Fig. 2

Flight height above ground (A–B and E–F) and flight speed (C–D and G–H) for flights during traveling segments for 39 tracked Caspian terns during autumn (A, C, E, G) and spring (B, D, F, H) migration. Flights were defined when birds had an instantaneous speed greater than 10 km/h both at the start and end of 30-min intervals. Panels on the top row of the figure show all recorded flights, with nighttime (blue), daytime (yellow), and dusk or dawn (pink) indicated by colors (A–D). Extreme values of flight heights above the ground that resulted from unreliable GPS reads (> 6,000 m and with unrealistic climb rates or < 0 m agl) were excluded from the graph. The bottom row of the figure shows the smoothed lines of average speed and height above ground (E–H), with lines representing average values and shaded areas the 95% confidence interval. Note that since the graphs of the bottom row represent averages the scales of the y axis between top and bottom panels differ. The proportion of recorded flights was calculated as the number of identified flights compared to total relocations for each hour, and it is included as a green line in panels G and H and referenced by the right axis