Setup of the experimental arena.

<div><p>Shown are the positions of the perches in relation to the scale of the tunnel (not shown in full length) for Experiment 1 (A), Experiments 2, 3 and 5 (B), and Experiment 4 (C). </p> <p>The starting positions of the bird, (or birds), and the position of the camera are indicated by the respective symbols. In (B) the 12 subdivisions of the long perch are shown as alternately black and white only for a clearer visualization of their geometry. </p>