Sungei Buloh Wetland Reserve just celebrated its 25th anniversary this year as the premier stop over site for migratory shorebirds in Singapore. But we were concerned for its future as the Mandai Mudflats and Mangroves further east was delisted from the Singapore Green Plan (2012). The government had announced plans to reclaim the mudflats. The visiting shorebirds depend on Mandai Mudflats to refuel during its stop over. They then fly to Sungei Buloh to roost during high tides. To show this connection, Sungei Buloh Wetland Reserves and NParks in 2011 initiated a study of the movement of shorebirds between the Mandai Mudflats and Sungei Buloh. The Bird Group of the Nature Society was invited to be part of the study which we gladly accepted. This was a first of its kind systematic study to determine that the visiting shorebirds that feed at Mandai Mudflats fly back to Sungei Buloh to roost.
Mandai Mudflats and Mangroves at low tide. It is part of the Kranji-Mandai IBA, Important Bird and Biodiversity Area. Two Horseshoe Crab species are found to be breeding here.
A total of six sessions were conducted between 28 November 2011 and 9 March 2012. Teams of 2 to 3 observers were stationed at Sungei Buloh, Pang Sua Estuary and in a boat at the Straits of Johor mid way along their flight path hours before the respective high and low tides. We did not managed to be at Mandai Mudflats for all the sessions due to lack of observers. The numbers and time of each species taking off, landing and flying past each station were recorded. A good collegation was when most of the same species were recorded at the respective stations at around the same time.
Teams locations A-SBWR, B- Boat in Johor Straits, C-Pang Sua Estuary, D-Mandai Mudflats.
The results were what we expected. During four high tide sessions, 200, 205, 241 and 177 Whimbrels Numenius phaeopus were recorded at all the stations flying from Mandai back to Sungei Buloh to roost. At the other two low tide sessions, 215 and 240 Whimbrels were recorded flying back to Mandai from Sungei Buloh to feed. These counts confirmed that high numbers of Whimbrels that feed at Mandai Mudflats returned to Sungei Buloh and vice versa.
Good numbers of Whimbrels that feed at Mandai flew back to Buloh to roost.
Next were the Common Greenshanks Tringa nebularia. For the four high tide sessions, 50, 8, 62 and 60 flew from Mandai to Sungei Buloh and 57 and 93 flew out of Sungei Buloh back to Mandai/Pang Sua to feed during the two low tide sessions. Most of the Common Greenshanks that feed at Mandai returned to Sungei Buloh and vice versa, except for one session.
Pacific Golden Plovers flying over Johor Straits on their back to Sungei Buloh and fish farms to roost.
We monitored the movements of the Pacific Golden Plovers, Pluvialis fulva and Lesser Sand Plovers Charadrius mongolus as well. But we only managed to record one collegation of 130 Lesser Sand Plovers flying from Mandai to Sungei Buloh at high tides and two records for the Pacific Golden Plovers, 40 from Mandai to Buloh at high tide and 75 from Buloh back to Mandai at low tide. The reason for this was that some of the Lesser Sand Plovers flew over to the Danga Bay, Johor to roost while the fish farmers reported large numbers of Pacific Golden Plovers roosting on their fish farms at high tides.
We had two interesting findings during the study. The Pang Sau estuary just west of Mandai was just as important as a feeding ground for the shorebirds as Mandai. Thankfully this estuary will form part of the nature park. Not all the Common Redshanks left Buloh at low tides. Many preferred to stay at Buloh to feed and roost.
The then Singapore Branch of the Malayan Nature Society had identified the Mandai Mudflats and Mangroves as “Top priority” in the Master Plan for Conservation of Nature in Singapore 1990 and the present Nature Society (Singapore) had been advocating for its protection ever since. The Bird Group carried out the first Annual Bird Census (ABC) there in April 1986 and added the Asian Waterbird Census (AWC) in 1990. Both censuses are still on going without any breaks. The data collected have been shared with NParks and other organisations. We are delighted that Mandai was finally designated as a Nature Park on 17 October 2018. We would like to think that censuses and studies like these play a small part in achieving this outcome.
- Study Team: Sharon Chan, David Li, Mendis Tan, Bari Mohamad, Lim Hai Bi, Loh Wan Jing, Alan OwYong, Ho Hua Chew, Lim Kim Keang, Gerard Francis, Con Foley, Lau Jia Seng, Han Chong, See Swee Leng, Jimmy Chew, K.S. Wong.
Reference: Ho, H. C. & OwYong, A. 2015. Report on the Shorebird Monitoring Project at the Sungei Buloh-Mandai Mudflat Coastal Sector: 28 November 2011 – 18 September 2012. Singapore: Bird Group, The Nature Society. Unpublished.