Packmor, F, Kishkinev, D, Bittermann, F, Kofler, K, Machowetz, C, Zechmeister, T, Zawadzki, L, Guilford, T and Holland, R (2021) A magnet attached to the forehead disrupts magnetic compass orientation in a migratory songbird. The Journal of Experimental Biology. ISSN 0022-0949

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For studies on magnetic compass orientation and navigation performance in small bird species, controlled experiments with orientation cages inside an electromagnetic coil system are the most prominent methodological paradigm. These are, however, not applicable when studying larger bird species and/or orientation behaviour during free flight. For this, researchers have followed a very different approach. By attaching small magnets to birds, they intended to deprive them of access to meaningful magnetic information. Unfortunately, results from studies using this approach appear rather inconsistent. As these are based on experiments with birds under free flight conditions, which usually do not allow exclusion of other potential orientation cues, an assessment of the overall efficacy of this approach is difficult to conduct.
Here, we directly test the efficacy of small magnets for temporarily disrupting magnetic compass orientation in small migratory songbirds using orientation cages under controlled experimental conditions. We found that birds which have access to the Earth’s magnetic field as their sole orientation cue show a general orientation towards their seasonally appropriate migratory direction. When carrying magnets on their forehead under these conditions, the same birds become disoriented. However, under changed conditions that allow birds access to other (i.e. celestial) orientation cues, any disruptive effect of the magnets they carry appears obscured.
Our results provide clear evidence for the efficacy of the magnet approach for temporarily disrupting magnetic compass orientation in birds, but also reveal its limitations for application in experiments under free flight conditions.

Item Type: Article
Additional Information: © 2021. Published by The Company of Biologists Ltd This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed.
Subjects: S Agriculture > S Agriculture (General)
S Agriculture > SF Animal culture
Divisions: Faculty of Natural Sciences > School of Life Sciences
Depositing User: Symplectic
Date Deposited: 29 Oct 2021 11:25
Last Modified: 17 Nov 2021 15:53

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