If cryptochromes or other chemicals in a bird’s eye behave as the new molecule does, they could provide the foundation of a bird’s magnetic sense. Their shape would probably vary slightly, depending on how much time electrons spent at the far end, or those lingering electrons might affect the shape of another, nearby molecule in the eye. And shape determines biological function.

So depending on how far north or south a bird is from the equator, these molecules could be expected to send different signals to its brain, telling the flier whether it is veering east or west and pinpointing its latitude.

No one knows how a bird would perceive this input. “It could be a bright or dark spot that would move around” in the bird’s field of vision, Hore said. Others doubt that birds have, or need, anything more than their magnetite mouths. Joe Kirschvink, an expert in magnetoreception at the California Institute of Technology, noted among other things that Hore’s experiment worked only at very cold temperatures—”a major stumbling block to the suggestion that optical effects in any organism can be used as the basis of a physiological compass,” he said.
-Rick Weiss (The Washington Post)