Scott Weidensaul

“It now appears that birds may visualize the earth’s magnetic field through a form of quantum entanglement, which is just as bizarre as it sounds. Quantum mechanics dictates that two particles, created at the same instant, are linked at the most profound level—that they are, in essence, one thing, and remain “entangled” with each other so that regardless of distance, what affects one instantly affects the other. No wonder the technical term in physics for this effect is “spooky action.” Even Einstein was unsettled by the implications. Theoretically, entanglement occurs even across millions of light-years of space, but what happens within the much smaller scale of a bird’s eye may produce that mysterious ability to use the planetary magnetic field. Scientists now believe that wavelengths of blue light strike a migratory bird’s eye, exciting the entangled electrons in a chemical called cryptochrome. The energy from an incoming photon splits an entangled pair of electrons, knocking one into an adjacent cryptochrome molecule—yet the two particles remain entangled. However minute, the distance between them means the electrons react to the planet’s magnetic field in subtly different ways, creating slightly different chemical reactions in the molecules. Microsecond by microsecond, this palette of varying chemical signals, spread across countless entangled pairs of electrons, apparently builds a map in the bird’s eye of the geomagnetic fields through which it is traveling.”
― Scott Weidensaul, A World on the Wing: The Global Odyssey of Migratory Birds