Figure 1

Orientation of European robins under 424 nm Blue, 502 nm Turquoise and 565 nm Green light of different quantal flux (given on the left side in quanta s^-1m^-2). The triangles at the periphery of the circles mark the mean headings of individual birds, with solid symbols indicating unimodal means and open symbols indicating the preferred end of mean axes (see text). The arrows and double arrows represent the grand mean vectors and grand mean axes, respectively, with the two inner circles marking the 5% (dotted) and 1% significance border of the Rayleigh test [47].