Bird Conservation International

Cambridge Journals Online - CUP Full-Text Page
Bird Conservation International (2009), 19:379-391 Cambridge University Press
Copyright © BirdLife International 2009
doi:10.1017/S095927090900851X

Research Articles

Is the Papuan Harrier Circus spilonotus spilothorax a globally threatened species? Ecology, climate change threats and first population estimates from Papua New Guinea


ROBERT E. SIMMONSa1 c1 and LEO A.T. LEGRAa2

a1 DST/NRF Centre of Excellence, FitzPatrick Institute, University of Cape Town, Rondebosch 7701, Republic of South Africa. Present address: Dept of Nature Conservation, Tshwane University of Technology, Pretoria 0001, Republic of South Africa.
a2 Wildlife Conservation Society, P.O Box 277, Goroka, Eastern Highlands Province, Papua New Guinea.
Article author query
simmons re [PubMed]  [Google Scholar]
legra lat [PubMed]  [Google Scholar]

Summary

We undertook a 3-week expedition to Papua New Guinea in April-May 2007 to assess the breeding, threats and population densities of the Papuan Harrier Circus spilonotus spilothorax and to determine a first global population estimate for this almost entirely unknown species. Two of the first nests known were discovered in April 2007 with three chicks each, in the eastern lowlands, in rank grass and reeds. The melanistic form of this subspecies was more common in the lowlands (< 1,500 m a.s.l) than in the highlands, but interbreeding of this and the typical form occurred in the lowlands. Movements of identifiable individuals through two highland grasslands indicated up to eight birds per day on passage, corroborating local knowledge that other raptors move into the highlands at the start of the dry season (April). Linear road counts indicated no harriers in the wooded highlands but up to 2.9 harriers 10 km−1 in lowland grasslands. Area counts gave an average of 6.5 harriers 100 km−2 in the grasslands and a breeding density of 1.21 nests 100 km−2. Given that preferred grassland and swamp habitat comprises c. 7% of the forest-dominated island of New Guinea, the global Papuan Harrier population can be no more than c. 3,600 birds and c. 740 breeding pairs. Wildfires peaked at 38 per month in the study area, occur throughout the dry season, and led to the loss of both nests. This suggests that many nests and prey may be lost at critical times and burning may be ultimately detrimental for the species. Grassland fires throughout Indonesia and Papua New Guinea are increasing with climatic warming and ENSO events, so we suggest that the Papuan Harrier may warrant a ‘Vulnerable’ conservation ranking due to small total population size and an accelerated reduction in habitat quality due to ongoing climate change.

(Received July 09 2008)

(Accepted December 10 2008)

Correspondence:

c1 Author for correspondence: e-mail; Rob.simmons@uct.ac.za