Lake dredging works leads to steep decline in bird population at Ooty lake

Ooty lake's wetland bird population declines due to human activities, impacting biodiversity and raising environmental concerns.

For the second consecutive year, human activities have caused a steep decline in the population of wetland birds utilising the Ooty lake, which in 2023, recorded the highest density of bird life in the Upper Nilgiris.

In 2023, Ooty lake accounted for 27 of the 35 wetland bird species spotted across 14 water bodies in the Nilgiris forest division, with 600 birds sighted during an exercise conducted as part of the state-wide wetland bird survey. The same exercise in 2024 revealed a drastic decline, with only 13 species and 270 birds being sighted. This year, the species diversity and density have fallen even lower due to an ongoing clean-up of the lake, that began late last year.

“The 2024 decline was caused by the construction of adventure facilities around the lake. However, the huge undertaking to clean the lake has resulted in an even more severe reduction in avian diversity and density,” said birdwatchers who have been documenting the water body’s importance to biodiversity over the last few years.

N. Moinudheen, an independent wildlife researcher, said that more birds were spotted prior to the clean-up, including pintails, ducks, coots, moorhens and waterhens. “The birds that utilise the lake are highly susceptible to human disturbances, and the dredging of the Ooty lake is the main reason for the decline in the number of birds,” said Mr. Moinudheen, adding that the peripheries of the lake, where the clean-up is most active, also serve as feeding grounds for the birds.

Meanwhile, the pumping of the water from the lake into the surrounding wetland, which many of the birds use as nesting sites, has raised concerns among environmentalists about the potential damage to the biodiversity.

Godwin Vasanth Bosco, a restoration ecologist from the Nilgiris, said that the wetland surrounding the lake was already in a “disturbed state.” He warned that that eutrophication and algal growth caused by the pumping of the highly-polluted water was a concern. “As the water in the lake is already polluted from sewage and agricultural run-off, nitrogen pollution is also a concern,” said Mr. Bosco.

When contacted, S. Gowtham, Divisional Forest Officer (Nilgiris division), said that the Forest Department did notice a steep decline in the bird population in the lake, but would bounce back once the clean-up and dredging works are complete.