Migratory birds navigate more precisely than any GPS - even after flying several thousand kilometres, they land exactly where they wanted to go. Exactly how this works is not yet fully understood. Researchers led by Oldenburg biologist Henrik Mouritsen have now come a step closer to understanding the phenomenon.
Researchers assume that the birds have several abilities to orientate themselves: They analyse the position of the sun, memorise constellations and perceive the earth's magnetic field. How this works is not yet fully understood. It is highly likely that quantum chemical details in the eye play a decisive role - the so-called "radical-pair mechanism". Until now, however, no one has been able to explain why birds can navigate with such astonishing precision using this mechanism. After many years of collaboration, an international team of researchers from the University of Oxford (UK) and Oldenburg neurobiologist Prof Dr Henrik Mouritsen have developed a promising theory that could now explain this precision. The scientists recently published their findings as the cover story in the renowned journal "Proceedings of the National Academy of Sciences" (PNAS).
The lead author of the specialist article is chemist Prof Dr Peter J. Hore from Oxford. Mouritsen, Director of the Institute of Biology and Environmental Sciences at the University of Oldenburg, acts as co-author. The scientists developed a model of the radical-pair mechanism based on very realistic quantum chemical calculations. In simple terms, the hypothesis is that the magnetic sense of birds is located in special proteins in the retina, the cryptochrome proteins. These are colour-sensitive. When white, blue or turquoise light hits the eye, a chemical reaction occurs: two "radicals" are produced and the bird's magnetic sense is "armed", so to speak. The bird can now read the direction of the magnetic field. If it turns or tilts its head, its perception changes accordingly. Presumably, an image of the earth's magnetic field is superimposed on the optical image that a bird sees.
Using complex computer simulations, the scientists were able to recreate these processes in the eye - with an astonishing result: "The directional accuracy of the radical-pair mechanism may be much better than expected," says Mouritsen. Precision of well under five degrees is even possible. The researchers thus proved that the cryptochrome has the right chemical properties to act as a compass needle for birds. However, this is not yet proof that this theory is correct. According to Mouritsen, further joint experiments are necessary for this. The neurobiologist has high hopes for the radical pair model: "It may one day provide us with a quantum chemical explanation of how birds find their way and why influences such as electrosmog could cause migratory birds' sense of direction to fail."