Geomagnetic disturbance associated with increased vagrancy in migratory landbirds

Authors: Benjamin A. Tonelli, Casey Youngflesh, & Morgan W. Tingley

Year: 2023

Publication: Scientific Reports

Publication Link:

Abstract: Rare birds known as “accidentals” or “vagrants” have long captivated birdwatchers and puzzled
biologists, but the drivers of these rare occurrences remain elusive. Errors in orientation or navigation
are considered one potential driver: migratory birds use the Earth’s magnetic field—sensed using
specialized magnetoreceptor structures—to traverse long distances over often unfamiliar terrain.
Disruption to these magnetoreceptors or to the magnetic field itself could potentially cause errors
leading to vagrancy. Using data from 2 million captures of 152 landbird species in North America over
60 years, we demonstrate a strong association between disruption to the Earth’s magnetic field and
avian vagrancy during fall migration. Furthermore, we find that increased solar activity—a disruptor of
the avian magnetoreceptor—generally counteracts this effect, potentially mitigating misorientation
by disabling the ability for birds to use the magnetic field to orient. Our results link a hypothesized
cause of misorientation to the phenomenon of avian vagrancy, further demonstrating the importance
of magnetoreception among the orientation mechanisms of migratory birds. Geomagnetic
disturbance may have important downstream ecological consequences, as vagrants may experience
increased mortality rates or facilitate range expansions of avian populations and the organisms they

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