Figure 3.

Forward flight velocity declined for visual stimuli that disrupted pattern velocity cues. (a) The forward velocity effects, after accounting for position in the tunnel and individual bird trajectory identities, are shown for all 23 treatments. Control treatments with static stimuli are shown with full opacity, and motion treatments are shown with lower opacity. Treatments with either stimulus motion or static horizontal gratings (i.e. that convey no forward pattern velocity) on the side walls resulted in reduced forward velocity. Circles indicate means and lines indicate 95% confidence intervals. (b) This result led us to analyse the velocity data from a previous study with a narrower chamber, which used asymmetrical side-wall patterns to test for stimulus effects on centring [11]. The narrower chamber led to slower velocities overall, but this analysis also supports the observation that reliable pattern velocity cues, specifically a static vertical grating on at least one side wall, generally led to faster forward velocity.