By directional training, young domestic chickens have been shown to use a magnetic compass; the same method has now been used to analyse the functional characteristics and the physical principles underlying the chicken’s magnetic compass. Tests in magnetic fields with different intensities revealed a functional window around the intensity of the local geomagnetic field, with this window extending further towards lower than towards higher intensities. Testing chickens under monochromatic 465 nm blue and 645 nm red light suggested a wavelength dependency, with orientation possible under blue, but not under red light. Exposing chickens to an oscillating field of 1.566 MHz led to disorientation, identifying an underlying radical pair mechanism. Local anaesthesia of the upper beak, where iron-based structures have been described as potential magnetoreceptors, did not affect the number of correct choices, suggesting that these receptors are not involved in compass orientation. These findings show obvious parallels to the magnetic compass described for European robins, indicating that chicken and small passerines use the same type of magnetic compass mechanism. This suggests that the avian magnetic compass evolved in the common ancestor of all present-day birds to facilitate orientation within the home range.