While birds may appear to flutter about in the world, magically finding their way to food and other members of the flock, the reality is, many species migrate to the same destination, time and again. Over the years, researchers have established that the animals use Earth’s magnetic fields as guides. However, how they sense these fields has been a mystery.
One theory suggested specific molecules in the birds’ eyes were receptive to magnetism, while another claimed it was the iron-rich cells on their beaks that helped with the complex navigation task. Now, two studies – one focused on zebra finches and the other on European robins — assert that the animal’s “sixth sense” for magnetic fields may indeed be due to a special light-sensitive protein called Cry4 found in their eyes.