Extended Data Fig. 8: Spatial positions of birds at movement onset differ between call-accompanied and call-unaccompanied upwards movements.
a,b, Spatial positions of calling birds (light green) and their flock mates (light blue) at the onset of call-accompanied upwards movements, and spatial positions of all birds at all time steps of four entire flocking flight sessions (light grey). Dark blue, dark green and dark grey lines indicate the interquartile ranges of horizontal and vertical positions, and of horizontal and wind direction positions of calling birds at call onset, their flock mates at call onset and all birds during four flocking flight sessions, respectively. The lines’ intersections are at the medians of the distributions. c,d, Spatial positions of upwards moving birds (light orange) and their flock mates (light cyan) at the onset of call-unaccompanied upwards movements, and spatial positions of all birds at all time steps of four entire flocking flight sessions (light grey). Dark orange, dark cyan and dark grey lines indicate the interquartile ranges of horizontal and vertical positions, and of horizontal and wind direction positions of moving birds at movement onset, their flock mates at movement onset and all birds during four flight sessions, respectively. The lines’ intersections are at the medians of the distributions. Thin black lines represent the flight section’s outline. At the onset of both call accompanied (a and b; n = 46, 13 flight sessions) and call unaccompanied (c and d; n = 579, one flight session) upwards movements, the bird that moved upwards was located at significantly (LMM, estimates ± SE: 103.4 ± 22.3, p < 0.001, t = 4.65, for call-accompanied movements, and estimates ± SE: 13.0 ± 6.3, p = 0.04, t = 2.05 for call-unaccompanied movements) lower spatial positions than any bird was located throughout the flight sessions (n = 43,927 (four sessions) and n = 10,524 (one session) for call-accompanied and call-unaccompanied movements, respectively.
