Fig. 3: Vocal activity during flight depends on social context.
a, Calling activity differs between flocking and solo flight sessions. Histogram bin size: 2 ms. Red lines: duration of flight sessions. n = 308 calls emitted by 5 birds in 13 flocking flight sessions and n = 22 calls emitted by 1 bird in 19 solo flight sessions. b, Spectrogram (fast Fourier transform length: 512, 99.6% overlap, Hamming window) of a stack call emitted by bird Green during flocking flight. Light colours represent high energy. c,d, When emitting a stack call during flight, the calling bird (n = 93; light green dots) was positioned at a significantly (LMM, estimates ± s.e.m.: 252.3 ± 49.9, P < 0.001, t = 5.06) lower, significantly (LMM, estimates ± s.e.m.: 154.6 ± 74.3, P = 0.038, t = 2.08) more right (c) and significantly (LMM, estimates ± s.e.m.: 564.8 ± 97.2, P < 0.001, t = 5.81) further upwind (d) position than its flock mates (n = 465; light blue dots). Grey dots: all positions of all birds during four flight sessions; dark blue, dark green and dark grey lines: IQRs 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 flight sessions, respectively; the lines’ intersections are at the medians of the distributions; thin black lines: flight section’s outline.
