In 2010, the Bird Group of the Nature Society (Singapore) initiated a Small Bird Study Grant to encourage research on threatened birds species in Singapore. The grant of up to $2,000 would provide financial support to successful applicant to carry out research projects on these species in Singapore. Since its inception, we had awarded three grants to the following projects:
Tan Kok Hui for “The Study and Distribution of the Changeable Hawk-eagles in Singapore” in 2011. Ng Wen Qing for “Ecology interaction of Birds and Figs in Singapore ” in 2012. Felix Wong for “ Impact of the Introduced species like the Lineated Barbet and White-crested Laughingthrush on our native Birds”
This nest( left) taken at Faber Forest in April 2015 from across the road at Trade Hub by Klenn Koh. The Forest has since been cleared for a bus depot.
In this article, we provide a summary of Tan Kok Hui’s study of our Changeable Hawk-eagles Nisaetus cirrhatus across Singapore. Raptors in Singapore are generally not well studied, and the Changeable Hawk-eagle is no exception.. It is listed in the Singapore Red Data Book as a nationally threatened, uncommon resident. Being an apex predator, the Changeable Hawk-eagle is an indicator species of the health of our ecosystems. A decline in the population of its prey species, which includes anything from Plaintain Squirrels and Monitor Lizards to young Long-tailed Macaques would thus have detrimental impacts on the population of this large raptor.
Prior to 1992 there were no documented records of nesting of the Changeable Hawk-eagle in the whole of Peninsular Malaysia and Singapore. Our first confirmed nesting record of the species came in the early 2000s and it was regarded as a rare resident breeder then.
The subspecies limnaeetus that occurs in Singapore is the only one in the region that is polymorphic
Kok Hui’s project was successful in locating many nesting sites over one season of field work and thus was able to establish a new estimate of the Changeable Hawk-eagle population. In all he found six active nesting sites outside the nature reserves, mostly at the north-western part of the island ( e.g. Poyan, Neo Tiew, Mandai West, Woodlands). One nest each was found in south ( Mount Faber) and east ( Changi). The large nests were usually built with sticks on Albizia trees in secondary woodland since these are often the tallest trees around.
Three pairs of Changeable Hawk-eagle were also recorded away from these nest sites. They were at Sarimbun, Seletar Camp and the Singapore Quarry. Additionally, a few inactive nests were seen at Pasir Ris, Dairy Farm, Temenggong Road and Bukit Batok.
Based on the study, it can be concluded that there were at least nine nesting pairs of Changeable Hawk-eagles distributed in Singapore outside of the Central nature reserves. The present evidence collected by Kok Hui suggests that the Changeable Hawk-eagle is adapting well to Singapore’s landscape, especially the remnant areas of tall secondary woodland. To ensure that large raptors such as the Changeable Hawk-eagle can continue to survive in the urban jungle of Singapore, it is important that our remnant woodlands, especially those with stands of Albizzia (Falcataria moluccana) trees be retained and conserved for their biodiversity value.
Compiled by Alan OwYong and Yong Ding Li from Tan Kok Hui’s paper ” The Study and Distribution of the Changeable Hawk-eagles in Singapore 2011″. Many thanks to Klenn Koh for the use of his photo.