, especially Orthoptera.

It has been observed that the species tends to hunt bats if they are available. On certain occasions prey that are larger, such as rabbits and adult ducks, are captured and the harriers have been known to subdue them by drowning them in water. Hen Harriers ( Circus Cyaneus ) hunt amazing prey while flying low to the ground in open areas, as they slowly drift over fields and moors.

Pallid Harriers ( Circus Cyaneus ) circle an area several times listening and searching for prey. Harris Eagles use hearing regularly to find prey, as they possess exceptionally good hearing for diurnal raptors, which is the function of their owl-like facial disc. This harrier tends to be a very vocal bird as it glides over its large hunting territory.

Mortality and Competition

Little information is available on the long lifespan of harriers. The longest known bird is 16 years and 5 months. However, adults are rarely living longer than 8 years. Early mortality is mainly due to predation. Predators of eggs and chicks include the:

Both parents tend to attack potential predators with alarm calls and by striking with their claws.Short-eared Owls are natural competitors of this species that favor the same prey and habitat, and have an equally wide distribution.

Occasionally, both Hen Harriers ( Circus Cyaneus ) and short-eared owls will harass each other until the victim releases its prey and the prey can be stolen, a practice that is well known as kleptoparasitism. Most commonly, eaglets are the aggressors that kidnap prey from owls.

Status

This species has a wide range. There is some evidence of a population decline, but the species is not believed to approach the thresholds for the IUCN Red List population decline criteria, i.e., decline of more than 30% in 10 years or 3 generations. They are therefore classified as “Least Concern”.

In the UK, however, harrier populations are in a critical condition, due to extensive habitat loss and illegal killing on grouse moors. In 2012 there were only about 617 pairs left, representing a 20 % drop since 2004.

Relationship with Humans

In some parts of Europe people believed that seeing a harrier perched on a part of the house was a sign that 3 people would die. Unlike many other birds of prey, historically farmers have looked favorably on Hen Harriers ( Circus Cyaneus ) because they eat predators of Quail eggs and crop-damaging mice. Pallid Harriers ( Circus Cyaneus ) are sometimes called “good hawks” because they do not pose a threat to poultry, as some hawks do.

Silvicutor

The Hen Harrier ( Circus Cyaneus ) is a bird of open habitats, such as heather moorland and extensive agriculture. However, much of its range, particularly in the regions of Ireland and parts of western Britain, has been and continues to be forested, predominantly with non-native conifers such as Sitka spruce ( Picea sitchensis ) from North America.

Hen Harriers ( Circus Cyaneus ) tend to nest and forage in commercial forestry when young, before the canopy closes which is typically between 9 to 12 y years, but do not make much use of the shrub and subsequent growth stages, which typically comprise between 2

They are very rarely seen breeding in parts of the Atlantic coastal states, such as Vermont, Rhode Island and Maine, and are equally rare in the arid and mountainous western interior, including much of California, Oregon and Washington. Their winter range is from southern Canada to the Caribbean and Central America.

In the Palearctic, Northern Hen Harriers ( Circus Cyaneus ) breed throughout Eurasia, from Portugal in the west, to Lapland and Siberia in the north, and also east through China. This bird species tends to winter in northern Africa and tropical Asia.

Habitat

Northern Hen Harriers ( Circus Cyaneus ) are found mainly in open habitats such as in the:

They also occur in agricultural areas and riparian zones. Populations that are denser are found in large tracts of open, undisturbed habitats with low and dense vegetation. In eastern North America, Northern Hen Harriers are found at a higher frequency in wetland habitats. In western North America they are more abundant in upland habitats such as desert steppe. Northern harriers avoid forested areas as well as mountainous areas.

Home Range

During the breeding season, both sexes always tend to be very territorial around nests, but otherwise home ranges tend to overlap. Male territories that are monogamous tend to be about 2.6 km² in size, ranging from 1.7 km² to 150 km².

Reproduction

Adult males exhibit certain interesting behaviors during the mating season. During the mating season, the male usually courts the female by flying high in the air and then dives in a spinning and twirling motion. Males are sometimes polygynous and have 1 to 3 mates.

During incubation periods, the male is the one who provides food for the female, but does not approach the nest. When he is near the nest, he will scream, and when she approaches him, he throws food at her. During the breeding season, Hen Harriers become very territorial birds 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 mate with up to 5 females in one 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.

Longevity

Very little information is known about the lifespan of Hen Harriers ( Circus Cyaneus ). The longest reported lifespan is that of a bird of about 16 years and 5 months. The average life expectancy, however, is 16 years and 6 months. The oldest reported breeding female was 8 years old.

Communication

Northern Harriers ( Circus Cyaneus ) are especially vocal birds around the nest. Courtship sounds are reflected in rapid notes such as kek, quik or ek in series. Distress or distress calls are urgent and high-pitched, also in rapid succession. This call is more nasal in males than in females.

There is also a kind of “food call”, which is more frequently observed during the breeding season. Females usually emit a high-pitched eeyah, eeyah scream, which may be repeated for several minutes. This is answered by a purring laugh that is barely audible emitted by the male, who solicits the female from the nest.

Young harriers also emit a “begging call” when they hear their parents or in response to seeing their parents fly overhead. This type of sound is very often called a pain call, and is a series of chit notes. This sound only becomes more emphatic with increasing age of the young.

Northern Hen Harriers ( Circus Cyaneus ), like most raptors, possess a keen sense of vision. Northern harriers are unusual in that their owl-like facial ruff enhances their sense of hearing, which is used extensively to find prey.

Feeding Habits

The diet of this bird tends to be variable, depending on the types of prey that are dominant in the area. In areas with large numbers of small mammal populations, they represent 95% of the diet. In northern grassland areas, the diet may be almost exclusively of Microtus campani. Pallid Harriers ( Circus Cyaneus ) also eat other small vertebrates, such as the:

When this species of bird is searching for food, the Pallid Harrier glides at a slow pace close to the ground until it finds prey. They may also hide in vegetation, waiting to attack their prey. Sometimes they store their extra prey to eat later.

Predation

Hen Harriers ( Circus Cyaneus ) have many predators, including raccoons, skunks, American crows, common ravens, coyotes, feral dogs, red foxes, and great horned owls. American crows and common ravens feed on their eggs, while other raptors, especially great horned owls, target nestlings.

Hen Harriers with young usually respond aggressively to predators. Defense ranges from aggressive distress calls to striking the intruder with clenched talons. Males and females contribute equally to the defense.

Hen Harriers very often compete with short-eared owls for the same food source. Food shortages may occur because they both hunt the same prey. Northern harriers tend to steal prey away from short-eared owls by harassing them until the owl drops its prey. Short-eared owls are known to hunt both at night and during the day, while Northern Harriers hunt only during the day.

Known Predators

American Crow ( Corvus brachyrhynchos )

Common Ravens ( Corvus corax )

Coyotes ( Canis latrans )

Great Horned Owls ( Bubo virginianus )

Stray Dogs ( Canis lupus familiaris )

Striped Skunks ( Mephitis mephitis )

Red Foxes ( Vulpes vulpes vulpes )

Raccoons ( Procyon lotor )

Ecosystem Roles

Pallid Harrier ( Circus Cyaneus ) predation can have very significant effects on populations of voles and other rodents that are considered pest species for humans.

As prey, Hen Harriers provide food for some terrestrial predators, such as coyotes Canis latrans, striped skunks mephitis mephitis, raccoons Procyon Procyon, and foxes Vulpes vulpes.

Economic Importance to Humans in a Positive Way

Hen Harriers ( Circus Cyaneus ) help protect crops within their territorial range by reducing populations of voles and other rodents. Unlike the other hawk species, they do not attack poultry.

Economic Importance to Humans in a Negative Way

There are no negative effects of Hen Harriers ( Circus Cyaneus ) on humans. Because their food chain does not include poultry or other farmer’s animals, only field mice, which are considered a pest to humans.

Conservation Status

Certain conservation measures have not been enacted specifically for this species, however, conservation measures announced for waterfowl and habitat management for gamebirds have increased the local number of nesting Hen Harriers ( Circus Cyaneus ). The species is abundant enough to be classified as of “Least Concern” by the IUCN organization. This species is protected by the Migratory Bird Treaty and is listed in Appendix II of CITES.

Interesting Species Facts

  • Pallid Harriers ( Circus Cyaneus ) are the most owl-like hawks however they are not related to owls. They rely on both hearing and their sense of sight to capture prey. The disk-shaped face looks and functions similarly to an owl, with stiff facial feathers that help direct sound to the ears.

 

  • Young males have pale yellow-greenish yellow eyes, while females have dark brown eyes. The eye color of both sexes gradually changes to lemon yellow as they reach adulthood.
  • Male Hen Harriers ( Circus Cyaneus ) can have up to 5 females at a time, although most have only 1 or 2. The male provides most of the food for his mates and their offspring, while the females incubate the eggs and raise the chicks.
  • Hen Harriers ( Circus Cyaneus ) hunt mostly small mammals and small birds, but are capable of capturing larger prey such as rabbits and sometimes ducks. Sometimes they subdue larger animals by drowning them.
  • The oldest Pallid Harrier ( Circus Cyaneus ) on record was a female, and was at least 15 years, 4 months old when she was captured and subsequently released in 2001 by a banding bird in Quebec.