Short-term antibiotics, induced magnetic field, and magnetic sensitivity in a migratory songbird

The use of magnetoreception is widespread in the animal kingdom. Although much effort has been invested in unraveling the receptor and the mechanism behind this ability, the results remain inconclusive. The recently proposed symbiotic magnetic sensing hypothesis suggests that magnetotactic bacteria symbiotically act as magnetic sensors for the host. In this study, we examined the changes in magnetic orientation of Eurasian reed warblers (Acrocephalus scirpaceus) placed in Emlen funnels under the influence of antibiotics, in response to a manipulated magnetic field. We found that reed warblers of the control group showed no significant magnetic orientation when placed in a manipulated magnetic field. In contrast, reed warblers placed in an unplugged coil showed significant magnetic southwest orientation. Furthermore, reed warblers exposed to short-term antibiotic treatment (12 h) demonstrated significant magnetic orientation (southwest, regardless of season) and significantly lower directional variance. We hypothesize that individuals from the control group identified the electromagnetic noise induced by the artificial magnetic field. Taken together, this unexpected result may demonstrate the sensitivity of passerines to electromagnetic noise and a possible damping effect of antibiotics on this sensitivity. Assuming our interpretations are correct, we consider this result as indirect experimental support for the symbiotic magnetic sensing hypothesis.