SUBTLE SIGNAL. “The problem for a bird wanting to use a magnetic map is that the average change in magnetic field intensity is only c. 3 nT/km on the North-South axis: The geomagnetic field changes c. 30,000 nT from one of the magnetic poles to the magnetic equator, which are c. 10,000km apart. Likewise, magnetic inclination changes only c. 0.009°/km along the North-South axis (a 90° change over 10,000km).”
https://lnkd.in/eUbuD-a