Birds use ‘magnetic map’ to navigate (even in places they’ve never been)
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Migrating birds are able to correct their navigation using the Earth’s magnetic field – even in places they have never been, new research has shown.
Researchers from Bangor and Keele universities exposed birds to a simulation of Earth’s magnetic field thousands of miles from their normal migration route.
Different parts of the Earth have a distinct "geomagnetic signature" depending on their location.
The birds showed an urge to begin their journey as if they were in the place shown by the magnetic signal, the researchers said.
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The birds oriented themselves to fly in a direction that would lead them "back" to their migratory path from the location suggested by the magnetic signals they were experiencing.
This shows that the Earth's magnetic field is the key factor in guiding reed warblers when they are blown off course.
"The overriding impulse was to respond to the magnetic information they were receiving," said Richard Holland of Bangor University's School of Natural Sciences.
“What our current work shows is that birds are able to sense that they are beyond the bounds of the magnetic fields that are familiar to them from their year-round movements, and are able to extrapolate their position sufficiently from the signals.
“This fascinating ability enables bird to navigate towards their normal migration route."
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This happened despite still being in the same place, and experiencing sensory clues including starlight and sights, smell and sounds.
Florian Packmor of Bangor University said: "We have already shown that the reed warblers use the same magnetic cues experienced within their natural range, but this study shows that they can extrapolate what they understand about how the magnetic field varies in space far beyond any previous experience they have had."
Writing in Current Biology, the team from Bangor and Keele universities describe how reed warblers can navigate from a "magnetic position" beyond what they have experienced in their normal migration route, back towards that correct route.
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Dr Dmitry Kishkinev of Keele University's School of Life Sciences said: "What these birds are achieving is 'true navigation'. In other words, they are able to return to a known goal after displacement to a completely unknown location without relying on familiar surroundings, cues that emanate from the destination, or information collected during the outward journey."
Questions remain about whether the birds have an accurate "map" or are using a "rule of thumb" measurement to judge the general direction of travel needed to get back on course.
The researchers believe the findings could probably also be applied to other migrating songbirds.
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