THOOTHUKUDI: As we commemorate the World Migratory Bird Day on May 14, let us check out our winged visitors' grim state of affairs in the grasslands of the southern states. Researchers say the number of migratory birds such as harriers is on the decline due to the expansion of developmental projects and industries in Thoothukudi and Tirunelveli. The aggressive rise of windmill projects in the semi-arid regions between Kayathar and Aralvaimozhi has dealt a severe blow to the grasslands' biodiversity, they say.
The vast expanse of semi-arid land in both the districts is a habitat for hundreds of animal species, including snakes, Indian small fox, mongoose, different kinds of rodents, and over 80 bird species. Lindernia minima, a new plant species, was discovered here recently. The endangered Madras hedgehogs are also found in this landscape in large numbers. Harriers, a winter migratory bird, reach the Thamirabarani region by the end of September all the way from Central Asia and Russia, and leave by March. Montagu’s harrier (circus pygargus), pallid harrier (circus macrourus) and Eurasian marsh harrier (circus aeruginosus) are extensively found in the grasslands and shrublands of Tirunelveli and Thoothukudi, where they forage and roost during the winter.
"This migratory raptor bird mills over its prey before catching them. It mainly feeds on grasshoppers and also on other insects, rodents, small birds and some reptiles. Interestingly, the harriers follow communal roosting on the ground, with at least five individuals and a maximum of 75 in a cluster," Vinod, a birder, told TNIE.
A Saravanan, a research associate at the Ashoka Trust for Research in Ecology and the Environment, has been researching the characteristics of harriers since 2015. "The major clusters of harriers involve grasslands of Vagaikulam-Vallanadu in Thoothukudi, Moolakaraipatti and Radhapuram in Tirunelveli district. A new species of pied harrier (circus melanoleucos) was found at Vagaikulam in Thoothukudi, and Radhapuram and Moolakaraipatti in Tirunelveli during a survey in 2021," Saravanan said.
Harriers in the region are under threat due to various anthropogenic disturbances such as canal construction, intensive agriculture and urbanisation. According to an ongoing study, there is a declining trend in the arrival of harriers. The species population was 398 in 2015-16, 276 in 2016-17, 387 in 2017-18, 198 in 2018-19, 212 in 2019-20, 217 in 2020-21 and 201 in 2021-22, said Saravanan.
Senior Research Associate M Mathivanan attributed the decline to the expanding windmills and solar power projects in the semi-arid regions as a part of promoting renewable energy. Predatory birds such as eagle, vulture, kite and the migratory harrier mill in the sky over their prey at a certain height before they take the plunge. However, the windmill turbines severely obstruct this preying practice and also the birds' roosting, he observed.
Researchers had also observed an increasing population of prey species at the grasslands surrounding wind turbines, due to the absence of raptors there, he said further.
Another researcher Aditya Ganesh told TNIE that he had observed that harriers avoid roosting close to the windmill farms due to a variety of factors. The predation rate had declined near windmill farms, citing the increased population of the prey species, he said.
Vinod observed that harriers were being attacked by resident brahminy kites when the former shift their roosting site into the region dominated the latter. Windmill farms are being upgraded to higher altitudes without any proper impact assessment, said Aditya, and expressed concerns that research studies about the impact of the windmill farms are inadequate in south Tamil Nadu, which has the country's oldest wind farms.
The southern districts of Tamil Nadu are one of the largest windmill hubs in the country, contributing to at least 25% of India’s total installed wind energy capacity of 40 gigawatts (GW). Though green energy technologies like solar panels and windmills should be promoted, people must also realise that these technologies are not eco-friendly in terms of this region's biodiversity, Mathivanan concluded.