Avian magnetic compass: Its functional properties and physical basis

摘要

The avian magnetic compass was analyzed in bird species of three different orders - Passeriforms, Columbiforms andGalliforms - and in three different behavioral contexts, namely migratory orientation, homing and directional conditioning. Therespective findings indicate similar functional properties: it is an inclination compass that works only within a functional windowaround the ambient magnetic field intensity; it tends to be lateralized in favor of the right eye, and it is wavelength-dependent,requiring light from the short-wavelength range of the spectrum. The underlying physical mechanisms have been identified asradical pair processes, spin-chemical reactions in specialized photopigments. The iron-based receptors in the upper beak do notseem to be involved. The existence of the same type of magnetic compass in only very distantly related bird species suggests thatit may have been present already in the common ancestors of all modern birds, where it evolved as an all-purpose compassmechanism for orientation within the home range [Current Zoology 56 (3): 265-276, 2010].