Mumbai Local

Why Sewri mudflats attract flamingoes remains a mystery

The birds arrive in the city from Kutch in Gujarat by mid-November—Photo: Vivek Bendre  

From the moment they first arrived in Mumbai in the mid-1990s, flamingoes have kept their date with the city every winter. Despite their annual sojourn making them a major attraction among birdwatchers and researchers, the reason why these migratory birds prefer the marshes at Sewri remains a mystery.

The birds are said to share a “passive symbiotic” relationship with the mangroves, which serve as food and shelter for the birds. In turn, the excrement of the birds could help in the growth of the mangroves.

“One reason could be eutrophication (a natural process in lakes which enriches the ecosystem) that helps in the formation of blue algae that they feed on,” says Asif Khan, bird expert at the Bombay Natural History Society. “The shape of the bay area surrounded by mangroves could also be a possible reason. However, the reasons why they prefer Sewri are not conclusively known.”

The mudflats are a rich feeding ground for the flamingoes who arrive from Kutch. The area also supports a large number of birds including stints, grey herons, black-headed ibis, sandpipers, plovers and egrets, who feed on a variety of marine life comprising fiddler crabs, fish and small invertebrates.

“When the tide is low and the mudflat is open, they feed on the mudflats,” says Mr Khan. “During high tide, they roost in internal wetlands. Ponds near TS Chanakya and the NRI Complex on Palm Beach Road in Navi Mumbai are such roosting ponds. In Maharashtra, the Sewri mudflats possibly sees the largest congregation of Lesser Flamingoes at a single spot.”

Since their first visit, flamingo numbers have grown; the numbers seem to be stable for the last couple of years. Last year, about 20,000 birds were recorded at Sewri. This winter, about 10,000 have been recorded so far. The number is expected to swell and touch its peak by February end.

The flamingoes shift between the feeding grounds of Sewri and Airoli in Navi Mumbai, some also making their way to the Thane creek. By May end the birds start leaving for Kutch and by the first week of June, the last batch leaves.

“This year the flamingoes arrived late. They usually come by mid-November, but this year they came in December owing to a good rainfall in Kutch, which is among the four or five flamingoes known breeding grounds for the Lesser Flamingo in the world. The others are in South Africa, and East Africa. We are still to see the Greater Flamingoes. So far only the Lesser Flamingoes [smaller in size] have been spotted at Sewri,” says Mr Khan.

On Saturday morning, eager Mumbaikars, who signed up for the BNHS’ ‘Flamingo Watch’ gathered near the Sewri station. A short walk through dusty lanes led to the pathway of the marshy bay. Beyond a row of jetties, flocks of the pink wading bird were seen dunking their heads in the water to take in the food and making the most of the low tide. A vast expanse of mangroves — a restricted area — stretches beyond their lines.

Along the shore, a ship is being broken with gas cutters. Parts of ships and other debris are floating near the shore. Flamingoes feed on polluted waters, which produce the blue algae.

The impact on the birds of heavy metals in the water is yet unknown, but not too difficult to predict.

“Humans are the biggest threat to the flamingoes,” says Mr Khan.



Experts say the blue algae, which the flamingoes feed on, could be a possible reason



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Printable version | Mar 7, 2021 11:49:49 PM | https://www.thehindu.com/news/cities/mumbai/news/Why-Sewri-mudflats-attract-flamingoes-remains-a-mystery/article14005066.ece

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