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Mystery Migration: Common Birds Vanish, Then Return
20 Nov
Summary
- Pond herons and cattle egrets disappear annually from mid-June to September.
- Birds undertake organized night flights, observed in flocks moving south.
- Seasonal travel linked to water availability and agricultural cycles.
A curious annual phenomenon is unfolding along India's east coast, where familiar pond herons and cattle egrets vanish for nearly four months each year. First observed in the late 1980s, these birds disappear from wetlands between mid-June and September, only to reappear in mid-October, undertaking determined night flights southward. This long-observed pattern has recently gained traction with coordinated citizen-science efforts, documenting these movements across regions like Visakhapatnam.
The seasonal relocation, involving both modest groups of pond herons and larger, coordinated flocks of cattle egrets, suggests a deliberate, planned journey. Initial observations point to a general southwestward direction. While the exact destinations remain under study, possibilities include the Rameswaram coast and potentially Sri Lanka, with temporary stops at intermediate wetlands.
Experts believe this enigmatic behavior is tied to environmental shifts. Declining water levels during the dry months likely reduce food availability, compelling the birds to seek more hospitable locations. Parallel theories suggest a link to agricultural cycles, with birds appearing when paddy fields provide ample prey and departing after harvests when foraging becomes difficult.
