How Birds Harness the Earth’s Magnetic Field for Nighttime Navigation

The Earth’s magnetic field is not only a barrier against the Sun’s cosmic radiation, it also serves as a navigation system for certain animals, such as salmon, sea turtles, and migratory birds. But the question remains, how do they perceive and use this invisible force?

Researchers at the Advanced Facility for Avian Research (AFAR) at Western University have been probing this intriguing question. AFAR, home to the world’s premier hypobaric climatic wind tunnel for bird flight studies, has been focusing on a region in the avian brain known as “cluster N”. This particular region is what migratory birds use to sense the Earth’s magnetic field.

The interesting part is the selective activation of this region. Birds have the ability to engage or disengage their geomagnetic sense based on their needs, akin to how humans selectively attend to stimuli like music.

Under the leadership of psychology PhD candidate Madeleine Brodbeck and AFAR co-director Scott MacDougall-Shackleton, the team scrutinized the behavior of white-throated sparrows. They discovered that these birds activate the cluster N region during nighttime migration, but it goes dormant during rest periods at stopover sites.

“This is the first demonstration of this brain region functioning in a North American bird species, as all prior research in this area was completed in Europe,” the team reported.

“This brain region is super important for activating the geomagnetic compass, especially for songbirds when they migrate at night,” Brodbeck elaborated. “Almost all previous work on this specific brain function was done at one lab in Europe, so it was great to replicate it in a North American bird like the white-throated sparrow.”

The Earth’s magnetic field, first investigated by the German mathematician Carl Friedrich Gauss in the 1830s, continues to captivate physicists, aerospace engineers, and even literature figures like Frank Herbert and Stephen King. Brodbeck shares this fascination.

“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,” Brodbeck said. “For birds, using Earth’s magnetic field to know if they’re going towards a pole or towards the equator is obviously really helpful for orientation and migration. It’s incredible that they can activate their brain in this way, and we can’t.”

Understanding the mechanisms animals use to navigate is a critical area of research, emphasized MacDougall-Shackleton, a psychology professor and cognitive neuroscientist.

“If we want to understand bird migration or how other animals move from one place to another, we need to know how they do it. And more importantly, we need to know what we’re doing, as humans, that might influence them,” MacDougall-Shackleton pointed out.

Their findings were published in the European Journal of Neuroscience.

However, birds’ navigation isn’t solely dependent on the Earth’s magnetic field. MacDougall-Shackleton noted, “Birds don’t just use their magnetic compass. We know they pay attention to the Sun and the stars as cues too. And we also know that things like lights at night, or windows in buildings, and all these things that we put in the world disrupt their migrations. 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.”

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