In search of Chinese Sparrowhawks wintering in southern Papua, Indonesian New Guinea
Rick Watson— 15 September 2011 — in Asia-Pacific Share
Editor’s Note: Wallacea is a region located almost entirely within the borders of Indonesia in southeast Asia, and includes the large island of Sulawesi, the Moluccas (Spice islands), Banda islands and the Lesser Sundas. The Lesser Sundas are located south of Sulawesi, and include Bali, Lombok, Sumba, Sumbawa, Flores and Timor. The Moluccas includes several hundred islands in the north-east of the Wallacea region, the largest being Seram and Halmahera.
Francesco Germi received a grant from The Peregrine Fund to perform a survey of the area. He submitted the following report.
Thirty years ago, the Tropics formed a mysterious realm into which migratory birds from northern climates disappeared for long periods. This was true perhaps nowhere more so than among the islands of Wallacea and Papua, Indonesia, where, for much of the twentieth century until the 1980s, there was virtually no active field ornithology. Recent migration counts notwithstanding, information on the ecology of migrants wintering in eastern Asia, in particular, and especially the Indonesian and Philippine archipelagos is still almost nonexistent. Even the most basic information on raptor migration in eastern Asia lags considerably behind that of Africa and the Neotropics. In the last two decades there have been considerably more observations of migrant raptors within Wallacea and raptors migrating into and out of Wallacea. For example our recent documentation of large numbers of diurnal raptors observed migrating eastwards over Bali and southwards over Sangihe into Wallacea begs the question where do these raptors spend the winter?
Prior to the observations of Ash in 1984 the only species of migrant raptor known to occur in any numbers in Wallacea were Chinese Sparrowhawk Accipiter soloensis and Grey-faced Buzzard Butastur indicus. Most other species at that time were either unknown in Wallacea or regarded as vagrants. Despite Ash’s characterisation of a discovery of “a spectacular migration of raptors [on Bali] ” the numbers he observed were actually very small by comparison to those we subsequently observed on Bali in 2004-5 and on Sangihe in 2007. Our combined autumn totals of migrant raptors counted moving east over Bali and south over Sangihe provides clear evidence that as many as about 400,000 raptors fly into Wallacea annually.
We now know that Chinese Sparrowhawks do NOT winter anywhere on the Asian mainland. This species, whose world population was estimated as “running into six figures,” actually winters on Sumatra, Java, Bali, Borneo, the Philippines and Wallacea. Our knowledge, however, for the Greater Sundas and the Philippines is largely anecdotal, and in the case of Borneo there is strongly divergent opinion as to whether this species winters there or not. Conversely, our studies on both Bali and Sangihe provide strong evidence that an estimated 350,000 Chinese Sparrowhawks enter Wallacea annually each autumn both through Bali in the west and Sangihe in the north. This total may represent as much as 80% of the entire world population.
The movement into Wallacea of such large numbers of Chinese Sparrowhawks contrasts with the paucity of records of this species in much of Wallacea and thus begs the question “Where do these birds go?”
As there are no comprehensive studies of this species anywhere on their breeding grounds, we have virtually no information on the habitat this species might utilise on their wintering grounds, what food they take, and how big their winter ranges may be.
Other than the anecdotal information from north Sulawesi there are very few observations of this species elsewhere on this island. Similarly, there are very few records of this species from the Lesser Sundas despite that we counted at least 350,000 Chinese Sparrowhawks over-flying Bali and Sangihe towards the islands of Wallacea. That the Chinese Sparrowhawk has been so uniformly ‘overlooked’ on Sulawesi away from the northern peninsula and throughout the Lesser Sundas suggests to us several possibilities:
Admittedly evidence for this scenario is currently sparse but then we have only just discovered that so many Chinese Sparrowhawks migrate into Wallacea each autumn. A handful of specimens and even fewer observations of this species, however, do provide some evidence that this species occurs further to the east in Wallacea. An even smaller number of specimens and observations provide further evidence of the presence of this species at the extreme western tip of New Guinea, in the Indonesian province of Papua.
New Guinea is a huge island (some might argue the world’s smallest continent!) and is still largely covered in primary forest. However, in the south of the island a vast area known as the Trans Fly ecoregion comes under the influence of a distinctly monsoonal climate and as a consequence supports an extensive mosaic of Monsoon Forest, extensive Tropical Savannah woodland, grasslands and freshwater marshes. Trans Fly habitats are notably more open than elsewhere on New Guinea and much of Wallacea. Furthermore, Trans Fly habitats appear to replicate fairly closely the preferred breeding habitats of Chinese Sparrowhawks. Thus the Trans Fly of southern New Guinea is potentially an ideal wintering ground for this migrant raptor species and possibly others. However, due to extensive seasonal flooding of this region there have been virtually no observations of birds in the Trans Fly during the period from November to April when they would be expected to be there.
Thanks to financial support from The Peregrine Fund and Hawk Mountain Sanctuary, I travelled to Papua (Indonesian New Guinea) in December 2010 to carry out a four-month field survey in the Trans Fly and adjacent areas, in search of wintering Chinese Sparrowhawks and other raptor species. I spent the first two weeks doing road transects in the Merauke region, including the spectacular Wasur National Park. However, surveys were hampered by torrential rains and large flooded areas, and most roads were impassable. Despite not seeing any Chinese Sparrowhawks, I knew that birds may have been overlooked owing to the difficulty of getting around in these areas.
In January, whilst depressing in the rain-soaked frontier town of Merauke, I heard rumor of a small missionary plane scheduled to fly to the remote Dolok Island, 200 km to the west. I knew that Dolok Island was pristine Trans Fly habitat, so after some begging with the local Catholic missionaries I managed to secure a seat on their plane, but with no assurance of a return date! So on a rainy January morning after being weighed on a scale together with my luggage, I boarded the small Pilatus aircraft heading into the uncharted territory of the oddly shaped Dolok Island. From the low altitude flight I was finally able to gaze over the vast empty wilderness of the Trans Fly savannas, an endless landscape of grassland and gallery monsoon forests, largely flooded. The huge Dolok Island (11,200 km²) is a vast mudbank outwash from the silt-laden rivers of the wild south coast of Papua. It is often forgotten because of its unprepossessing nature and isolation, and land travel is impossible due to the total lack of roads and seasonal heavy floods. I disembarked on a grassy airstrip and had to walk four kilometers under the tropical sun to reach the village of Kimaam, as no cars exist on Dolok, under the quizzically curious eyes of the villagers for the unusual sight. I was the only non-Papuan, the only white man in hundreds of kilometers, where local villagers spoke only the local languages—not Indonesian! Obviously there was no hotel to stay in Kimaam, so I managed to get a bed in a local house thanks to the help of the village school teacher, a young man from faraway Sulawesi. After the mandatory visit to the local “police station” (an unassuming hut in the middle of a marsh!) to show my surat jalan or travel permit, I was finally free to walk the flooded, muddy savannas around Kimaam in search of the Chinese Sparrowhawk…
What followed was days of daily treks in the mud, under the rain or the scorching sun, followed by scores of overexcited village kids, while I broadcast Chinese Sparrowhawk’s calls again and again in every direction, scanning every tree branch with my binoculars, and trying to explain to the bemused Papuan villagers what on earth I was doing there! Days passed without any sight of the elusive accipiter, throwing my confidence and morale to the bottom of the ubiquitous sea of mud.
And one day the feared but hoped radio call from Merauke arrived: the missionary plane was due to come back the day after. So the morning after, I packed up my backpack again, and I walked the four kilometers back to the landing strip, feeling defeated. But, I was just a few hundred meters from the airstrip when I noticed a familiar shape roosting on top of a light pole. My heart raced up to my throat, I pointed my binoculars and… yes, it was finally there! A male Chinese Sparrowhawk was roosting in front of me, the first record of this species 2,000 km to the east of its “known” wintering range, well into the depths of the remote Trans Fly, in the heart of Papua! A faraway engine noise broke the silence of Dolok Island, and a small dot appeared low in the sky. It was the missionary Pilatus aircraft coming to pick me up. Happy with my one sighting, I climbed aboard the plane determined to keep looking. My surveys continued through March 2011.
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