Papua Harrier papers
Congratulations to Rob Simmons for his peer-reviewed papers on the worlds most elusive harrier!
Pair together over floodplain A 3-week expedition to Papua New Guinea in April-May 2007 has document the first nests and eggs of the world’s most poorly known harrier – the Papuan Harrier of New Guinea. This species, endemic to the world’s third largest island is (erroneously) lumped as a subspecies of the more common Eastern Marsh Harrier (Circus spilonotus) of the Russian mainland. The lack of any DNA material for this species led Rob Simmons to journey from Cape Town to PNG to join raptor expert Leo Legra to look for the species in the highlands and lowlands of this tropical island.
We discovered two of the first nests known in April 2007, both with just-hatched chicks, in the eastern lowlands of PNG. Both nests were found in river flood plains in rank grass and reeds very well hidden from the sun and humans alike. Measurements of one egg revealed a very large volume – and since egg volume and female body size are closely related, the birds laying them may be world’s largest harrier. DNA was collected from the chicks but that still lies in PNG due to permitting. The timing of the trip had been crucial and we guessed from one other egg that the start of the dry season would be the start of the breeding season. We were fortunately correct but that came with a major problem – fire.
The second stage of the project was to estimate first-order population size and record any threats. We determined populations in highland areas by linear road counts, but they indicated no harriers in the wooded highlands. Harriers were only encountered again in the lowlands (in the Ramu Valley) where about 2.9 harriers/10 km occurred. By focussing on a known study area of 150 km2 we found that about 6.5 harriers occurred for every 100 km2 of grasslands at a breeding density of 1.21 nests/100 km2. Since only about 7% of forested New Guinea supports the preferred grassland and swamp habitat, the population can be no more than ca. 3,600 birds and ca. 740 breeding pairs.
Both nests, however, were lost to wildfires that occur throughout the dry season and peak at 38/month in the study area. This suggests that many nests and prey may be lost at critical times and grassland fires throughout Indonesia and Papua New Guinea are increasing with climatic warming and ENSO events. Our conclusion was that the Papuan Harrier may warrant a ‘Vulnerable’ conservation ranking due to the small total population size and an accelerated reduction in habitat quality due to ongoing climate change.
Two papers have arisen from this work, partially supported by Natural Research :
SIMMONS RE. 2010. The nest, eggs and diet of the Papuan Harrier from Eastern New Guinea. J Raptor Research 44 (1): 12-18.
SIMMONS, RE, LEGRA LAT. 2009. Is the Papuan Harrier a globally threatened species? Ecology, climate change threats and first population estimates from Papua New Guinea. Bird Conservation International 19:1-13.