Bird navigation is one of the wonders of nature. Consider these feats: arctic terns can fly more than 80,000 km or about 50,000 miles per year, migrating from their breeding grounds in the Arctic all the way to the Antarctic, where they spend the northern winters. The blackpoll warbler, which weighs a mere 12 grams, completes a nonstop flight over the Atlantic Ocean from new England to the Caribbean, where it spends the winter. And some pigeons reliably find their way home after flights of hundreds of kilometers.

How do birds do it? Most likely through a variety of ways, including using visual and olfactory cues. But this can’t be the whole story because some birds can navigate successfully at night and in cloudy conditions. Recent research has shown that the amazing navigation skills of birds also have a lot to do with their sense of the earth’s magnetic field. Interestingly, this research also suggests that quantum effects are at play.

A team of researchers from the Universities of Oxford in the UK and Oldenburg in Germany have accumulated evidence that the magnetic sense in night birds derives from a specific light-sensitive protein in the eye. That protein, called cryptochrome 4, is believed to play a key role in birds’ magnetic sense.

The research group in Oldenburg managed to extract the genetic code for cryptochrome 4 in night-migratory European robins and then produced them in large quantities in the laboratory. The Oxford team then applied a wide range of magnetic resonance tests to study this protein using state-of-the-art equipment. The team also shed light on the mechanism by which the robins’ magnetic sensitivity arises based on electron transfer reactions triggered by the absorption of blue light. Since electrons are quantum mechanical entities, the team performed quantum mechanical calculations which showed that a handful of amino acids that form the cryptochrome 4 protein chain – known as tryptophans – are essential for the magnetic properties of the molecule. In particular, their calculations imply that electrons that hop from one tryptophan to the next become magnetically sensitive, suggesting that the eyes of migratory birds are like tiny compasses that help steer the birds over vast distances. These results, though preliminary, suggest that birds might be able to see the earth’s magnetic field imprinted on its field of vision.

Further Study:

The full paper mentioned on this post is titled, “Magnetic sensitivity of cryptochrome 4 from a migratory songbird”, Nature, 2021. Downloadable from www.nature.com/articles/s41586-021-03618-9.