Do Birds See Magnetic Fields?

A curious question which science has never adequately answered is how migratory birds are able to navigate their annual passages. In fact, research in this unlikely area abound and two potential advances in our understanding have recently been published.

One theory, suggested over 40 years ago, that the birds are able to navigate because of molecules which respond to the Earth's magnetic field, though until recently there has been no evidence of such molecules. Research out of the University of Oldenburg in Germany showed that light-sensitive proteins called cryptochromes exist in the retinal neurons of migratory garden warblers. New research indicates that cryptochrome-like molecules are in fact sensitive to magnetic fields, prompting researchers to suggest this as a candidate for the navigation source.

The flaw in these models are that they require the spins of the ions in the retina to align much more quickly than physicists expect to be possible - in other words, the Earth's magnetic field is too weak to have a significant impact that would be noticed by the birds.

However, another new finding, out of the University of Crete, builds on their research that the quantum Zeno effect can be used to enhance a system's sensitivity to magnetic fields. Even a very weak field, in this case, would be able to align the spins of the ions in the bird's retina quickly enough to accomplish the proposed task.

The case is far from conclusive, and the debate rages on ... meanwhile, of course, birds continue to migrate unhindered by humanity's lack of understanding.

Related Articles:

• Nature - Chemical compass model of avian magnetoreception
• Quantitative Biology - Quantum Zeno Effect Underpinning the Radical-Ion-Pair Mechanism of Avian Magnetoreception
• New Scientist - Do birds see with quantum eyes?
• New Scientist - Birds can 'see' the Earth's magnetic field