Birds can "see" magnetic fields, study reports

Researchers believe they have finally figured out how birds easily navigate around the world.

Joseph Scalise | Oct 29, 2019

Two newly published papers show that birds likely use a special protein in their eyes to navigate around the world.

While birds have been the subject of study for centuries, researchers have never fully understood how they travel around the world with such ease. To shed light on that mystery, scientists at Lund University and the Carl von Ossietzky University Oldenburg found evidence that the protein known as Cry4 might be responsible for avian navigation.

Cry4 is from a protein class known as cryptochromes. Such molecules are sensitive to blue light.and help regulate circadian rhythms. Now, researchers have cause to believe they help birds detect magnetic fields as well.

Past research shows that the cryptochromes in birds' eyes allows the animals to orient themselves through a process known as magnetoreception. Scientists also know that birds can only sense magnetic fields if certain wavelengths are available.

To follow up on such research, the teams behind the two new studies looked at both zebra finches and Europeans robins. They looked at the birds by analyzing gene expression of the cryptochromes, Cry1, Cry2, and Cry4.

That showed, while Cry1 and Cry2 fluctuated each day, Cry4 -- which expressed at constant levels -- was the most likely candidate for magnetoreception. That held true for both zebra finches and robins.

"We also found that Cry1a, Cry1b, and Cry2 mRNA display robust circadian oscillation patterns, whereas Cry4 shows only a weak circadian oscillation," the researchers wrote in their study, according to Science Alert.

In addition, the teams also discovered that Cry4 sits in a region of the retina that receives a lot of light. That further adds credence to the idea that it is used for magnetoreception. In addition, European robins have increased their Cry4 expression over time.

While both teams believe more research is needed before anyone can definitively say that Cry4 is responsible for magnetoreception, the evidence laid out in the two studies is quite strong. The next step is to analyze birds with non-functioning Cry4 and see how they perceive magnetic fields. Only then will teams be able to tell just how important the protein is.

The two studies are published in the Journal of the Royal Society Interface, and Current Biology.