Birds have good vision, but their brains turn out to be even more eagle-eyed. Having previously found that molecules called cryptochromes embedded in birds’ retinas both respond to light and detect magnetic fields, scientists at the University of Oldenburg in Germany recently showed that avian brains incorporate clever mechanisms for processing the geomagnetic information.
By using tracer chemicals in experiments with live garden warblers, the researchers followed a circuit of neurons from the cryptochrome molecules to the “cluster N” area of the brain, which is active during navigation, showing for the first time that cluster N uses information from the retina. Scientists aren’t sure how such compass directions appear in the eyes of migratory birds, but team member Dominik Heyers has a guess. “If a bird looks north or south, it somehow has a light spot or a dark spot there,” he says.
Another navigational tool: birds’ beaks, which contain bits of magnetite, a mineral that may allow them to sense Earth’s magnetic field. Since the field is stronger near the poles, the magnetite gives birds crucial information about their latitude.
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