SI Movie 3: Visualisation of the storks’ GPS tracks together with the estimated movement of the air. from Synchronization, coordination and collective sensing during thermalling flight of freely migrating white storks
mediaposted on 06.02.2018 by Máté Nagy, Iain D. Couzin, Wolfgang Fiedler, Martin Wikelski, Andrea Flack
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Black curves show 10 s trajectories of each bird; the width of the path is smaller for earlier points. The moving dots indicate the velocity of the air in the thermal; they colour coding represents the vertical speed. The vertical component of the air velocity was estimated for a 5 x 5 x 4 m (x, y, z) sized grid using the average vertical speed of the individuals. While rising in thermals, storks sink in the air that rises around them at a faster speed. Sink rate during gliding has a peak value of 1.2 m/s, and defines a minimum sinking speed. We estimated the air's vertical speed to be 1.2 m/s larger than the vertical speed of the storks. The horizontal speed of the air is estimated from the path of the center of the thermal. The tracks of the storks were not modified, they show the original GPS locations, and the viewpoint of the visualisation is moving with the center of mass of the flock. The video plays 10x the normal speed. Note the dynamics of the synchronised subgroups.