Sanderlings Feeding & Rhynchokinesis – Thailand Birding


A few days ago I visited Pranburi Forest Park in Prachuab Kiri Khan province for a few hours in the afternoon. There was not a lot to be seen in the mangroves and the coastal woodland, just a single Forest Wagtail, some Malaysian Pied Fantails, an Indian Roller and a few Golden-bellied Gerygones. However, on the beach there were up to 100 shorebirds, most of which were Lesser Sand Plovers with a smaller number of Pacific Golden Plovers, 4 Malaysian Plovers and around 10 Sanderling. I sat down close to where they were feeding and waited and after a short time many of these birds came quite close to me as they fed. It was particularly interesting to watch the Sanderlings feeding and the following are some photos showing their feeding behaviour including an example of “rhynchokenesis”.

In these first two photos the foraging behaviour of Sanderling can be seen. I noticed that they would plough a short furrow in the sand using their upper mandible into which they would probe with the tip of their bill.

sanderling5Sanderling feeding by Nick Upton

sanderling4Sanderling feeding by Nick Upton

In this next photograph this bird has just swallowed a food item. I did not get any good photos of what they were eating but they seemed to be small, round objects. Possibly crab eggs or something similar?

sanderling6Sanderling swallowing food by Nick Upton

This feeding action often left the birds with little dollops of sand on their upper mandibles as can be seen in the following photograph. In fact it was tricky getting a picture of one without this sandy addition to their bill.

sanderling7Sanderling after feeding by Nick Upton

Perhaps the most interesting thing I noticed, after looking at the photographs, was that as they fed the Sanderlings sometimes flexed their upper mandibles upwards. This behaviour is known as rhynchokenesis and is well-known in Snipe and I have also seen Broad-billed Sandpiper performing some amazing bill contortions too.

sanderling3Sanderling flexing its upper mandible upwards by Nick Upton

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