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Fig. 2. Typical flight path. (A–H) The head turn movement during a flight is
shown in an example with the stimulus sequence LS 3-2, with a 700 ms stimulus
delay. (I) The same flight as in A–H shown from above. The individual
images of the flight path recorded by camera C1
(Fig. 1, 25 Hz sampling rate)
are overlaid. (J) As in I, images of a flight sequence are overlaid. The
initial stimulus was emitted by LS 3, the in-flight stimulus by LS 1 with a
900 ms delay. The reflections of the head tracker are visible as a white,
dotted line. The body and wings appear as low-contrast shades (small arrows).
The positions of the speakers LS 1 to LS 4 are marked with circles. The
turning angle, 
, in degrees was calculated by extending the lines
formed by the head tracker reflections before and after the correction turn,
which appears as a sharp discontinuity in the trace of tracker reflections
(white arrow). Although the trajectory could be curved, only the first
prominent discontinuity corresponded to the saccadic head turn visible in the
frontal view (C1) and was used for determination of the turning angle. The
remaining (or error) angle β to the target is given as the angular
difference between the actual flight trajectory and the extended line to the
center of the target speaker. Note that the room is not lit, but the images
were recorded with infrared cameras.
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