Large yearly fluctuations in congregation sizes of migratory Danainae butterflies in the Western Ghats, India

We documented the overwintering congregations of migratory Danainae
butterflies (Nymphalidae) over six migratory seasons in the threatened
tropical forests of the Western Ghats, India. Congregation sizes
fluctuated drastically (>90%), indicating vulnerability to chance
events. Continued monitoring is needed to explain these fluctuations and
identify declining trends for timely conservation action.