Fig. 4. (A) Observed flight paths of the four birds, (B) average overall and vertical flight speeds during the digitized wingbeat and (C) wingbeat frequency versus vertical flight angle. (A) Average paths traveled by the pigeons for each flight angle during one wingbeat, with starting position normalized to the origin. Vertical distances traveled were similar between 30° and 60° flights, and also between –30° and –60° flights. Birds traveled greater horizontal distances for ±30° and 0° flights than for ±60° flights. (B) Overall flight speed (squares) showed an increase from –60° to reach a maximum at –30°. Speed decreased from –30° descent to 60° ascent. The vertical component of flight velocity (triangles) showed the greatest differences between ±30° and 0° flights, and was not significantly different between –30° and –60° descents (P=0.11). (C) Wingbeat frequency (WBF) ranged from 6.1 Hz to 9.6 Hz with greater variability observed among individuals for ascending flight. WBF did not differ significantly across vertical flight angles (P=0.053, F=3.77). In B and C, as well as in subsequent figures, each point is the data for a standard wingbeat, lines connect means of adjacent flight angles, and asterisks indicate significant differences. Data for individual birds are color-coded.