Status and distribution of hornbills in Thailand
by Ng Bee Choo, from Oriental Bird Club Bulletin 28, November 1998.
'A creature of such bizarre and extravagant appearance it seems less a living being than the product of some feverish Oriental fantasy. One of the world 's great natural treasures and at the same time one of nature's supreme oddities, it is that species of bird to which ornithologists have given the name Buceros bicornis: the Great Hornbill' - Richard Ives.
Pilai Poonswad began studying hornbills in Thailand after she became fascinated by them while acting as a guide to a BBC film crew in Khao Yai National Park when working on a documentary film entitled Fig Feast in Khao Yai. With Atsuo Tsuji she started to document the life of these birds and together they have spent more than 20 years studying this unique family. At first very little was known about hornbills and Pilai began her research by observing a Great Hornbill feeding in a fig tree and then, with the help of an assistant, tracing it back to its nest site. Now, hundreds of hornbill nests have been recorded and research sites have been set up to study the life history of these wonderful birds. Pilai's work has culminated with the organisation of the First International Asian Hornbill Workshop in 1992 and the Second International Asian Hornbill Workshop in 1996. Both were held in Thailand. The proceedings of the first workshop were published (1) in a Manual to the Conservation of Asian Hornbills and the proceedings of the Second Workshop, The Asian Hornbills: Ecology and Conservation, are in preparation and will be available soon.
Of the 31 Asian hornbill species (out of a world total of 54 species), 13 have been recorded in Thailand (2). In Asia, hornbills mainly live in monsoon evergreen forests or rainforests and their distribution and 1997 estimated population sizes in Thailand are indicated in Maps 1–4 (maps not in web version).
Hornbills nest in cavities in living trees such as Dipterocarpus sp. and Syzygium sp. They are unable to excavate their own nest holes and they must find available cavities, indeed, the availability of nesting cavities of an appropriate size is one of the population limiting factors. In Thailand hornbills begin searching for nest sites at the end of the monsoon season, in December or January. The male will locate a possible nest cavity and invite the female to inspect. Once she is satisfied with the choice of nest site, copulation occurs nearby. The female then seals herself inside the nest chamber using clay, rotten wood, regurgitated food and other materials supplied by the male. It usually takes three to seven days to complete this sealing process. The female lays her eggs, incubates them and then rears the chick inside the nesting cavity, the entire nesting process taking from three to four months. During this time the male feeds the female and later on supports the chicks as well. (Tickell's and Austen's) Brown, Bushy-crested and White-crowned Hornbills employ a co-operative breeding strategy. This means they have nest helpers, usually yearlings of the same family, to assist with the feeding of the female and the chicks.
Status of hornbills in Thailand
Oriental Pied Hornbill Anthracoceros albirostris Common
Black Hornbill Anthracoceros malayanus Threatened-extinct(?)
Rhinoceros Hornbill Buceros rhinoceros Endangered
Great Hornbill Buceros bicornis Vulnerable
Helmeted Hornbill Buceros vigil Endangered
(Tickell's) Brown Hornbill Anorrhinus (tickelli) tickelli Vulnerable
(Austen's) Brown Hornbill Anorrhinus (tickelli) austeni Vulnerable
Bushy-crested Hornbill Anorrhinus galeritus Vulnerable
White-crowned Hornbill Aceros comatus Vulnerable
Rufous-necked Hornbill Aceros nipalensis Endangered
Wrinkled Hornbill Aceros corrugatus Endangered
Wreathed Hornbill Aceros undulatus Vulnerable
Plain-pouched Hornbill Aceros subruficollis Endangered
Hornbill studies are being carried out at several sanctuaries. The list below gives some indication of the work being carried out and the population sizes and species present.
Huai Kha Khaeng Wildlife Sanctuary is situated in western Thailand and covers some 2,800 km2. Habitat types are diverse, comprising 47% tropical evergreen forest, 43% mixed deciduous forest, 6% dry dipterocarp forest, 3.5% mixed deciduous scrub and bamboo, and small areas of old clearings, non-forest and open water.3 Hornbill studies in this area have been carried out since 1990, and intensively since 1992. There are two study sites, the first of around 100 km2 at Nong Ma along the Huai Kha Khaeng river and the second of about 50 km2 at Khao Nang Ram/Khao Khieo. Currently there is a Woodpecker Study Project being conducted at Nong Ma which is focusing on the importance of woodpeckers in generating suitable nest holes for hornbills.
Intensive hornbill research has been conducted at Khao Yai National Park since 1980. The study area is around 70 km2 and contains 60 km2 of forest and 10 km2 grassland in the north-west sector the park. The habitat is mainly wet evergreen forest lying between 400 and 1,060 m. Dr Pilai Poonswad has estimated the population of hornbills in the study area as six per km2. The population of Oriental Pied Hornbills is relatively small in the study area because it is heavily forested and this is usually a forest edge species.
The estimated population of Wreathed Hornbills for the whole of Khao Yai National Park is 1,500 individuals, for Oriental Pied Hornbill about 1,000, for Great Pied fewer than 1,000 and for (Austen's) Brown Hornbill fewer than 500 individuals.
Budo and Hala-Bala is located at the southern tip of Thailand, close to the Malaysian border. Both are newly protected areas and were, until recently, controlled by Muslim separatists. Even now they are not always considered safe. Studies in this area began in 1994 and the ongoing research is concentrating on nesting records. Hornbills here are severely threatened because the local villagers are poaching the chicks to sell as pets or to eat them.
Threats to hornbills and future conservation of hornbills Hornbill populations are declining. The major threat is from rapid loss of habitat through deforestation, but hornbills are also threatened by poaching of chicks for food and for the illegal wildlife trade. Animal traders are willing to pay large sums of money for hornbill chicks. Poaching of chicks is considered to be an important threat in southern Thailand.
The Hornbill Research Foundation has set up a Hornbill Family Adoption Program. This aims to raise funds to provide extra income for villagers to protect any nesting hornbills they find and collect data on them. For details of how to adopt a hornbill family, please contact the Hornbill Research Foundation, c/o Department of Microbiology, Faculty of Science, Mahidol Unversity, Rama 6 Road, Bangkok 10400, Thailand. Tel. +66 2 246 3026 ext. 4606, fax +66 2 644 5411.
Acknowledgements The author is grateful to Dr Pilai Poonswad for providing the data for this article. Without her dedication, determination and hard work, this information may never have been collected. The author also thanks Vijak Chimchome, Boonma Seangthong, Adisak Vidhidharm, Sudjai Nuttaro, Narong Jirawatkavi, Siriwan Nakkhuntod, Kamol Plongmai, Phitaya Chuailua, Preeda Thiensongrassamee, Panya Suksomkit, Rungsrit Kanjanvanit for their work and support. Without them, the amount of research would have been far less. Many people have helped the Hornbill Project Thailand and the Hornbill Research Foundation over the years and the Royal Forest Department Thailand has for many years supported the Hornbill Project. We are grateful to them all for their assistance.
Poonswad, P. & Kemp. A. C. (1993) Manual to the conservation of Asian hornbills. Hornbill Project, Mahidol University, Bangkok.
Kemp. A. C. (1995) The hornbills: Bucerotiformes. Oxford University Press, Oxford.
Bunyanupub, J. (1997) Application of LANDSAT 5 (TM) Imagery for Land Use Studies of Huai Kha Khaeng Wildlife Sanctuary, Uthai Thani and Tak Province.
Chimchome, V. (1996) Biology and ecology of two endangered species: Rufous-necked and Plain-pouched Hornbills in Huai Kha Khaeng Wildlife Sanctuary. Report submitted to Pro Natura Foundation-Japan.
Poonswad, P. (1993) Comparative ecology of sympatric hornbills(Bucerotidae) in Thailand. PhD thesis, Osaka City University.