COIMBATORE: A second wave of butterfly migration has been recorded across the western districts of Tamil Nadu, following an earlier movement in mid-September. Large numbers of four species from the Danainae subfamily, Blue Tiger (Tirumala limniace), Dark Blue Tiger (Tirumala septentrionis), Common Crow (Euploea core) and Double-branded Crow (Euploea sylvester), have been spotted across the region.
The current wave, which is larger than the first, gained momentum following fresh northeast monsoon rains and the withdrawal of the southwest monsoon in mid-October. The movement has been recorded in Salem, Namakkal, Erode, Tiruppur and Coimbatore districts, according to members of the Nature and Butterfly Society (TNBS).
“Blue Tigers were recorded passing through Rasipuram at a rate of 72 per minute by one of our members, with large numbers heading towards the foothills of the Western Ghats. The westward and south-westward movement is consistent with the pattern expected during the onset of the northeast monsoon. A reverse migration from the Western Ghats towards the plains would generally begin in April or May the following year,” said A Pavendhan, president of TNBS. Members of the Coimbatore Nature Society also assisted TNBS members in observing the migration in Coimbatore district.
The migration peaked over the weekend, with sightings reported across Coimbatore district, from Mettupalayam to Singanallur, between 8.30 am and 4 pm on Saturday (October 17). The rate of movement ranged from five to 135 butterflies per minute. Sightings of migrating Crows and Tigers continued on Sunday (October 18) in Erode and Tiruppur districts, including Udumalpet.
“Moderate rainfall was recorded across Tamil Nadu during this period, particularly along the migration corridor. However, one unusual observation was that the butterflies were flying much closer to the ground than usual. While they are typically seen migrating at heights of five to 25 metres or more, their lower flight path this time warrants further ecological study,” said K Sadhees Kumar, a senior TNBS member from Erode district.
The low-flying movement has also resulted in butterfly deaths on busy roads, said S Gopalakrishnan, another senior TNBS member. “Several instances of roadkill were reported as the butterflies crossed busy traffic. In one instance, more than 1,000 specimens were reportedly killed. Upon reaching the foothills of the Western Ghats, the butterflies were seen congregating on nectar-bearing plants,” he said.