Quantum effects in biology: Bird navigation

Birds possess a physiological magnetic compass, enabling them to make correct directional choices during their migratory flights. The biophysical basis of this compass remains unknown. One of the two major hypotheses postulates that birds use a light-induced radical pair reaction involving coherent spin evolution of two electrons as the foundation of their magnetic compass sensor. This hypothesis has received significant attention during the past decade. Here, we review the growing body of chemical, biophysical, behavioral, and neurobiological evidence suggesting that this quantum-based mechanism may indeed form the basis of the avian magnetic compass.