On quiet nights in spring, if we stand outdoors and listen, we may hear the nocturnal flight calls of migratory songbirds drifting down from overhead. Especially in late May in eastern North America, one of the most characteristic sounds is the soft, bell-like whistle of Swainson’s Thrush. During a major flight we might hear dozens of them per hour, but the next morning it will take some work to find a fraction of those numbers: After landing at dawn, the shy brown thrushes seem to melt away into the thickets.
Identifying brown thrushes in migration is an annual challenge for birdwatchers. Swainson’s Thrush occurs throughout most of North America as a migrant, and it’s widespread in the North and West in summer, so observers everywhere have reason to study its ID points.