Figure 1

Actograms (a, b) and migration routes (c) of European Nightjars breeding in Belgium (a) and in Mongolia (b). Example of actograms from two individuals showing daily activity (red = migratory flight, blue = foraging activity, white = no/low activity, measured per five-min period) covering migration segments (Belgian individual: B1-3, Mongolian individual: M1-4) from dusk until dawn. Each horizontal bar shows one day with time on the X-axis. Time is plotted in eight-hour intervals and centred around local midnight. Black lines show the timing of sunset at the estimated location of each individual. Stopover periods are not shown on the actograms. The bottom map (c) shows the categorized biomes [barriers (red), hospitable (green); adapted from³⁷] with geolocator tracks (dotted lines) and GPS-tracks (full lines). White dotted lines show the migration routes of one Belgian individual (represented in actogram a) and one Mongolian individual (represented in actogram b). White stars indicate stopover areas (> 3 days), blue diamonds represent breeding areas and yellow circles represent wintering areas.