Monarch butterflies are on the move through Massachusetts as part of their annual fall migration, and residents may spot them along the coast through early October.
The butterflies travel southward from mid-August into the fall, often following natural “leading lines” such as river valleys, ridgelines, and the shoreline, according to Mass Audubon. While each monarch migrates independently, large congregations are often seen at the coast or at communal roosts on cool nights.
Migrants typically fly in a steady direction when winds are favorable. During unfavorable conditions, such as strong southwesterly winds, they can be found feeding on nectar or resting until the weather shifts.
Mass Audubon notes that monarchs sometimes gather in dramatic numbers. At Eastern Point in Gloucester, more than 2,000 were recorded in a single day on Sept. 13, 1994.