Society

Eurasian Oystercatcher: Let the beak do the talking

Eurasian Oystercatcher feeding around a mudflat in Pulicat. Photo: Rama Neelamegam   

The twenty-first century family is divided at the dining table, parents separated from children by the contents of their individual Swiggy orders.

Eat your hearts out, human parents! Your Eurasian-Oystercatcher (Haematopus ostralegus) counterparts are on vastly better gastronomic ground, being better placed to influence their progeny in not only what they feed on — but also how they feed on it.

On the Chennai coast, this side of the Eurasian Oystercatcher would remain unseen, as the bird is a migrant in these parts.

Knowing how someone is around home, is to really know them. So it is with birds. And therefore, read on.

Under the blinding glare of research for long, the Eurasian Oysterctacher’s feeding behaviour has thrown up studies as wide-ranging as the wingspan of the Wandering Albatross.

Is it a dwindling species?
  • The Eurasian Oystercatcher is a near-threatened species, a fact that should be obvious to anyone tracking the species over the last four decades — in their breeding or wintering grounds.
  • From the 1980s — when he was a habitue of the Gulf of Mannar, on account of his doctoral work — to now, S. Balachandran, deputy director, BNHS Regional Migration Study Centre at Point Calimere has noticed the species is on a downward spiral.
  • The contrast between then and now is nowhere as stark as in this region.
  • “Earlier, 20 to 30 birds would come regularly to Gulf of Mannar during the migratory season — from 1980s to 2000s, the bird would be seen regularly. But the numbers were dropping steadily, and now the bird seems to be completely absent in Gulf of Mannar. That has been the experience for the last seven years,” says Balachandran.
  • Even in the best of times, the species would arrive in trickles in its wintering grounds on the East Coast.
  • “It was earlier seen regularly in small numbers, with the maximum numbers coming from Rameswaram, more precisely around some of the islands near Rameswaram. From their numbers being registered now, the species seems to be dwindling. At Point Calimere and Pulicat, there are occasional sightings of one or two Eurasian Oystercatchers,” elaborates Balachandran.
  • From its name, the bird’s preference for oysters is evident. However, the bird also has a taste for other bivalve molluscs.
  • “Around Point Calimere, there is not much of oysters to be found. During the monsoon, other bivalve molluscs are moved ashore. During that time, the Eurasian Oystercatcher may come in numbers of three or four — that has been my experience this year too. At Point Calimere, at the sea mouth, one tends to see two or three of them.”

Recently, ornithologist V. Santharam encouraged this writer to get his beak into some of these studies. What the Rishi Valley-based ornithologist did next virtually sealed all avenues to procrastination: He promptly forwarded links to not one, but three of them.

The one that was pecked at — the 1968 study “The feeding behaviour of the oystercatcher, Haematopus ostralegus” by M. Norton-Griffiths under University of Oxford — is an acclaimed work.

Just from the abstract, there are these takeaways.

One, effective feeding is a result of sustained parental coaching — in Chennai, the resident, breeding Purple Moorhen and Bronze-winged Jacana (the male of this species) are among birds that will demonstrate this idea to some extent. It is the level of coaching that puts the Eurasian Oystercather ahead of most other winged parents.

Eurasian Oystercatcher parents that had signed up for Norton-Griffiths’ study showed how they drew up a mental time-chart of when their young should be allowed to go solo on a particular kind of prey.

Norton-Griffiths noticed that around “6-7 weeks”, the parents trusted the young ones to be adept at “probing for worms”. Where making a meal of “molluscs and crustacea” was concerned, the parents wound up the training programme anywhere between 12 and 20 weeks. For the young slow on the uptake, this training sometimes went up to a patience-draining 43 weeks, the study notes.

The techniques employed by Oystercatchers to tear into their prey are discussed, with Norton-Griffiths particularly elaborating on a five-pointed reportoire: Namely, “stab, hammering, levering, prising and chiselling”. With so many ‘fork-using techniques’ in its quiver, the Eurasian Oystercatcher is bound to remind one of the Ruddy Turnstone.

Norton-Griffiths found that the young Oystercatchers proved adept only at those skills the parents themselves were past-masters at. The parents’ ability to impart these skills to the young also mattered.

Three locations

Now, off to the bird’s stomping grounds during migration, which includes patches of the Chennai coastline. Here, the Eurasian Oystercatcher can launch into bivalve molluscs, including those much-desired oysters, free of the pressure of having to prepare for a feeding-masterclass every day.

“The bird comes at certain times of the migration season, and is not found regularly around Chennai. It comes in small numbers and is found in very specific locations on the Chennai coast — that is how it used to be. At Pulicat, you might see it more often,” says Santharam, largely from his observation of the species at Adyar Estuary and Pulicat from the late 1970s to the early 1990s.

When this writer sought eBird reviewer Vikas Madhav Nagarajan’s view in the matter, one could hear the echo of the past. The species seems to have hardly veered away from the pattern if has always followed around Chennai. Vikas’ observation: “It is found in specific areas — Pulicat, Mudaliyarkuppam Backwaters and Adyar Estuary. It is recorded off and on at Adyar Estuary. Muttukadu in the Covelong area is where they may likely be found. With its mudflat habitat, Muttukadu has oysters to offer these birds.”

In small numbers

From his observations around the Adyar Estuary, Santharam points out that the river mouth is a good place to look for the Eurasian Oystercatcher.

“The species does not occur in the interiors, and is found very much on the coast, at river mouths. Between the late 1970s and early 1990s, at Adyar Estuary, I have seen the species several times,” says Santharam. “When I would visit Pulicat, I would head to the lake part, and not the mouth of the Pulicat lake, where I think there is a better chance of sigthing the bird.” In the 1990s, Santharam was carrying out bird-ringing with BNHS at Sriharikota.

S. Balachandran, deputy director, BNHS Regional Migration Study Centre, brings a similar observation from his stomping ground, Point Calimere, where the Centre is located.

“In Point Calimere, at the sea mouth, there is the possibility of seeing two or three Eurasian Oystercatchers, occasionally.”

Shantaram, considers the Eurasian Oystercatcher more of a passage migrant. “It comes in the autumn migration: It comes fairly early. It probably goes down south — to Sri Lanka, Rameswaram and the coastal areas around there.”

(Migrant Watch is a weekly column that discusses the birds visiting Chennai and its thereabouts during the migratory season)

This article is closed for comments.
Please Email the Editor

Printable version | May 14, 2021 9:10:28 AM | https://www.thehindu.com/society/eurasian-oystercatcher-let-the-beak-do-the-talking/article34343317.ece

Next Story