The mean orientation recorded under overcast skies in the local geomagnetic field was for all three species directed south to southeast (Fig. 1B, Fig. 2B, Fig. 3B; Table 2).
Each group is described by its centroid and mean orientation.
Geological units with low mechanical strength promote the occurrence of breakouts and can rotate the stress field as much as 90° from the mean orientation, which is indicated by high breakout-densities in clay-rich intervals and a deviation of their mean orientation.
According to Table 2, the mean orientation under simulated overcast skies and in the local geomagnetic field was directed south for the dunnock (α = 182°, Fig. 1D) and the European robin (α = 175°, Fig. 2D), and south south-east for the sedge warblers (α = 156°, Fig. 3D).
We found significant mean orientation (α = 267°, r = 0.43, p<0.001) under clear skies in a vertical magnetic field after cue-conflict exposure for the European robin (Fig. 2C; Table 2), with a higher scatter compared to the control tests.
Mean orientation of the lines is N37.5°W.
The distribution is arranged to set the mean orientation = 90°, corresponding to the mean orientation of the lineation.
The mean orientation of each bird was recorded under the following experimental conditions: (1) natural clear skies (cloud cover 0 1/8) in the local geomagnetic field, and (2) simulated overcast skies under diffusing Plexiglas in the local geomagnetic field.
We found that the mean orientation of data from all our experimental birds which prior to the cue-conflict experiment experienced a +90° shift of the horizontal component of the magnetic field, were not significantly different from random (α = 75°, r = 0.21, N = 27, p>0.05).
"Sadeh" means field: as in field of study, of action.
