The European robin and other birds know where to migrate by sensing the direction of the Earth’s magnetic field. Researchers have recently attributed this ability to a chemical reaction that takes place within the eye and whose success depends on the field direction. However, University of Oxford researchers report October 3 in Biophysical Journal that the current form of this “radical-pair mechanism” is not sensitive enough to explain the disruption of the avian magnetic compass by certain radiofrequency magnetic fields, raising new questions about this popular example of quantum biology.