Circus assimilis

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Spotted Harrier
Circus assimilis


Status: Lower risk

Population Trend: Stable.

Other Names: Allied Harrier, Jardine's Harrier, Smoke Hawk, Spotted Swamp Hawk.

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Distribution: Australasian/Indomalayan. AUSTRALIA, SULAWESI, SULA ISLANDS, and the LESSER SUNDAS (Timor and Sumba). more....

Subspecies: Monotypic. more....

Taxonomy:

Movements: Partial migrant (Bildstein 2006) and often nomadic. In southern Australia, these harriers are spring-summer breeding migrants, generally moving northward for the winter, but the extent, timing, and location of migratory movements vary with seasonal conditions and the availability of food (Baker-Gabb 1983, Debus 1998). Juveniles may disperse up to 1,600 km after the breeding season (Debus op cit.). In southern Australia, birds return to their mainly semi-arid breeding areas in late winter or early spring (Saunders and Ingram 1995), but the numbers returning vary markedly from year to year (Baker-Gabb 1983). In arid regions, they arrive to breed only after sufficient rain has fallen, which is about one year out of every two or three (Brooker et al. 1979, Klau 1983). There are no known discrete overwintering areas of special significance for the arid and semi-arid migrants (Baker-Gabb and Fitzherbert 1989). more....

Habitat and Habits: Inhabits open country, including ricefields, scrub, grassland, cultivated areas, and occasionally coastal fishponds. Most often seen quartering over open country on upswept wings, sweeping low with wings raised in a V, over grasslands, shrublands, and through open woodlands of arid and saemi-arid Australia (Olsen 1995). Sometimes perches on the ground, but also on fenceposts and dead trees. Found singly or in pairs (Coates and Bishop 1997).

Food and Feeding Behavior: Feeds on small mammals (young rabbits, rodents), birds (quails, larks, pipits), reptiles, large insects, and rarely carrion (Debus 1998, Coates and Bishop 1997). Olsen and Trost (2007) saw one swoop into a farmyard on the island of Sumba, Indonesia, probably in pursuit of poultry. It forages by low quartering or transect hunting, sometimes by hovering, and seizes prey by diving to the ground or by a short chase if prey is flushed (Debus op cit.).

Breeding: Pairs nest solitarily. Unique among harriers in regularly nesting in trees. both in Australia (Olsen 1995) and on Sulawesi (Coates and Bishop 1997). The nest is a platform of sticks lined with green leaves and placed 2-15 m above the ground in a living tree, rarely on the ground (Debus 1998). Clutch size is usually 3 eggs (2-4), the incubation period is 33 days, and the nesting period is 36-42 days (Debus op cit.). The period of dependence after fledging lasts at least six weeks. more....

Conservation: Generally uncommon, but widespread. Classified as Near Threatened in Victoria (Debus 2009), and its reporting rate has declined nationally in Australia by 25% and in New South Wales by 55% (Debus 2008). However, it is categorized globally as a species of "Least Concern" by BirdLife International (2008). more....

Important References:
Baker-Gabb, D.J. 1982. Comparative ecology and behaviour of Swamp
  Harriers, Circus approximans, Spotted Harriers, Circus assimilis, and other
  raptors in Australia and New Zealand. Ph.D. thesis, Monash University,
  Melbourne, Australia.
Debus, S.J.S. 1994. Spotted Harrier. Pp. 138-139 in del Hoyo, J., A.
  Elliott, and J. Sargatal (eds). Handbook of birds of the world. Vol. 2. New
  World vultures to guineafowl. Lynx Edicions, Barcelona, Spain.
Debus, S. 1998. The birds of prey of Australia: a field guide. Oxford
  University Press, Melbourne.
Debus, S. 2008. Diurnal raptors under threat. Bird Observer 856:5-8.
Ferguson-Lees, J., and D.A. Christie. 2001. Raptors of the world. Houghton
  Mifflin, Boston, MA.
Marchant, S., and P. Higgins (eds.). Handbook of Australian, New Zealand,
  and Antarctic birds. Vol. 2. Raptors to lapwings. Oxford University Press,
  Melbourne, Australia.
Olsen, P. 1995. Australian birds of prey. John Hopkins University Press,
  Baltimore, MD.
Simmons, R. 2000. Harriers of the world: their behaviour and ecology.
  Oxford University Press, Oxford, UK.
Wink, M., and H. Sauer-Gürth. 2004. Phylogenetic relationships in diurnal
  raptors based on nucleotide sequences of mitochondrial and nuclear marker
  genes. Pp. 483-498 in R.D. Chancellor and B.-U. Meyburg (eds.), Raptors
  worldwide. World Working Group on Birds of Prey, Berlin, and MME/BirdLife
  Hungary, Budapest.
more....

Researchers:
Scott, Don

Last modified: 5/26/2010

Recommended Citation: Global Raptor Information Network. 2018. Species account: Spotted Harrier Circus assimilis. Downloaded from http://www.globalraptors.org on 22 Apr. 2018