Bat
Microbats make use of magnetoreception, in that they have a high sensitivity to the Earth's magnetic field, as birds do. Microbats use a polarity-based compass, meaning that they differentiate north from south, unlike birds, which use the strength of the magnetic field to differentiate latitudes, which may be used in long-distance travel. The mechanism is unknown but may involve magnetite particles.
Magnetoreception
For a long time the trigeminal system was the suggested location for a magnetite-based magnetoreceptor in the pigeon. This was based on two findings: First, magnetite-containing cells were reported in specific locations in the upper beak. Subsequent studies, however, revealed that these cells were macrophages, not magnetosensitive neurons. Second, pigeon magnetic field detection is impaired by sectioning the trigeminal nerve and by application of lidocaine, an anesthetic, to the olfactory mucosa. However, lidocaine treatment might lead to unspecific effects and not represent a direct interference with potential magnetoreceptors. Therefore, an involvment of the trigeminal system is still debated. In the search for magnetite receptors a large iron containing organelle (the cuticulosome) in the inner ear of pigeons was discovered. This organelle might represent part of an alternative magnetosensitive system. Taken together the receptor responsible for magnetosensitivity in homing pigeons remains uncertain.