- Circus spilothorax
47-61 cm, a large harrier
- Upperside mostly grey
- Black streaking on crown and neck
- Black lesser and medial coverts and primaries
- Underside mostly pale
- Black on primaries and primary coverts
- Throat streaked black and white or in central highlands solidly black
- Upperside brown with paler rump and some banding on tail
- Underside paler, on body heavily streaked with reddish brown
- Wing underside mostly pale with coverts heavily spotted and barred in reddish brown
A dark morph of the male is mostly dark grey to blackish with just a few paler areas such as some streaks and primary windows.
This species has been split from Eastern Marsh Harrier
Open habitats including grassland, swamps, floodplains and wetlands, and specifically for foraging also attracted to agricultural areas and burning areas.
Nests on ground among tall grasses.
- Clements, J. F., T. S. Schulenberg, M. J. Iliff, S. M. Billerman, T. A. Fredericks, B. L. Sullivan, and C. L. Wood. 2019. The eBird/Clements Checklist of Birds of the World: v2019. Downloaded from http://www.birds.cornell.edu/clementschecklist/download/
- del Hoyo, J., N. Collar, and J. S. Marks (2020). Papuan Marsh-Harrier (Circus spilothorax), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.easmah2.01
- BirdForum Opus contributors. (2021) Papuan Harrier. In: BirdForum, the forum for wild birds and birding. Retrieved 21 April 2021 from https://www.birdforum.net/wiki/Papuan_Harrier