Butterfly Migration in Tamil Nadu: Below-Par Phenomenon Raises Concerns

November 28, 2023

The mesmerizing annual migration of butterflies from the Eastern Ghats towards the Western Ghats in Tamil Nadu, coinciding with the onset of the Northeast monsoon, witnessed a subpar occurrence this year. Tracking this phenomenon since 2013, The Nature and Butterfly Society (TNBS) observers noted a deviation from the usual large-scale movement, attributing it to below-normal rainfall in the west zone districts.

Origins of Migration

The Eastern Ghats complex, including the Yercaud hills, Pachamalai, Kolli hills, and Kalvarayan hills, serves as the major starting point for butterfly migration in Tamil Nadu. Before the Northeast monsoon sets in, butterflies from the subfamily Danainae, such as Blue Tiger, Dark Blue Tiger, Double-branded Crow, and Common Crow (collectively known as ‘Tigers and Crows’), embark on a journey westward. However, this year, observers noted only a limited migration of these species since September.

Rainfall Discrepancy

TNBS reports that Tamil Nadu experienced 92% of its normal rainfall from June to September 2023. However, districts crucial for migratory movement in the west zone, particularly Salem and Namakkal, faced rainfall deficits of 7% and 10%. TNBS member A. Pavendhan suggests that optimal migratory movement is observed during periods of excess rainfall, possibly contributing to the subdued migration this year.

Impact on Regular Routes

Many well-established migratory routes, usually bustling with butterfly activity, remained dormant this season. Out of the usual 15 migratory routes in Coimbatore district, only a handful showed any movement. Notable butterfly congregations were observed in specific locations like Ponnuthu hills, Kallar, and Anaikatti.

Climate and Migration Dynamics

Observers highlight the intricate relationship between climatic conditions and butterfly migration, pointing to a potential correlation between rainfall and migration patterns. TNBS has collaborated with ‘Butterfly Migration India,’ a portal aggregating information from all states, to deepen the understanding of this phenomenon.

Local Albatross Movement

While the migratory spectacle saw a dip, observers noted a noteworthy local movement of Common Albatross butterflies in large numbers. This species, belonging to the Pieridae family, showcased vibrant activity from the low to mid-elevation hills of Anaikatti and the Nilgiris, heading towards the Sirumugai forest range and Sathyamangalam Tiger Reserve in the second week of November.

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