A study of garden warblers in Europe suggests that migrating birds can see the Earth's magnetic field.
Now work by Dominik Heyers and colleagues at the University of Oldenburg in Germany has started to unravel the mechanism at a neuroanatomical level -- and it shows the eye is key.The published paper is available at PLoS ONE.
Magnetic sensing molecules in the eye, known as cryptochromes, appear to stimulate photoreceptors depending on the orientation of the magnetic field.
This strongly suggests migratory birds perceive the magnetic field as a visual pattern, the researchers said.
"It's a pity we cannot ask them, but what we imagine is that it is like a shadow or a light spot on the normal vision of the bird," Heyers said in a telephone interview.