Christopher Intaliata: this is Scientific american60 seconds of science. This is Christopher Intagliata.
Songbirds can migrate thousands of miles around the world. They have many tools to find their way.
Henryk Mulrison: They can use stars, they can use the sun, they can use scents, they can use landmarks. They can use more or less anything that helps them.
Henryk Mulison He is a biologist at the University of Oldenburg in Germany. Together with an international team of scientists, he studied another sense that birds can use to help them-the earth’s magnetic field.
Peter Hall Is a physical chemist from the team at Oxford University in the UK
Hall: We know that magnetic sensors are in the eyes of birds and in their retinas. The most likely molecule is the protein cryptochrome.
Ingria Tower: But what they don’t know is: How does this light-sensitive protein, cryptochrome, actually help birds perceive magnetic fields? To find out, they started making some from the genome of the European robin (a migratory species).
Mulison: Basically, we obtained the genetic code from songbirds migrating at night-put it in a bacterial cell culture and asked the culture to make this protein. Then we sent this protein to Oxford.
Ingria Tower: Hall’s colleagues in Oxford then irradiated the protein samples with blue light-turning them into magnetically sensitive molecules. When they did this, they exposed the protein to a magnetic field, which caused two competing chemical reactions to occur.
Hall: We have been able to prove that these chemical reactions are affected by very weak magnetic fields.
Ingria Tower: In fact, the strength of the magnetic field affects how many proteins fall along one of these chemical reaction pathways and the other.
What will happen next from the bird’s eye view is not entirely clear. But they believe that one of the magnetosensitive reactions will produce a protein with a different shape-which may cause it to interact differently with other proteins in avian cells. In turn, this may trigger a series of information transfers, which will enable birds to “perceive” the magnetic field.
Mulison: We also have some indications that cryptochromes from migratory birds may be more sensitive to magnetic fields than chicken cryptochromes. For example, it does not migrate…
Ingria Tower: This is another evidence that the cryptochrome protein may support the magnetism of the robin.Research results are published in journals nature. [Jingjing Xu et al., Magnetic sensitivity of cryptochrome 4 from a migratory songbird]
This experiment only tested proteins outside the eyes of birds. Scientists hope that one day they will be able to measure this effect in animals-to obtain a true bird’s-eye view.
[The above text is a transcript of this podcast.]