BIRDS that navigate using the Earth’s magnetic field rely more on their eyes than on the magnetic particles in their nostrils, an experiment on robins suggests.

Rival theories of bird navigation have suggested both mechanisms. Now Henrik Mouritsen at the University of Oldenburg, Germany, and his team have show that eyes could be key. In one group of robins, the team removed cluster N, a brain region involved in processing signals from the “pair-forming photopigments” in the eyes thought to relay magnetic compass information. In another group, the team cut the trigeminal nerve, which sends signals to the brain from the magnetic particles in the …