At a Glance

Some 120,000 pink flamingos were counted in Mumbai in January.Typically, between 30,000 and 40,000 of the birds migrate to the city every year.Drought and declining habitat could also be to blame for this year's mass migration.

Flamingos are flocking to Mumbai in record numbers this year and, in what may be an environmental double sword, some experts believe raw sewage and industrial pollution are the reason why.

Between flamingos typically migrate to India’s largest city each year, but a count in January tallied 120,000 of the iconic pink guards, the Guardian newspaper reported.

They can be seen flying in huge flocks, skimming the waters of Mumbai’s Thane Creek inlet, where tour boats take locals and visitors on cruises to view flamingos, as well as the other 200 species of birds that live on the waterway.

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"The scene in the when they are wading in the water is amazing," Rahul Khot, assistant director of the Bombay Natural History Society, told National Public Radio’s Weekend Edition.

The inlet’s waters are a murky green due to algae that is fed by increasingly higher sewer discharges from a nearby water treatment plant, as well as industrial run-off.

“It is a well-studied phenomenon in nature that one species’ waste is food for the other,” Debi Goenka, BNHS honorary secretary, told the Guardian. “The sewage in the creek promotes biological growth of blue-green algae, which is food for the flamingo.”

Sunjoy Monga, a naturalist and author of the book Birds of Mumbai, also told the Guardian the creek may have reached “what one might call perfect levels of pollution,” due in part to increasing water temperatures.

“Over the years the industrial discharge dispelled by the industries of the Sewri Bay may have warmed the water,” Monga said. “The nitrate and phosphate levels in the creek water are just right for the prolific growth of the algae.”

With a population of 18 million, to handle wastewater and increasing pollution in its many urban waterways, which serve as important fishing grounds for local villagers and as transportation routes around the region. A 2016 report in the Times of India said had reached alarming levels, and people who came in contact with the water were breaking out in rashes.

Other environmental factors could also be at play. Monga speculates that “drought-like conditions” in other parts of India are the specific reason the flamingos have migrated to Mumbai in such large numbers, according to the Guardian, while other experts believe declining habitats may be to blame.

There are of flamingos in the world, and none of them are currently endangered. Mumbai's are greater flamingos, which is the largest and most adaptive to different habitats. The birds migrate to Mumbai from the northwest regions of Kutch in Gujarat and Sambhar Lake in Rajasthan, according to the Guardian. Smaller numbers of the birds are believed to fly in from Pakistan, Afghanistan, Iran and Israel, while still others are thought to come from as far as France.

Khot told NPR he and his team aren't convinced quite yet that the sewage output and industrial runoff are specifically what attracted the flamingos, but they welcome the spotlight on their pink feathered friends and hope the attention will help conserve their habitat for future generations.