Spotted harrier (Circus assimilis)

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Spotted harrier in flight, ventral view
IUCN Red List species status – Least Concern LEAST
CONCERN

Top facts

  • The spotted harrier is named for its white-spotted plumage.
  • The spotted harrier typically hunts by flying low over open ground, using its acute hearing to locate prey.
  • Uniquely among harriers, the spotted harrier nests in trees rather than on the ground.
  • Unlike other harriers, in which the male mates with several females, the spotted harrier forms monogamous pairs.
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Spotted harrier fact file

Spotted harrier description

KingdomAnimalia
PhylumChordata
ClassAves
OrderFalconiformes
FamilyAccipitridae
GenusCircus (1)

The spotted harrier (Circus assimilis) is a relatively large bird of prey with a slim, lanky build, long, broad wings and a relatively long, wedge-tipped tail. It has a short, broad head and an owl-like ruff of feathers around the face (2) (3) (5) (6) (7).

Unusually for a harrier species, the male and female spotted harrier are similar in appearance, although the female is generally larger. Both sexes have blue-grey upperparts and chestnut underparts, which are covered in white spots (2) (3) (5) (6). The face and shoulders are also chestnut coloured and the head and face are streaked with grey (2) (3). The spotted harrier’s tail is marked with black bands, while its wings are tipped with black and have white spotting above and below (2) (3) (7).

Adult spotted harriers have yellow eyes and a yellow area of skin, known as the cere, at the base of the beak (2) (3). The legs are also yellow, and are relatively long and slender (2) (3) (5) (6) (7).

Juvenile spotted harriers are quite different in appearance to the adults, being largely dark brown above and pale buff to pale reddish-brown below. The feathers on the juvenile’s upperparts have buff to ginger edges, its head and face are reddish-brown, and its underparts are marked with fine dark streaks. The juvenile spotted harrier’s tail is barred, as in the adult, and its eyes are dark brown. In its second year of life the spotted harrier develops more adult-like plumage, but has browner, more mottled upperparts, brown streaks on the head and face, and heavily white-streaked underparts (2) (3).

Although generally silent, the spotted harrier may give a piercing, high-pitched ‘wik wik wik’ call during the breeding season, as well as a rapid, chattering ‘kikikikik(3) (4) (5).

Also known as
allied harrier, Jardine’s harrier, smoke hawk, spotted swamp hawk, spotted swamp-hawk.
Size
Length: 50 - 61 cm (2) (3)
Wingspan: 121 - 147 cm (2) (3)
Male weight: 412 - 537 g (2)
Female weight: 530 - 745 g (2)
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Spotted harrier biology

Like other harriers, the spotted harrier characteristically hunts by making low, quartering flights over the ground as it searches for prey (2) (5) (9). Its flies with its wings held in a ‘V’ shape, and has a buoyant flight with slow wing beats and long glides. This species also soars high in the air and sometimes hovers, and it often dangles one or both legs as it flies (2) (3).

The spotted harrier’s diet includes small mammals and ground-dwelling birds such as quails and pipits, as well as reptiles and large insects. It also occasionally eats carrion (2) (5) (6) (7) (9). The owl-like ruff of feathers on the spotted harrier’s face, together with asymmetrically placed ear openings, help it to detect sounds made by prey and accurately locate them, while its long legs help it to reach into long grass or reeds to capture its victim (3). Prey is usually taken on the ground, occasionally after a short chase (2) (9).

The spotted harrier is usually seen alone or in pairs. Unlike most harriers, in which the male mates with several females, the spotted harrier is monogamous (2) (3), and pairs defend large territories (2). This species is also unique among harriers in that it regularly nests in trees rather than on the ground (3) (9), possibly as an adaptation to avoid ground predators (3). The nest consists of a flimsy platform of sticks, lined with green leaves (2) (5) (6) (9).

Breeding in this species generally takes place between July and December, but the spotted harrier can breed at any time of year in arid parts of central Australia, depending on rainfall (2). The female spotted harrier lays a clutch of 2 to 4 eggs, which she incubates for 32 to 34 days (2) while the male hunts and brings her food (5). The young spotted harriers leave the nest at 36 to 43 days old, but remain dependent on the adults for at least 6 more weeks (2) (9).

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Spotted harrier range

The spotted harrier occurs across most of mainland Australia, except for densely forested areas, and its range also extends to Sulawesi and the Lesser Sunda Islands (2) (3) (8) (9). This species also occasionally occurs as a vagrant in Tasmania (2) (3).

In many areas the spotted harrier is nomadic, moving around in response to rainfall and food abundance (2) (5) (9). Populations in southern Australia tend to be migratory, generally moving northwards in winter (2) (9).

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Spotted harrier habitat

The spotted harrier inhabits open woodland, grassland and scrub, as well as cultivated areas (2) (3) (7) (9), at elevations of up to 1,500 metres (2). It is typically found in arid and semi-arid areas (5) (9). The spotted harrier also sometimes hunts over coastal grassland, heath and swamps (2) (3) (7), but usually avoids wetlands (2).

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Spotted harrier status

The spotted harrier is classified as Least Concern (LC) on the IUCN Red List (1) and is listed on Appendix II of CITES (4).

IUCN Red List species status – Least Concern

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Spotted harrier threats

The spotted harrier is a widespread bird and its overall population is believed to be stable (8). In some areas, such as Sulawesi, this species is likely to be benefitting from deforestation and the creation of more open habitats (2).

However, the spotted harrier is thought to be declining in some parts of Australia. Potential threats to this species include accidental poisoning from chemicals used to control rodents and rabbits, and reduced prey availability due to the spread of rabbit calicivirus disease. Rabbits are not native to Australia, but the spotted harrier may not be able to depend on native prey species, which are being affected by habitat clearance and degradation (7) (10) as well as the removal of ground cover due to overgrazing (11).

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Spotted harrier conservation

The spotted harrier is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), meaning that any international trade in this bird of prey should be carefully controlled (4).

No other specific conservation measures are currently known to be in place for the spotted harrier, but recommended actions include protecting its habitat from overgrazing and development, protecting its nesting habitat (7), and using appropriate grazing regimes that help to maintain populations of its prey (11).

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Find out more

Find out more about the spotted harrier and its conservation:

More information on conservation in Australia:

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Authentication

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

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Glossary

Carrion
The flesh of a dead animal.
Cere
In birds, an area of skin at the base of the upper mandible of the beak, surrounding the nostrils.
Incubate
To keep eggs warm so that development is possible.
Monogamous
Having only one mate during a breeding season, or throughout the breeding life of a pair.
Nomadic
A species which roams irregularly from place to place in search of food and water, without returning to a fixed location.
Territory
An area occupied and defended by an animal, a pair of animals or a colony.
Vagrant
An individual found outside the normal range of the species.
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References

  1. IUCN Red List (April, 2013)
    http://www.iucnredlist.org/
  2. Ferguson-Lees, J. and Christie, D.A. (2001) Raptors of the World. Helm Identification Guides, A&C Black Publishers, London.
  3. Debus, S. (2012) Birds of Prey of Australia: A Field Guide. Second Edition. CSIRO Publishing, Collingwood, Australia.
  4. CITES (April, 2013)
    http://www.cites.org/
  5. Birds in Backyards - Spotted harrier (April, 2013)
    http://www.birdsinbackyards.net/species/Circus-assimilis
  6. Moro, D. and MacAulay, I. (2010) A Guide to the Birds of Barrow Island. Chevron Australia, Perth. Available at:
    http://www.chevronaustralia.com/environment/protectingenvironment/nature-books.aspx
  7. NSW Government, Office of Environment & Heritage - Spotted harrier profile (April, 2013)
    http://www.environment.nsw.gov.au/threatenedspeciesapp/profile.aspx?id=20134
  8. BirdLife International - Spotted harrier (April, 2013)
    http://www.birdlife.org/datazone/speciesfactsheet.php?id=3405
  9. Global Raptor Information Network - Spotted harrier (April, 2013)
    http://www.globalraptors.org/grin/SpeciesResults.asp?specID=8205
  10. NSW Government, Office of Environment & Heritage - Spotted harrier Circus assimilis Jardine and Selby 1828 - vulnerable species listing (April, 2013)
    http://www.environment.nsw.gov.au/determinations/spottedharrierFD.htm
  11. Attwood, S.J., Park, S.E., Maron, M., Collard, S.J., Robinson, D., Reardon-Smith, K.M. and Cockfield, G. (2009) Declining birds in Australian agricultural landscapes may benefit from aspects of the European agri-environment model. Biological Conservation, 142: 1981-1991.
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Image credit

Spotted harrier in flight, ventral view  
Spotted harrier in flight, ventral view

© Hans & Judy Beste / www.ardea.com

Ardea wildlife pets environment
59 Tranquil Vale
London
SE3 0BS
United Kingdom
Tel: +44 (0) 208 318 1401
ardea@ardea.co.uk
http://www.ardea.com

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