The takeaway: The magnetic North Pole is moving with increased speed. This will slowly impact bird migrations.
The North Pole sits still, while the magnetic north pole is always on the move–and lately that movement has sped up. That wandering magnetic target matters more than most people realize, and is especially important to birds that rely on Earth’s invisible magnetic lines to chart their epic migrations.
Some birds appear to sense magnetic fields using specialized cells–possibly using magnetite-based mechanisms, providing a sort of internal compass. But as that point drifts faster and further, the maps that birds were used to don’t quite match reality.
In the last few decades, magnetic north’s accelerated march has begun to subtly reshape how some birds navigate from their summer homes to their winter homes–and researchers are watching closely to see how these feathered travelers adapt.
What Is the Magnetic North Pole?
The magnetic north pole is the point on the surface of the Earth where the planet’s magnetic lines point down vertically, toward the molten iron of the Earth’s core. This creates a magnetic field that is not perfectly aligned with the Earth’s axis of rotation.
When you navigate by compass, the needle points toward the magnetic north pole. While the difference is subtle enough that casual use of a compass is not affected, airlines, military, engineers, and navigators need to know the precise location of the magnetic north pole and how it varies from true north. (The angle between them is called “magnetic declination.”)
Because the Earth’s magnetic field is generated by flows of molten iron and nickel–and those flows change over time, the magnetic poles (there’s another one in the south) slowly move. This gradual change is called “polar drift.”
For a long time, polar drift loped along at about 6 miles a year, but beginning in the 1990s, it suddenly sped up to about 30 miles a year. A few centuries ago (and we know this from records kept by early mariners), magnetic north was over Banks Island, Canada, then it moved southeasterly. Roughly a century ago, magnetic north was located just off the north coast of mainland Nunavut, Canada at 70 degrees north, but by 2020, magnetic north had crossed 80 degrees north and is currently not that far from the North Pole. Magnetic north is continuing to drift away from Canada on its way to northern Siberia.
How Birds Use Magnetic North
As the magnetic poles drift, the magnetic field lines that birds use for navigation gradually change. Some studies have shown that sudden changes in magnetic fields confuse young or inexperienced birds, causing them to veer off course during migrations. While some species appear to adjust to shifting poles over time, rapid shifts can temporarily increase the chances of them being thrown off course.
Are Shifting Poles Changing Where Migratory Birds Nest and Mate?
If birds use magnetic north to help guide them on their migratory routes, and magnetic north is shifting, will birds change where they spend their winters and summers? And will this change how they fly between the two? The answer is yes, but barely.
First of all, there is evidence that shifts in magnetic fields can disorient birds mid-flight, but these interruptions are usually temporary. And notably, not all birds rely equally on magnetic navigation–some birds just follow rivers, ridges, and coastlines, for example.
It’s important to keep in mind that the effect of pole drift is real, but gradual and not catastrophic. Birds are adaptable, and even with the increased pace of this change, it’s still relatively slow.
How Birds Choose Nesting and Breeding Grounds
Just like humans choosing a new home, birds use a set of criteria for deciding the location of their summer breeding grounds and winter grounds:
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Habitat availability
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Food supply
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Temperature and climate
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Historical routes and locations
While shifting poles in theory could mean that some birds go off course, keep in mind that these changes are gradual, and over generations, birds can recalibrate their magnetic map, meaning they can usually adjust to slow pole drift.
While it is possible that summer nesting locations could shift slightly if migratory routes are altered, birds will still seek out the same types of habitats. Same thing goes for wintering grounds–the exact location might be different, but the type of location will be the same. This highlights the impact of climate change and habitat loss, which are much stronger influences on wintering and summering locations than magnetic pole drift.
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