Birds can switch their perception of Earth’s magnetic field on and off

Researchers at Western’s Advanced Facility for Avian Research (AFAR) have made a remarkable discovery about birds: they can quite literally flick a brain switch to perceive Earth’s magnetic field. 

The study sheds new light on the intriguing manner in which migratory birds navigate, highlighting the importance of a brain region called “Cluster N” for processing geomagnetic information.

For context, it’s vital to recognize that the Earth’s magnetic field extends far into space. This protective layer, caused by the flow of molten iron within our planet’s inner core, serves as our shield against the harmful cosmic radiation the Sun emits. 

Yet, for some members of the animal kingdom, this invisible force is a natural GPS. Salmon, sea turtles, and migratory birds use the magnetic field to navigate across vast distances.

The process of how and why this happens has been somewhat of a mystery. The new study, led by PhD candidate Madeleine Brodbeck and AFAR co-director Scott MacDougall-Shackleton, has begun to unravel this mystery. The research was focused on white-throated sparrows.

What the researchers discovered 

The team found that these birds have the ability to activate Cluster N in their brains at night when they were motivated to migrate. This activation allows the birds to avoid prey and fly during cooler periods. But the birds are also capable of making the region go dormant when they are ready to rest.

Brodbeck explained: “This brain region is super important for activating the geomagnetic compass, especially for songbirds when they migrate at night.” The study represents the first evidence of this brain region functioning in a North American bird species, and it builds upon the previous work that was primarily conducted in Europe.

For decades, Earth’s magnetic field has intrigued not only physicists and aerospace engineers, but also creative minds, inspiring the works of renowned science fiction writers like Frank Herbert and Stephen King. The concept of invisible forces guiding our movements, wholly imperceptible to humans, continues to be a fascination for Brodbeck as well.

“Magnetic fields are really fun to think about because they’re invisible to humans. We can’t see them or sense them, but most animals perceive them in some way,” said Brodbeck.

Significance of the study

To navigate and migrate, birds rely not just on Earth’s magnetic field, but also on visual cues from the sun and the stars. Unfortunately, our increasingly urbanized landscapes, dotted with artificial lights and glass skyscrapers, disrupt their migratory paths.

“This type of basic research informs us and lets us know the full suite of ways that animals perceive the world when they’re migrating and what we as humans need to do to minimize our impact,” said Professor MacDougall-Shackleton. 

He emphasized that understanding the physical mechanisms of animal movement isn’t just academic; it’s fundamentally important in order to comprehend and possibly mitigate the ways human actions influence their journeys.

This groundbreaking study, published in the European Journal of Neuroscience, underlines the need for continued exploration into the complex mechanisms that drive animal behaviors. Furthermore, it also provides a perspective into our responsibility towards co-inhabitants of our planet, as our actions inevitably leave a footprint on their migratory paths.

More about Earth’s magnetic field

Earth’s magnetic field is a powerful, invisible force that extends from the interior of the planet out into space. It originates from the flow of molten iron and nickel in the planet’s outer core, which creates electric currents that, in turn, generate the magnetic field. This is known as the dynamo effect.

The Earth’s magnetic field is important for several reasons.

Protection from Solar Radiation

The magnetic field shields the Earth from harmful solar radiation. Without it, life as we know it would not exist, because the atmosphere would be stripped away by solar winds – streams of charged particles from the Sun.

Aid to Navigation

The Earth’s magnetic field creates the North and South magnetic poles, which are slightly offset from the geographic poles. These magnetic poles are the basis for magnetic navigation, used by both humans and many animals. Animals such as birds, sea turtles, and even some types of bacteria can sense the Earth’s magnetic field and use it to navigate.

Generation of Auroras

The Earth’s magnetic field is also responsible for phenomena like the Aurora Borealis (Northern Lights) and Aurora Australis (Southern Lights). These occur when charged particles from the Sun are trapped in the Earth’s magnetic field and collide with atmospheric atoms and molecules, causing them to emit light.

The Earth’s magnetic field is not static. Over millions of years, it has undergone numerous reversals, where the North and South magnetic poles switch places. The last reversal, known as the Brunhes-Matuyama reversal, occurred approximately 780,000 years ago. 

Scientists are still investigating why these reversals occur, but it is believed that changes in the flow of molten iron and nickel in the Earth’s outer core are responsible.

Despite its importance, many mysteries remain about the Earth’s magnetic field. As studies like the one at Western’s Advanced Facility for Avian Research (AFAR) continue, our understanding of this complex and vital part of our planet will continue to grow.

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