A magnetic pulse does not affect homing pigeon navigation: a GPS tracking experiment

Abstract

SUMMARYThe cues by which homing pigeons are able to return to a home loft after displacement to unfamiliar release sites remain debated. A number of experiments in which migratory birds have been treated with a magnetic pulse have produced a disruption in their orientation, which argues that a ferrimagnetic sense is used for navigation in birds. One previous experiment has also indicated an effect of magnetic pulses on homing pigeon navigation, although with inconsistent results. Previous studies have shown that some magnetic-related information is transmitted by the trigeminal nerve to the brain in some bird species, including the homing pigeon. The function of this information is still unclear. It has been suggested that this information is important for navigation. Previous studies with trigeminal nerve lesioned homing pigeons have clearly shown that the lack of trigeminally mediated information, even if magnetic, is not crucial for homing performance. However, this result does not completely exclude the possibility that other ferrimagnetic receptors in the homing pigeon play a role in navigation. Additionally, recent studies on homing pigeons suggested the existence of a ferrimagnetic sense in a novel location presumably located in the inner ear (lagena). In the present study, we tested whether any ferrimagnetic magnetoreceptors, irrespective of their location in the birdʼs head, are involved in pigeonsʼ homing. To do this, we treated homing pigeons with a strong magnetic pulse before release, tracked birds with GPS loggers and analyzed whether this treatment affected homing performance. In the single previous magnetic pulse experiment on homing pigeons, only initial orientation at a release site was considered and the results were inconsistent. We observed no effect of the magnetic pulse at any of the sites used on initial orientation, homing performance, tortuosity or track efficiency, which does not support a role for the ferrimagnetic sense in homing pigeon navigation, at least not in this geographic area, where magnetic field variations are in the region of 200nT intensity and 0.8deg inclination. Supplementary material available online at

Conditioned discrimination of magnetic inclination in a spatial-orientation arena task by homing pigeons (Columba livia)

“…Furthermore, magnetic pulse treatments under sunny conditions shifted the initial orientation direction of homing pigeons, thus providing further indication of the possible existence of a magnetic map (Beason et al, 1997). It should be noted though that such a pulse effect was not replicated in a recent study with GPS-tracked homing pigeons (Holland et al, 2013), which found no evidence of impairment of either initial orientation or navigation performance. Furthermore, there is also considerable evidence, which is not necessarily mutually exclusive to the possibility of the existence of a magnetic map, that homing pigeons use odours in the atmosphere at least at some locations on Earth to determine their position (for reviews, see Papi, 1992;Wallraff, 2004;Wallraff, 2006).…”

True navigation in migrating gulls requires intact olfactory nerves

“…While there has been great effort in attempting to understand the physiological basis of magnetite-based magnetoreception 15 , outside the laboratory a number of experiments, particularly those reporting tracking data, have not provided support for its role in the navigational map 10 14 17 32 33 34 35 36 37 . In contrast, the olfactory sense, long neglected in avian species, is increasingly demonstrated to be important in birds’ biology 38 including navigation.…”

Magnetoreception in birds

“…The response to the pulse was restricted to experienced migrants that navigate towards an already familiar goal, whereas young birds on their first migration that fly innate courses were not affected [92]. This finding and the observation that homing pigeons treated with such a pulse deviated from untreated controls at some (but not all) sites in greater distances from home [93,94] indicate that the pulse affects a receptor that provides birds with a magnetic component of the navigational ‘map’ (see also [95]). Apparently, the pulse changes the course to be pursued, while the magnetic inclination compass remains unaffected [92,96].…”