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Swamp Harrier
Circus approximans

Status: Lower risk

Population Trend: Stable.

Other Names: Australasian Marsh-harrier, Gould's Harrier, Pacific Harrier, Pacific Marsh Harrier, Pacific Marsh-harrier, Swamp Hawk.

Circus approximans
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Distribution: Australasian/Oceanian. Southern NEW GUINEA, MELANESIA, AUSTRALIA, NEW ZEALAND, and POLYNESIA east to TONGA and FIJI. Introduced successfully to Society Islands. more....

Subspecies: Monotypic.

Taxonomy: Formerly considered to be conspecific with C. aeruginosus, and Wink and Sauer-Gürth (2004) confirmed that C. aeruginosus, C. ranivorus, C. spilonotus, C. maillardi, C. macrosceles, and this species form a monophyletic group, based on evidence from the mitochondrial cytochrome b gene.

Movements: Partial migrant (Bildstein 2006). In Australia, it breeds solely in the southern portion and Tasmania and winters in the northern portion and in southern New Guinea, vacating Tasmania entirely (Blakers et al. 1984). Post-fledging juveniles may disperse up to 1,500 km (Debus 1998), but many first-year birds oversummer in the south of the continent, and the population in southwestern Australia is sedentary (Baker-Gabb and Fitzherbert 1989). In New Zealand, juveniles disperse both north and south between the two main islands, and small numbers may arrive on islands as far as the Kermadecs (900 km NW), and then depart in spring (Oliver 1955). Birds in their second and third years that have not held a territory may also disperse during autumn (Baker-Gabb 1978, 1981). It also disperses widely in Fiji and Tonga and outlying islands, and the local name for it on Rotuma indicates periodic visits there (Watling 2001). Breeding adults are generally sedentary (Watson 1954, Robertson 1978). more....

Habitat and Habits: Typically seen flying low over open country, including lakes, swamps, wetlands, grasslands, coastal heaths, and croplands (Olsen 1995, Debus 1998). Roosts on the ground, often in large communal roosts of 20 to 200 birds in New Zealand (Gurr 1968) and, in Fiji, usually among long grass or sedges (Clunie 1984). Normally a solitary forager, but large groups sometimes congregate in areas of high food density in Fiji (Watling 2001). Also in Fiji, birds are sometimes seen over forest and open sea between "within-sight" islands (Watling op cit.). more....

Food and Feeding Behavior: Feeds on mammals, birds and their eggs, rats, reptiles, amphibians, fish, insects, and carrion (Clunie 1984, Debus 1998). Forages by low, slow quartering and soaring, and it seizes prey by diving or dropping to the ground or water surface, sometimes after hovering (Debus op cit.). It also harries waterbirds to exhaustion or sometimes drowns them, and it robs other raptors (Debus op cit.). more....

Breeding: Pairs nest solitarily or in loose "clumps" with other pairs, and the nest is a platform of sticks, reeds, grass, and other plants placed among tall grass, shrubs or reeds, either on the ground, in water, or, rarely, in a low bushy tree (Olsen 1995, Debus 1998). Clutch size is usually 3 or 4 bluish-white eggs (range 2-7), the incubation period is 33 days, and the nestling period is 43-46 days (Debus op cit.). The period of dependence after fledging lasts about four to six weeks. more....

Conservation: Common in suitable habitats. Categorized as a species of "Least Concern" by BirdLife International. 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.
Baker-Gabb, D.J. 1986. Ecological release and behavioural and ecological
  flexibility in Marsh Harriers on islands. Emu 86:71-81.
Clunie, F. 1984. Birds of the Fiji bush. Fiji Museum.
Debus, S.J.S. 1994. Pacific Marsh-harrier. P. 138 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.
Ferguson-Lees, J., and D.A. Christie. 2001. Raptors of the world. Houghton
  Mifflin, Boston, MA.
Fox, N.C. 1977. Some morphological data on the Australasian Harrier
  (Circus approximans gouldi) in New Zealand. Notornis 24:9-19.
Redhead, R.E. 1969. Some aspects of the feeding of the harrier. Notornis
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.
Watling, D. 2001. A guide to the birds of Fiji & Western Polynesia,
  including American Samoa, Niue, Samoa, Tokelau, Tonga, Tuvalu, and Wallis &
  Futuna. Environmental Consultants.

Sites of Interest:
Swamp Harrier photos.

Scott, Don

Last modified: 6/3/2010

Recommended Citation: Global Raptor Information Network. 2021. Species account: Swamp Harrier Circus approximans. Downloaded from http://www.globalraptors.org on 28 Nov. 2021

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