Winged migration

Continuing our Innovation series, Life talks to a research team for raptor migration on Khao Dinso in Chumphon where their work is crucial for future conservation projects

Andrew J Pierce of King Mongkut's University of Technology Thonburi is the project leader for the satellite tracking system. Desmond Allen

On a raised wooden platform on Khao Dinso, a 350m-high hill along a coastline of the Gulf of Thailand in Chumphon province, a group of international birdwatchers are waiting to see raptor migration since dawn's break. Every year about a million birds migrate during autumn from cold lands in Russia or China, passing Khao Dinso in Thailand to the tropical islands of Indonesia to find food.

The annual natural phenomenon starts from the middle of August to November. It attracts visitors from many parts of the world like those on the watch. They are from England, New Zealand, Australia and Finland.

"Khao Dinso is one of the world's best migratory raptor observation sites," said Chukiat Nualsri, chairman of Khao Dinso Natural Study Foundation.

Thanks to its geographic features that funnel migrating raptors and birds through the isthmus of Kra, or kho khod kra in Thai, the narrowest part of Thailand and southern part of Myanmar, to the South. It is because migratory raptors tend to fly overland where they can stop for food and rest instead of passing over large bodies of water like ocean and sea.

In other parts of the world, billions of birds migrate yearly from their breeding grounds in the North when temperatures start to drop to the South and return to their habitats for breeding in spring. Five flyways known for major long-distance raptor migration are Trans-American (North America-Central/South America), West European-West African, Eurasian-East African, East Asian Continental and East Asian-Oceanic flyways.

Thailand is part of the East Asian Continental flyway.

"From the viewpoint of Khao Dinso, we can spot 38 out of 56 species of hawk that are found in the country," said Chukiat, adding the commonly seen raptors are Chinese sparrowhawk, Japanese sparrowhawk, Oriental honey buzzard, black baza and shikra.

Chukiat initiated the activity to watch raptor migration in Chumphon in 2002. At that time he was a permanent secretary of Na Thung Municipality in Chmphon's Muang district.

"I've watched raptor migration since I was young. I've always been fascinated by observing thousands of birds flying over Chumphon's sky every day. When I learnt about the raptor watch activity in Malaysia [which is organised in Melaka in March when they head back to their habitat], it made me think of having the same activity in Thailand," he said.

Chukiat worked with Dr Kaset Sutasha, chairman of the Bird Conservation Society of Thailand, to kick off the raptor watch in the city. In 2009, they moved the watch site to a better spot on Khao Dinso. Since that year, the raptor watch has been promoted as an co-tourism event for the province that attracts visitors from Thailand and abroad.

Black kite. Chukiat Nualsr


Khao Dinso is also a vantage point to monitor the migratory birds. The Bird Conservation Society of Thailand has a team of dedicated volunteers to watch the sky and record a number of migrating raptors and birds daily. They jot down bird species, identify genders and even record if the birds are adult or juvenile. They take note of wind direction, wind speed, barometric pressure and temperature every hour starting from 7am to 5pm, from Aug 15 to Nov 15.

The data is crucial for research. The information is also daily updated on the Facebook page of the Flyway Foundation (, a non-profit institution that supports research and education of wildlife conservation in Thailand.

"Although Khao Dinso is not a watch site where we can see a million raptors a day, it is a prime site where we can spot up to 26 species of raptors in one day," said Dr Kaset Sutasha, chairman of the Bird Conservation Society of Thailand and head veterinarian of the Avian and Exotic Pet Clinic, Faculty of Veterinary Medicine of Kasetsart University.

"It is important to monitor raptor migration because birds of prey are at the top of the food chain. They are an indicator of healthy biodiversity in their natural habitat," he said.

"If we see a large number of adult hawks passing Khao Dinso a bit early or around the middle of August instead of the middle of September, it can imply that they failed to breed that year due to threats such as habitat loss," he said.

To know of their whereabouts after passing Khao Dinso, a bird ringing operation was launched in 2011. The research project was a joint venture among researchers from Mahidol University led by Assoc Professor Philip D Round, Khao Dinso Natural Study Foundation, the Bird Conservation Society of Thailand and the Department of National Parks, Wildlife and Plant Conservation.

The research team trapped migrating birds and recorded biodata including length and weight, and took blood samples for disease testing. They put an ID ring on a lower leg of the birds. Over the past eight years, the research team has trapped and banded about 300 migratory birds including raptors and other species like paradise flycatchers, Eastern crowned warblers, orange-bellied flowerpeckers and Siberian blue robins. However, they have never recaptured those birds so far.

The researcher team needed more advanced technology in order to know more about the migratory birds, especially locations where they spend autumn and where their habitats are.

Oriental honey buzzard. Chukiat Nualsri


As part of the research team, Andrew J Pierce of Conservation Ecology Group of King Mongkut's University of Technology Thonburi brought in new technology -- a satellite telemetry tag.

"Half-a-million birds pass [Khao Dinso yearly], we didn't know much about what happened after they passed us and that's what we want to know," said Pierce.

Funded by the National Science and Technology Development Agency (NSTDA), the tracking device is based on the Advanced Research and Global Observation Satellite (Argos) system. The satellite-based tracking tag for migratory birds is a tiny device that weighs less than 5g, he said. It is tied on the bird's wings like a backpack. Each tag is powered by solar panels that can transmit signals in real time. The research team can follow the birds' locations by checking their computer.

The team attached the devices to four Chinese sparrowhawks and four Japanese sparrowhawks. The two raptor species were selected because they were regularly seen and caught. The team picked only adult females because their size was bigger than the males. Each bird must also weight at least 150g.

"We don't want them to carry anything more than 4% of their body weight otherwise they might have a problem during migration," he said.

Benefits of the satellite tracking system mean that the device can last several years. It can give the real time location of the migratory birds and the accuracy is within a 1km radius. But the technology comes with a premium price.

"We only have eight devices because they are really expensive," he said, adding that one tracking device costs more than US$4,000 (about 120,000 baht).

Data from the Argos system indicates that the raptors can fly 40kph. In one day, they fly 150-200km or up to 400km depending on weather conditions. They feed in the morning or the evening and fly only during the daytime.

"We learnt where they went. We also learnt that when they arrived where they're going in winter, they just stayed. They didn't go more than 1km from the point where they arrived for four months. We didn't expect that. We thought they stopped here and moved. But no. Then they came back almost the same way, but probably passing further to the west," he said.

From Khao Dinso, the four Chinese sparrowhawks flew to four different destinations including North and South Sumatra, East Nusa Tenggara, which is the southernmost province of Indonesia, and Viqueque in Timor Leste.

For the Japanese sparrowhawk, one flew to Pahang in Malaysia before the signal was lost. One flew to Sabah in Malaysia while the other two went further to Bangka Island and Central Kalimantan in Indonesia.

Crested serpent eagle. Chukiat Nualsri


Although all signals were gone last year, the research team could record a complete flyway of one Chinese sparrowhawk and one Japanese sparrowhawk.

The Chinese sparrowhawk named Fern flew further south from Khao Dinso, passed Indonesia and stayed in Timor-Leste from Nov 9, 2017, to March 8, 2018. It flew back by passing Indonesia to the Andaman Sea, Chiang Rai and Laos before returning to its habitat in Guangxi in China.

Fern stayed in China for nesting and breeding from May 18 to Sept 7, 2018, when it started the migration down south, passing Khao Dinso again. The total flying distance is 14,532km.

"It is hard to believe that a raptor which weighs equal to a small milk carton took that long migration route. The flying distance was longer than the Earth's diameter [about 12,756km]," said Dr Kaset.

For the Japanese sparrowhawk, the research team tracked one named Chom to its habitat in Amur, the far eastern province in Russia.

From Khao Dinso, Chom flew to Bunga Island in Indonesia and stayed from Oct 12, 2016, to April 2, 2017. It flew back 7,699km within 53 days to Amur in Russia on May 24, then the signal was lost.

"The raptor didn't pass Japan. We always believed that migratory Japanese sparrowhawks had their breeding grounds in Japan. But we learnt from this research that ornithologists have been wrong for more than a century. It was the first time we knew the raptor had its habitat in Russia, not in Japan," said Dr Kaset.

"There are Japanese sparrowhawks in Japan, but the birds do not migrate. They both look alike, but our DNA lab test shows amazing data, that they have different types of DNA."

"From this research, we discovered a new subspecies of sparrowhawk," added Dr Kaset, adding that the findings will be reported and the bird may be renamed, perhaps during the coming International Ornithologists Congress in 2020.

Although research on the Chinese and Japanese sparrowhawks was completed last year, the team continued studying bird migration. This year, the team self-funded two satellite tracking devices.

Team leader Andrew J Pierce expects the tracking technology will be more affordable and smaller in the future. He wants to track adult male Japanese and Chinese sparrowhawks, or even other smaller types of migratory birds.

"It is important that we know their habitat and where they go. If it turns out that they need a particular habitat, we can conserve them in those countries along their flyways. It's important to know what the birds want before it's too late," said Pierce.

Raptor watch chronology

2002: Raptor watch began in the city of Chumphon.

2009: The watch site is moved to Khao Dinso, a 350m hill along Thung Wua Laen beach in Pathiu district, about 20km northeast of the city.

2010: The three-month project to count raptors and other birds during autumn migration begins and continues today.

2011: The banding project on migratory birds starts. Over the past eight years, about 300 raptors and birds get ID rings. None of the birds is ever recaptured.

2012: The Chumphon Raptor Migration and Education Centre is opened in Khao Dinso. It is known as the first centre for raptor research and education in Southeast Asia.

2016-2017: Satellite telemetry project is implemented. With financial support from the National Science and Technology Development Agency, the research team attaches satellite tags to four Chinese sparrowhawks and another four Japanese sparrowhawks.

2018: The complete migration route is recorded. The team finds the Chinese sparrowhawk flew almost 15,000km. The team also discovers a Japanese sparrowhawk has its habitat in Russia, leading to the discovery of a new subspecies.

2019: The raptor watch and count runs from Aug 15 to Nov 15 yearly. Satellite tracking research also continues with two more tags this year.

Chinese sparrowhawk. Chukiat Nualsri

The viewpoint on Khao Dinso in Chumphon.

Dr Kaset Sutasha, chairman of the Bird Conservation Society of Thailand. National Science and Technology Development Agency

Chukiat Nualsri, chairman of Khao Dinso Natural Study Foundation. National Science and Technology Development Agency

A raptor wears a satellite tag that weighs about 4% of its body mass. Desmond Allen

Researcher measures and records biodata. Desmond Allen

Japanese sparrowhawk. Chukiat Nualsri