What social behavior is exhibited by these birds during the late summer and fall periods?

Answer

They gather into very large, communal roosts, sometimes reaching up to 1,000 birds.

In contrast to the breeding season when they forage alone or in pairs, in late summer and fall, they congregate into massive communal roosts.

What social behavior is exhibited by these birds during the late summer and fall periods?
dietbirdinsectwildlifeFlycatcher