European Robin May Use Earth’s Magnetic Field to Aid Migration

reaction of protein in robin's eye gives evidence of internal magnetic compass

By Jonny Lupsha, Wondrium Staff Writer

A protein in the eyes of a European robin may sense Earth’s magnetic field. Scientists proved that the protein responded differently to the same light under varying magnetic conditions. Birds use many tools to navigate during migration.

Flock of birds migrating
Migratory birds use the Sun, the constellations, and magnetic field signals as guides to know their location as they travel. Photo By pinthong nakon / Shutterstock

The European robin is a small, migrating songbird that crosses the European continent for the winter. Recently, scientists observed a unique response to light in one of the proteins that the robin has in its eyes. Testing their hypothesis both inside and outside of a weak magnetic field, they observed how the bird’s eyes changed when exposed to continuous light and flashes of light.

The quantum entanglement of two electrons in the protein indicate an innate response to Earth’s magnetic field. Before his unfortunate passing, Dr. Bruce E. Fleury, who was a Professor in the Practice in the Department of Ecology and Evolutionary Biology at Tulane University, explained in his video series The Scientific Wonder of Birds some of the tools migratory birds use.

The Secret Lives of Birds

Birds’ homing senses are incredible feats of nature. Homing pigeons, for example, made up the world’s first airmail service, which connected Great Barrier Island to New Zealand. They also served a role during the Normandy Invasion, carrying messages from resistance fighters in occupied territory.

“A Manx shearwater, carried from Wales to Boston, was found back in its nest 12.5 days later,” Dr. Fleury said. “A Laysan albatross displaced by 6,650 kilometers—that’s over 4,000 miles—took 32 days to find its way back to its nest. Tim and Janet Williams calculated that the equivalent physical demand for a human being would be running a 4-minute mile for 80 hours straight.”

Many birds rely on visual landmarks for their migration. Dr. Fleury said they are often following rivers and shorelines, flying along mountain ranges and funneling through mountain passes. Despite the common insult of someone being “bird-brained,” birds can use several clues to orient themselves.

The relative position of sunlight offers a navigational tool for migratory birds as well, though they must learn to compensate for the changing position of the Sun. Buntings can even navigate by the positions of constellations in the sky, like sailors.

Use of the Magnetic Field

The observation of the European robin’s eye reacting to light in or out of a magnetic field is a distinct find, but it isn’t the first-ever indication of birds using Earth’s magnetic field to navigate.

“William Keeton, in the early 1970s, used tiny bar magnets to show that homing pigeons could orient by magnetic field,” Dr. Fleury said. “He attached bar magnets to the necks of an experimental group, and non-magnetic brass bars to the necks of a control group.

“On sunny days, the magnets had no effect, but on overcast days, when the birds switched to magnetic orientation, only the non-magnetized group could find their way home.”

In another experiment, two scientists designed small electromagnetic caps for homing pigeons. According to Dr. Fleury, the caps could generate a magnetic field directly through the pigeon’s head. On overcast days, pigeons would fly in the opposite direction when the scientists flipped the polarity in the caps.

The homing pigeons needed to be exposed to an hour of sunlight per day in order to snap out of the confusing magnetic field signals.

“Their magnetic compass doesn’t come with clearly labeled north or south; it also needs to be calibrated, probably by comparing it with their solar compass,” Dr. Fleury said. “Once the solar and magnetic compasses are synched together, they can switch between the two as needed. Pigeons raised in the absence of sunlight miss the chance to calibrate their magnetic compass, and never learn to navigate on overcast days.”

Edited by Angela Shoemaker, Wondrium Daily