Fig. 4

Simulated autumn and spring migration routes of northern wheatears migrating breeding in Alaska. Migration routes are shown between the breeding sites in Alaska and the wintering areas in eastern Africa in comparison to the actual routes taken by the individual birds as estimated from geolocator information [see 32 for details on tracks]. Illustrated are the rhumbline routes (black), time-compensated sunset compass routes (green), fixed (menotactic) sunset compass routes (blue), fixed (menotactic) magnetic compass routes (red), and magnetoclinic compass routes (orange). The exact great circle routes (dark grey dashed) are shown for comparison. Initial departure locations are indicated as black triangles and destinations as black dots. Green dots indicate locations where the compass courses were reset. Dotted sections of time-compensated sunset compass routes indicate locations where the sun did not set below the horizon, thus where the birds had to use the lowest sun elevation as sunset. Dotted sections of magnetoclinic compass routes indicate locations where the angle of inclination of the Earth’s magnetic field was larger than the apparent angle of inclination. Estimates of locations, incl. 95% credible intervals are given in yellow to green shades (see [32] for details). All maps are in Mercator projection. For further information see Table 2 and main text