During the month of February 2025, the Singapore birding community was in high excitement again as big flocks of Asian Openbill Storks, Anastomus oscitans were seen in various locations around Singapore. They are native to the Indian continent and parts of Burma, Thailand, Laos and Cambodia. Some birds do visit parts of the Malay Peninsula. Read this account by Lena Chow https://besgroup.org/2013/01/30/asian-openbills-at-batang-tiga-malacca-malaysia/ about the birds being sighted at Batang Tiga, Malacca in January 2013. A few days later the birds were also seen for the first time in Singapore. Read the account here https://besgroup.org/2013/01/29/asian-openbill-migrating-south/ . Many of these visitors are young birds as evidenced by their brownish head plumage.
On 23 December 2019, large numbers of them visited Singapore again. View this video by the Straits Times https://www.youtube.com/watch?v=8m4OY26cLMI . Since then, small numbers of 1-3 birds have been sighted. According to figures published in Birds of Singapore, the period 12 March 2024 – 6 April 2024 an estimated 220 birds and the period 23 Jan 2025 – 22 March 2025 an estimated 300 birds visited Singapore again. https://singaporebirds.com/species/asian-openbill/
I visited Kluang, Johor, Malaysia and spotted two Asian Openbills fishing in Sungei Mengkibol on 8 March 2025. They looked like young adults[2].
One was hanging out with a Little Egret, Egretta garzetta, the one with the long black legs with yellow feet: and black beak. The two birds often moved along the river in close proximity to each other. Sometimes the Little Heron, Butorides striata walks over to join them. Non-breeding openbills seldom display intra- and interspecific aggression[2].
While scanning the river bank opposite I noticed another openbill standing very still on the riverbank. It was well-camouflaged and remained in that position for a couple of hours. The feathers on its head were damp. Taking a breather from feeding and staying out of sight?
Throughout my visit, I only noticed one openbill feeding actively in the river.
Video 1 by K Wong. Kluang, Johor, Malaysia. 11 March 2025 The openbill grips the snail and steadies it against the underwater sandy riverbed. The depth of the water necessitates it to put its head under water to do some underwater manipulation before bringing the snail up. Its nictitating eye membranes protect its eyes from the running river water, enabling it to see well while underwater. The manipulations involve inserting the tip of its razor sharp lower beak under the snails operculum, and then cutting away the muscle attachment to the columella, freeing the soft flesh from the hard shell. It then brings the whole complex up to the surface of the river, where with a simple shake, the flowing water separates the shell from the flesh. The river washes the hard shell away and the bird gobbles up its tasty meal, all within less than a minute.
In this article https://lkcnhm.nus.edu.sg/wp-content/uploads/sites/11/app/uploads/2017/06/2013nis135-141.pdf the authors S.K. Tan, Y.L. Lee and T.H. Ng described the distribution of Pila scutata in the surrounding region and Singapore. They are also described as small, growing to 50 mm. The eggs are laid in small white clusters.
https://www.fws.gov/sites/default/files/documents/Ecological-Risk-Screening-Summary-Pila-scutata-snail.pdf describes Pila scutata as native apple snails in Malaysia too, small in size and having black shells.
I did not notice any pink egg clusters (point to golden apple snails, Pomaceae canaliculata) in Sungei Mengkibol and conclude that any white egg clusters of Pila scutata if present may not have been visible against the algae-covered rock and cement surfaces of the river banks. The snails that the openbills fed on were mainly picked up amongst vegetation overhanging the water edge, black, relatively small and could be the local apple snails. The openbill would have preferred them.
Amar Singh HSS wrote about openbills feeding on the introduced apple snails Pomaceae canaliculata https://besgroup.org/2014/03/16/asian-openbill-feeding-technique/ and other prey https://besgroup.org/2014/08/30/asian-openbill-other-prey-consumed/ . I guess that this openbill was feeding on the Pila scutata. I will examine the snails at close range on my next trip to Kluang if the river is not swollen with rain.
In the video above, the openbill uses its upper bill to steady the bivalve against the ground, inserts the lower bill in between the shells and moves the lower bill in an action similar to us using a knife. The two shells are soon separated and the bird grabs the flesh, shakes it vigorously to dislodge the shells, and gobbles its prize in a jiffy.
The birds’ specially evolved bills are equally adept at handling molluscs with one and two shells. Videos 1 and 2 support what Weerachon Sawangproh[1] of Mahidol University, Thailand observed about the amount of damage to the shells of large and small snails.
References:
- https://mahidol.elsevierpure.com/en/publications/notes-on-the-foraging-and-feeding-behaviours-of-the-asian-openbil
- Handbook of the Birds of the World © 1996 Vol. 1
