Recently, a dispute on the presence or absence of asymmetry of the avian magnetic compass was discussed in Nature (Nature, 2011, 471: E12-13). A new study from biologists in Frankfurt and biopsychologists in Bochum could clarify some of the contradictions. They now revealed that the lateralized magnetic compass of the migratory European robin is not asymmetrically organized from the ontogenetic beginning, but develops as the birds grow older. During first migration in autumn, juvenile robins can orient by their magnetic compass with both eyes. In the following spring, however, the magnetic compass is already lateralized towards the right eye/left hemisphere, but this lateralization is still flexible: it could be removed by covering the right eye for 6 h. During the following autumn migration, the lateralization becomes more strongly fixed, with a 6 h occlusion of the right eye no longer having an effect. This change from a bilateral to a lateralized magnetic compass appears to be a maturation process, the first such case known so far in birds. Because both eyes mediate identical information about the geomagnetic field, brain asymmetry for the magnetic compass could increase efficiency by setting the other hemisphere free for other processes.

Gehring, D., Wiltschko, W., Güntürkün, O., Denzau, S., Wiltschko, R. (2012). Development of lateralization of the magnetic compass in a migratory bird. Proc. R. Soc. B, 279, 4230-4235.