Figure 1.

Circular distribution of second-order mean vanishing bearings of experienced (Frankfurt I, Frankfurt II, Tübingen) and inexperienced (Würzburg) homing pigeons relative to (a) the HD (ΔH) and (b) the direction of the steepest magnetic intensity slope at the point of vanishing (ΔM). Vanishing data were derived from four previously published figures for three lofts in Germany. (i) 49 release sites, Frankfurt loft I (fig. 1 in Grüter et al. 1982). (ii) 45 release sites, Frankfurt loft II (fig. 8 in Wiltschko 1992). (iii) 29 release sites, Tübingen loft (fig. 1 in Ganzhorn & Schmidt-Koenig 1988). (iv) 35 release sites, Würzburg loft (fig. 3.4 in Wallraff 2005). The direction of (a) home and (b) the steepest magnetic intensity slope is indicated by a dashed line. The overall mean vanishing vector for each dataset is indicated by a black arrow. Each distribution was tested for non-randomness with the Rayleigh test.