Mumbai’s Sewri mudflats see fewer birds; can’t blame trans-harbour link work yet, say experts

The number of birds at the city’s Sewri mudflats witnessed a significant decline between October 2019 and February 2020, compared to the corresponding period last year, according to a report by the Bombay Natural History Society (BNHS).

Flamingo numbers at the 500-hectare Sewri mudflat were 13,813 in January 2019 and 60,733 in March 2019, which fell to 4,395 in January 2020 and 4,106 in March 2020.(BNHS report ‘Monitoring and Mitigating impacts of the MTHL on flamingos and other avifauna’)

The area is witnessing construction of the Mumbai Trans-Harbour Link (MTHL) – a 21.8-km bridge connecting Sewri in Mumbai to Nhava-Sheva in Uran – since April 2018. While researchers said it may have kept birds away from the site, the report does not conclude so, stating “the impact of the construction on birds, whether temporary or permanent, can be inferred only after five years of post-construction monitoring.”

The report, ‘Monitoring and Mitigating impacts of the MTHL on flamingos and other avifauna’, was submitted to the Mangrove Foundation of Maharashtra last week. BNHS said the fluctuations were attributed to several factors that influence migration such as breeding success, weather, and habitat degradation along the flyway as well as alternate foraging and roosting habitats. The research began under its 10-year bird monitoring programme across select wetlands in October 2018. Deepak Apte, principal investigator of the project and director, BNHS, said, “The present report is purely an annual update and does not reflect conclusive findings yet.”

Flamingo numbers at the 500-hectare Sewri mudflat were 13,813 in January 2019 and 60,733 in March 2019, which fell to 4,395 in January 2020 and 4,106 in March 2020. This year’s data included only 287 greater flamingos during March and none in January. It was 1,497 in March 2019. Similarly, for all other water birds at Sewri, the number dropped from a maximum of 17,331 birds during November 2018 and 15,365 in February 2019 to 1,053 in November 2019 and 8,305 during February 2020. Nhava-Sheva, on the other end of the eastern seafront, saw a maximum of 4,500 water birds and 1,500 flamingos during February and March this year. Data from last year was available only from May 2019 onwards when 986 birds were recorded.

“By contrast to other wetlands in the Mumbai Metropolitan Region (MMR), results showed that Sewri and Nhava-Sheva supported lower species richness and abundance of migratory and resident birds throughout the survey period,” read the report.

With movement of people and machinery, there will be disturbance due to noise till construction takes place, said Apte, adding, “These annual updates are helping us develop a conservation and systematic blueprint for the seascape.”

BNHS also published results of bird behavioural studies for 10 species across roosting, feeding and construction sites in MMR from October 2019 to March 2020. A decline in wader (migratory shorebirds like little stint, Black-tailed Godwit, curlew sandpiper, and common greenshank) numbers was observed at Sewri and Nhava-Sheva mudflats, while there were minimal or no observations of Pied avocet and Whimbrels. Birds most observed were lesser flamingos, common redshanks and lesser sand plovers.

“During the early migratory season, birds prefer the northern part of the Thane Creek, and later move south towards Vashi and Sewri, which is why birds were seen during February and March in Sewri last season,” said Rahul Khot, assistant director, BNHS.

According to mangrove cell researchers, post-monsoon rain and impact of Arabian Sea tropical cyclones during October-November 2019 disturbed the natural migratory pattern to MMR wetlands. “The numbers drastically increased from last week of March till the rains began. For Sewri, some adverse effects of construction cannot be ruled out, but reduction in numbers cannot just be associated with that,” said Virendra Tiwari, additional principal chief conservator of forest (mangrove cell).

Mumbai Metropolitan Region Development Authority (MMRDA) joint metropolitan commissioner BG Pawar said, “Efforts were taken to ensure bird population was not disturbed right from day one of the project. We have been extra cautious. We have not seen the report, but will consult our engineers about it.” MMRDA commissioner RA Rajeev refused to comment on the matter.