TY - JOUR

T1 - A refined magnetic pulse treatment method for magnetic navigation experiments with adequate sham control: a case study on free-flying songbirds

AU - Karwinkel, Thiemo

AU - Winklhofer, Michael

AU - Allenstein, Dario

AU - Burst, Vera

AU - Christoph, Paula

AU - Holland, Richard

AU - Huppop, Ommo

AU - Steen, Jan

AU - Bairlein, Franz

AU - Schamaljohann, Heiko

PY - 2024/5/15

Y1 - 2024/5/15

N2 - Migratory songbirds may navigate by extracting positional information fromthe geomagnetic field, potentially with a magnetic-particle-based receptor.Previous studies assessed this hypothesis experimentally by exposing birdsto a strong but brief magnetic pulse aimed at remagnetizing the particlesand evoking an altered behaviour. Critically, such studies were not ideallydesigned because they lacked an adequate sham treatment controlling forthe induced electric field that is fundamentally associated with a magneticpulse. Consequently, we designed a sham-controlled magnetic-pulse experiment, with sham and treatment pulse producing a similar induced electricfield, while limiting the sham magnetic field to a value that is deemed insufficientto remagnetize particles. We tested this novel approach by pulsing morethan 250 wild, migrating European robins (Erithacus rubecula) during twoautumn seasons. After pulsing them, five traits of free-flight migratory behaviourwere observed, but no effect of the pulse could be found. Notably, one ofthe traits, the migratory motivation of adults, was significantly affected in onlyone of the two study years. Considering the problem of reproducingexperiments with wild animals, we recommend amulti-year approach encompassing large sample size, blinded design and built-in sham control to obtain future insights into the role of magnetic-particle-based magnetoreception in bird navigation.

AB - Migratory songbirds may navigate by extracting positional information fromthe geomagnetic field, potentially with a magnetic-particle-based receptor.Previous studies assessed this hypothesis experimentally by exposing birdsto a strong but brief magnetic pulse aimed at remagnetizing the particlesand evoking an altered behaviour. Critically, such studies were not ideallydesigned because they lacked an adequate sham treatment controlling forthe induced electric field that is fundamentally associated with a magneticpulse. Consequently, we designed a sham-controlled magnetic-pulse experiment, with sham and treatment pulse producing a similar induced electricfield, while limiting the sham magnetic field to a value that is deemed insufficientto remagnetize particles. We tested this novel approach by pulsing morethan 250 wild, migrating European robins (Erithacus rubecula) during twoautumn seasons. After pulsing them, five traits of free-flight migratory behaviourwere observed, but no effect of the pulse could be found. Notably, one ofthe traits, the migratory motivation of adults, was significantly affected in onlyone of the two study years. Considering the problem of reproducingexperiments with wild animals, we recommend amulti-year approach encompassing large sample size, blinded design and built-in sham control to obtain future insights into the role of magnetic-particle-based magnetoreception in bird navigation.

U2 - 10.1098/rsif.2023.0745

DO - 10.1098/rsif.2023.0745

M3 - Article

VL - 21

JO - Journal of the Royal Society: Interface

JF - Journal of the Royal Society: Interface

SN - 1742-5662

IS - 214

ER -