Ron Alsop

Purple martins, members of the swallow family, are native songbirds. East of the Rocky Mountains, they now rely entirely on human-provided housing. In late summer, they gather in massive flocks — called migratory roosts — to rest, socialize, and eat before migrating to South America. With a little creative thinking, you can attend a martin roost and witness something unforgettable. I’ve had the pleasure twice, in two different states. One trip was completely spontaneous; the other took me to Texas.