Observers track migration of birds of prey through Java

By Paul Jepson

BOGOR, West Java (JP): A network of observers is tracking the southward migration of birds-of-prey into Java and East Indonesia. For many years ornithologists have known about the October passages of buzzards and hawks across the straits between East Java and Bali. But it was only in 1995 that staff of BirdLife International discovered that these birds were funneling over the Puncak Pass on their way through Java. This finding has inspired a desire to know more about migratory routes and the numbers and species involved.

BirdLife's Iwan Setiawan, who is coordinating an initiative called Raptor Migration in Haze Condition, points out that there is a more serious purpose to these surveys.

"We are worried that fires in Sumatra and Kalimantan may disrupt bird migration. Our surveys aim to assess whether migratory fly-ways cross fire risk zones and if birds become disorientated when they meet smoke or haze. An e-mail group of observers in Japan, Taiwan, Malaysia, Singapore and Indonesia is sharing information to answer these important questions."

Iwan has mobilized local bird clubs to conduct watches throughout October at 12 sites from Sumatra, east across Java to Bali. One of the most active of these clubs is the Cibodas Bird- watching Association (CIBA).

"We started counts at the Puncak Pass on Oct. 6, but the large movements did not start until around the 16th," says the club's director, Adam A. Supriatna.

"We are now counting about 500 birds a day and expect this peak to continue for about three weeks until early November".

Last month, I joined Richard Grimmett, head of BirdLife Asia and a leading expert on bird-of-prey identification at the Puncak observation point, just above the Rindu Alam restaurant.

At about 9 a.m. we watched a flock of 80 or more raptors spiral up on a rising thermal from their night-time roost in a forest patch in the tea plantation. After pointing out the five large birds as Honey Buzzards, he explained the difficulty of identifying smaller sparrowhawks that made up the bulk of the flock.

"About 80 percent of the birds we identify are Chinese Goshawks but most go over too high to be certain. The other species is Japanese Sparrowhawk. This is identified by blunter wings and barred under-wing, but a good view is required to be sure of identification."

He went on to say: "These are birds moving down from their breeding grounds in East Russia, Northeast China and the Korean Peninsula. We think they migrate down the Bukit Barisan range of Sumatra taking advantage of up-drafts off the mountains but their final destination beyond Bali is not clear."

Estimating numbers is difficult. Vincent Nijman, who has made a special study of bird-of-prey in central Java notes: "We counted 2,800 passing through the Dieng Mountains of central Java last week, but they are clearly moving over a broad front and we are only seeing a proportion of the birds moving."

The Sumatra-Java-Bali fly-way is not the only migration route into Indonesia.

Jim Wardill of the conservation project Action Sampiri, which is based on the remote Sangihe island in North Sulawesi, says: "We have long suspected that birds of prey island-hop south through the Philippines and the Sangihe-Talaud archipelago into North Sulawesi. Last year we confirmed this by counting 2000 migratory hawks passing through Sangihe."

According to these experts there is some evidence that the fires and El Nino droughts of the last two years may have disrupted the migration, but there is no evidence of any decline in numbers. Importantly, these surveys highlight the need for careful siting of power lines in migratory bottle-neck areas and protection of forest at critical points along the flyway.

"Large numbers of birds-of-prey roost and hunt for food in a small patch of forest just below the Puncak Pass in the Telaga Warna tea plantation. It is a critical stop-over site on their migration. We are working with plantation worker communities to ensure protection and restoration of this forest," said Adam Supriatna.

CIBA's work will help ensure that migrating birds-of-prey find a safe haven to rest on their long journey east and that bird- watchers can continue to enjoy the wonderful spectacle of flocks of these magnificent birds spiraling upwards and over the pass.

The writer is a consultant in several institutions, including the BirdLife International.