Written by Richard W. White & Goh Yew Lin
On the morning of 15 April 2023 RWW and GYL visited Sungei Buloh Wetland Reserve (SBWR) for birding. The tide was falling and after crossing the main bridge over Sungei Buloh Besar, we started a clockwise circuit of the Migratory Bird Trail.
At around 08.30 we reached Platform 2, overlooking Sungei Bilabong Buloh. Here we saw a Lesser Adjutant perched in the crown the mangrove trees on the opposite bank of the creek. Soon after the initial sighting, the bird grabbed a twig from the canopy and flew off carrying it. The bird did not fly far, and could be glimpsed (although mostly obscured) moving around in the canopy.
Shortly after, it returned to the area of the original sighting where it proceeded to pick another twig. At this time, a second bird arrived and interacted with the bird collecting nest material. The first bird flew off carrying a twig, while the second bird then also collected a twig. Around the same time, other birds came into view and at one time we could see 4 Lesser Adjutants in close proximity to one another.
We can see no other explanation for this behaviour other than collecting nest material.
Lesser adjutant is a former breeder in Singapore, although there have been no breeding records in the nation since about 1940 (Wang & Hails, 2007). No reasons are given for the local extinction of this species. Until recently it was considered a scarce, or even rare, resident in Singapore, although the status of the species within the restricted access Western Catchment area remains uncertain. As recently as 2016 some birders chartered a boat specifically to search for this species (Francis Yap pers. comm.). Since then, it has become increasingly regularly seen at several sites in the north-west of Singapore, centred on the SBWR and Kranji area, with a peak count of 18 in January 2023.
While it was extinct in Singapore, populations continued to breed in Malaysia and Indonesia (Sumatra). It is not clear which of these populations the re-colonisation of Singapore can be attributed to.
This note is intended to raise awareness of the likelihood that, after a gap of more than 80 years, this species will soon be breeding again in Singapore (if indeed it is not already).
References
Wang, L. K., & Hails, C. J. (2007). An annotated checklist of the birds of Singapore. Raffles Bulletin of Zoology Supplement, 15, 1–179. Link
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While it is unusual to draw attention to potentially active nests; after due consideration the Singapore Bird Project has decided to make an exception on this occasion.
In part, we hope that increased observer coverage will help to document any breeding attempt and associated behaviours. We have also taken into account the remote and inaccessible nature of the area where the birds appear to be nesting, which means that the prospect of disturbance by observers is effectively zero.
We welcome any feedback on this decision.