Sunset and the orientation of a nocturnal bird migrant: A mirror experiment

Summary If savannah sparrows, (Passerculus sandwichensis), a North American night migrant, select a migratory heading based upon the setting sun, a shift in the position of that cue should produce a predictable shift in the migrant's nocturnal orientation. I tested this hypothesis by shifting the sunst position with mirrors and by recording the bird's orientation in Emlen funnels. The control group displayed directionality appropriate for spring migration (=342°). The mean heading of experimentals (=272°), which were exposed to a cue-shifted situation, was in the expected westerly direction relative to the control mean (P<0.05, V-test). The setting sun appears to be a sufficient source of directional information for this avian migrant.