You don't need any magnetic field to distinguish the north-south direction. It is simply the direction shadows are cast when the sun is at its brightest. Conseq

You don't need any magnetic field to distinguish the north-south direction. It is simply the direction shadows are cast when the sun is at its brightest. Consequently, plants will have adjusted to it, providing many (subconscious) clues. The sun makes things strongly non-isotropic, and these clues are everywhere; in the light, in the plants, in the wind, in sound, in urban planning, etc. I expect most of the anecdotal 'evidence' to be explained by this. What would compel me is if randomly changing the magnetic field correlates with the observations, which is what this study seems to have done.