Birds may 'see' Earth's magnetism

Jonathan Wood

Research published in PNAS this week reveals more about how a chemical compass could enable migrating birds to find their way.

‘Evidence is steadily accumulating to back up the idea that chemical reactions in the eyes of birds could help them navigate using the Earth’s magnetic field,’ says Peter Hore of Oxford's Department of Chemistry, co-author of the paper.

‘We have shown that a magnetic field has a small effect on the photochemistry of a protein called photolyase.'

Photolyase is closely related in terms of structure and properties to another protein found in birds’ eyes called cryptochrome which is thought to be at the heart of the compass sensor.

The results suggest that birds may ‘see’ the Earth’s magnetic field lines through variations in chemical reactions going on in their eyes. Such a compass could help them navigate during migrations.

Although the researchers used a magnetic field around 200 times bigger than that of the Earth, it is the first time a biological system closely related to that found in birds has been shown to be sensitive to a magnetic field.

The work is a collaboration between researchers at Oxford University, led by Dr Christiane Timmel and Professor Hore, and scientists at the Universities of Freiburg, Berlin and Munich.

The researchers previously reported that an artificial chemical system could detect weak magnetic fields and respond to their directions as a proof-of-principle of a chemical compass.

Peter told us: ‘It’s early days, but I feel that, if we get the conditions right in the lab, we will be able to see a larger effect and at weaker magnetic fields. That could mimic what happens in a migrating bird’s eye.’