Asian Openbill – feeding technique

“Large numbers of migrants Asian Openbill (Anastomus oscitans) again this year (see last year’s visit HERE and HERE.

“I saw in excess of 110 in a single flock. Managed to get close to watch the feeding behaviour, see the composite image (above). They are very adept at getting at the soft body of the freshwater Golden Apple Snail (Pomacea canaliculata) without damaging the shell.

“I believe this was first described by Kahl M.P. 1971. Food and feeding behavior of openbill storks. Journal of Ornithology, 112: 21-35, who said: ‘The usual method of extracting the molluscan body from the shell is described. Most commonly the tip of the lower mandible is inserted into the shell and the body dislodged, without great damage being done to the shell. The popular notion that the open bill functions in the fashion of a “nutcracker” is not supported by my observations. It is suggested that the major adaptive advantage of the open bill is that it gives the birdconvergent mandible tips, which assist in the grasping and carrying of molluscs as well as their extraction.’

“In a recent publication Sawangproh W., Round P, Poonswad P. 2012. Asian openbill stork Anastomus oscitans as a predator of the invasive alien gastropod Pomacea canaliculata in Thailand. Iberus, 30 (1): 111-117, they stated ‘We observed that storks searching for snails probed with their bills under and adjacent to floating vegetation and rice stalks. The stork slightly opened its bill and stabbed through the water. When a snail was located, the stork quickly closed its bill, pinned the snail to the ground with its mandibles and then pushed the tip of the lower mandible in to open snail operculum. Once the operculum was opened, the stork then inserted its mandibles, lifted up the snail, shook its bill to free the snail’s body from its shell, swallowed the flesh and discarded the shell and operculum.’

“My close up observations of feeding agree with these (above 3 images).”

Dato’ Dr Amar-Singh HSS
Ipoh, Perak, Malaysia
2nd February 2013

Location: Ulu Dedap, Perak, Malaysia
Habitat: Extensive rice farming area, wetlands with nearby rivers

2 Responses

  1. I recently spotted a stork-like bird while birdwatching at the Kallang Riverside. It was large, had a stork like neck and beak and was almost completely white except underwing the colours were split black and white. The tail also had some black feathers. Can anyone identify which type of stork this would be?

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