The present paper discusses a mechanism of avian magnetoreception, which is based on the interaction of magnetiteand maghemite micro particles, recently found in subcellular compartments within the sensory dendrites of the upper beak of several bird species. The analysis of forces acting between the iron particles shows that the orientation of the external geomagnetic field can significantly change the probability of the mechanosensitive ion channels opening and closing inducing a primary receptor potential via strain-sensitive membrane channels leading to a certain bird orientation effect. The performed theoretical analysis shows that the suggested magnetoreceptor system might be a sensitive biological magnetometer involved in avian magnetoreception process.