Fig. 3
From: Songbirds initiate migratory flights synchronously relative to civil dusk
Nocturnal departure time from wintering (beige) and breeding sites (blue) in relation to sunset (top) and civil dusk (bottom) for species likely initiating long-distance migratory flights at departure. Notice the smaller difference between Gambel’s White-crowned Sparrow and all other species when using time after civil dusk compared to time after sunset. Quebec-breeding Swainson’s Thrush and Gambel’s White-crowned Sparrow are shown here with species likely initiating migratory flights because their distributions of departure times are similar, but we do not have post-departure detection data to confirm that they were beginning migration (see Methods)