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Papuan Harrier
Circus spilothorax

Status: Lower risk

Population Trend: Stable.

Other Names: Eastern Marsh Harrier, Papua New Guinea Harrier, Spotted Marsh Harrier, Spotted Marsh-harrier, Spotted-backed Marsh Harrier

Circus spilothorax
click to enlarge
Distribution: Australasian. Endemic to central and eastern NEW GUINEA. more....

Subspecies: Monotypic.

Taxonomy: Regarded as a subspecies of the Eastern Marsh Harrier, Circus spilonotus by Brown and Amadon (1968), Orta (1994), Ferguson-Lees and Christie (2001), and BirdLife International (2010), but treated as a full species here, following the recommendations of Coates and Peckover (2001) and Simmons (2000, 2010). The latter arguments were based on plumage differences, the lack of immigration of Circus spilonotus from the north, and the resident status of C. spilothorax. Tissue samples were collected for DNA analyses from several individuals of C. spilothorax in 2007 (Simmons and Legra 2009), and the results of this study will be reported shortly by Prof. Michael Wink and Rob Simmons.

Movements: Simmons and Legra (2009) documented altitudinal movements of this species from lowland to highland grasslands in April at the beginning of the dry season. Local residents in villages around Goroka, a town at 1,500 m in the Eastern Highlands, reported that the species is only present there from April to September. Hoogerwerf (1964) noted that this species is absent from the southern lowlands around Kurik from May-September (dry season), but present in all other months over a four-year period.

Habitat and Habits: Frequents large grasslands, floodplains, and vegetation fringing wetlands, and other open country; usually seen soaring or flying low over open country or swamps, mostly in the highlands (Coates 1985, Beehler et al. 1986). Simmons and Legra (2009) and Simmons (2010) saw birds foraging over semi-burned grassland and thought that they were attracted to burning areas along with Black Kites. Simmons (op cit.) observed birds foraging close to modern buildings and towns, as well as near traditional villages in the highlands. This species usually occurs singly, or occasionally in pairs (Coates and Peckover 2001). Rand and Gilliard (1967) stated that it is wary and difficult to approach. more....

Food and Feeding Behavior: Feeds on small mammals, birds, and lizards (Coates 1985, Coates and Peckover 2001). Simmons (2010) studied this species in the Eastern Highlands and analyzed prey strikes, prey remains, and pellets recovered from nests or perch sites, and he found that the diet consisted mostly of birds and bird eggs. Identified prey species included quail and their nest contents (Coturnix sp.), Lewin's Rail (Rallus pectoralis), mannikins (Lonchura sp.) and Pied Chat (Saxicola caprata) or Willie Wagtail (Rhipidura leucophrys). Rats, a mouse, and a frog were also recorded as prey, with birds comprising 72$% of the diet, small mammals 22%, and the frog at 6%. Simmons (op cit.) thought that these harriers may also pick up dead or immobilized amphibians on airstrips. He noticed that this species typically flies about 4-5 m above grasslands and wheels and stoops on prey, rather than striking rapidly from lower altitudes like other harriers. more....

Breeding: The nest is placed on the ground like those of other harriers. R. Campbell (in Coates 1985) observed a pair carrying nesting material in grassland at Kagamuga, near Mt. Hagen, during 26-28 March 1978. Mating was observed on 27 March, and when the nest was found on 10 May, it contained two well-grown young and an addled egg. The egg was spherical and white, measuring 46.5 x 37 mm. Simmons and Legra (2009) and Simmons (2010) reported on two nests found in April 2007 in the eastern lowlands. Both were on the ground adjacent to reed dumps about 1 m high, which stood slightly above the surrounding grasses, and each contained three chicks. An egg measured 49.18 mm x 43.17 mm (Simmons 2010), considerably larger than the one reported earlier (Coates op cit.). Laying dates of first eggs were estimated at 2 and 6 April, respectively, which is at the beginning of the dry season.

Conservation: Both nests found by the Simmons and Legra (2009) field team were destroyed by grass fires, suggesting that many nests and prey may be lost at critical times in the breeding season. The incidence of grass fires will probably increase as a result of climate warming and ENSO events. Based on this evidence and the apparently small size of the global population, Simmons and Legra (op cit.) recommended that the Papuan Harrier should be regarded as Vulnerable. BirdLife International treats the Papuan Harrier as a subspecies of the Eastern Marsh (Pacific) Harrier, Circus spilonotus, which it categorizes globally as a species of "Least Concern."

Population Estimates: Based on their three-week survey in April-May 2007 to assess the population density of the Papuan Harrier and the extent of its preferred habitat, grasslands and swamps, Simmons and Legra (2009) estimated that the global population probably does not exceed 3,600 birds and 740 breeding pairs, with a range of 2,552 to 4,050 birds. Simmons and Legra (op cit.) estimated that the grasslands and swamp habitat that this species prefers comprises only 7% of the island of New Guinea. Based on two confirmed nests and two other suspected pairs in the same area, Simmons and Legra (op cit.) estimated a minimum nesting density of 1.33 active nests per 100 kmē and a potential nesting density of 2.67 nests per 100 kmē. Roadside surveys in the lowland Ramu and Markham Valleys yielded linear densities varying between 0.9 and 2.9 birds per 10 kmē.

Important References: 
Beehler, B.M., T.K. Pratt, and D.A. Zimmerman. 1986. Birds of New Guinea.
  Princeton University Press, Princeton, NJ.
Coates, B.J. 1985. The birds of Papua New Guinea, including the Bismarck
  Archipelago and Bougainville. Vol. I. Non-passerines. Dove Publications,
  Alderley, Queensland, Australia.
Coates, B.J., and W.S. Peckover 2001. Birds of New Guinea and the Bismarck
  Archipelago: a photographic guide. Dove Publications, Alderley, Queensland,
Diamond, J.M. 1972. Avifauna of the Eastern Highlands of New Guinea.
  Publications of the Nuttall Ornithological Club no. 12.
Ferguson-Lees, J., and D.A. Christie. 2001. Raptors of the world. Houghton
  Mifflin, Boston, MA.
Orta, J. 1994. Eastern Marsh-harrier. Pp. 137-138 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.
Rand, A.L., and E.T. Gilliard. 1967. Handbook of New Guinea birds.
  Weidenfeld & Nicolson, London.
Simmons, R. 2000. Harriers of the world: their behaviour and ecology.
  Oxford University Press, Oxford, UK.
Simmons, R.E. 2010. The nest, eggs, and diet of the Papuan Harrier from
  eastern New Guinea. Journal of Raptor Research 44:12-18.
Simmons, R., and L.A.T. Legra. 2009. Is the Papuan Harrier Circus
  spilonotus spilothorax
a globally threatened species? Ecology, climate
  change threats and first population estimates from Papua New Guinea. Bird
  Conservation International 19:379-391.

Sites of Interest:
Papua New Guinea Harrier research
Details on current research on this little known species.
Papuan Harrier photos (filed under Eastern Marsh Harrier).

Legra, Leo

Last modified: 8/3/2015

Recommended Citation: Global Raptor Information Network. 2020. Species account: Papuan Harrier Circus spilothorax. Downloaded from http://www.globalraptors.org on 4 Jul. 2020

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