Currently, theoretical, behavioral and physiological evidences support two magnetic sensing hypotheses: a magnetite -
mediated magnetic sense [4]--[6] and / or a vision - mediated magnetic compass [7].
The magnetite - mediated mechanism seems to act as part of a magnetic map - or signpost sense, which could provide the animal with information about its geographic position, whereas the vision -
mediated magnetic sense seems to be a pure compass sense that is based on radical - pair processes in the birds» eye (s)[for reviews], [see e.g. 8, 9].