Study: Pigeons can sense the Earth's magnetic field; ability might allow them to return home

November 25, 2004

CHAPEL HILL - Homing pigeons have intrigued humans for many centuries through their seemingly uncanny ability to find their way home from thousands of miles away. But how they do that has remained a mystery.

Now, through a series of careful behavioral experiments in the laboratory, scientists say they have shown unequivocally for the first time that pigeons have a magnetic sense that goes beyond just a simple magnetic compass. The findings boost the possibility that pigeons -- and maybe other birds as well -- use the Earth's magnetic field to navigate just as sea turtles do.

"Because of their amazing homing ability, pigeons have been used to transport messages since early Egyptian times, and pigeon racing is a popular sport all over the world," said Dr. Cordula V. Mora, a biology fellow in the University of North Carolina at Chapel Hill's College of Arts and Sciences. "In fact, pigeons are often called the poor man's race horse.

"The two main theories are that pigeons smell their way home

or that they have a magnetic map," Mora said. "Our work strongly supports the latter theory, which still remains to be proven in the field."

A report on the studies, which Mora did as part of her doctoral work in New Zealand, appears in the Nov. 25 issue of the journal Nature. Her co-authors are Drs. Michael Walker, Michael Davison and Martin Wild, all professors at the University of Auckland.

"This is a fascinating study in which Cordula managed to train homing pigeons to respond to magnetic fields," said Dr. Kenneth J. Lohmann, Hoggard Distinguished professor of biology at UNC. "It is important news in biology because more than a dozen attempts by others to do this over the years have all failed. Cordula is the first to find a way to make it work."

In the experiments, if the pigeons chose correctly between two platforms located in a tunnel-like chamber, they were rewarded with food, Mora said. Under normal conditions, they would climb onto either of the two platforms randomly in their search for something to eat. But when a magnetic field was present -- induced by coils above and below their chamber -- the birds could be conditioned to climb the correct platform up to 75 percent of the time, which is significantly more often than they would by chance alone.

Once the pigeons were trained to respond to magnetic field stimuli, Mora learned more about the animals' magnetic sense, such as where their likely magnetic receptors are located, Lohmann said.

One set of experiments showed that a small but strong magnet attached to the top of the pigeons' beaks prevented them from going to the correct platform more than half the time. A small, non-magnetic brass weight similarly attached had no such effect, Mora said. Other experiments showed that both local anesthesia in the upper beak area and severing the ophthalmic branch of the trigeminal nerve impaired the birds' ability to detect magnetic fields, while cutting the olfactory nerve, which transfers information about smells, did not.

"Because the magnetic discrimination behavior that the pigeons learned to perform in the laboratory is impaired by various treatments, we can now say that the pigeon's magnetic sense is located in the nasal region and is most likely magnetite-based," Mora said.

Magnetite crystals consist of iron and have magnetic properties. They also have been found in the noses of rainbow trout and have been linked to those fishes' ability to sense magnetic fields, she said.

"For about 30 years, researchers supporting the olfactory hypothesis of pigeon homing have argued that pigeons smell their way home because procedures that impair the sense of smell in the field, like cutting nerves in the nose, disrupt the birds' homing ability," Mora said.

But because those procedures were performed in the nasal region without making sure that the magnetic sense was not simultaneously impaired, the results now have to be regarded with great caution, she said. That is because the disorientated homing behavior could have been a result of disrupting either the olfactory sense or the magnetic sense, or both.

"New experiments need be done in which the sense of smell is impaired without damaging the magnetic sensory system," the scientist said.

At UNC, working with Lohmann, one of the world's top experts on sea turtle navigation, Mora has begun adapting the same procedures to use with the reptiles.

"She has already trained four turtles to press little paddles to get food when a certain kind of magnetic field is present in a tank," Lohmann said. "The experiments are progressing well, and the turtles are learning rapidly. I keep telling Cordula that turtles are smarter than pigeons, but she is not yet convinced."
-end-


University of North Carolina at Chapel Hill

Related Magnetic Field Articles from Brightsurf:

Investigating optical activity under an external magnetic field
A new study published in EPJ B by Chengping Yin, Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, South China, aims to derive an analytical model of optical activity in black phosphorous under an external magnetic field.

Magnetic field and hydrogels could be used to grow new cartilage
Instead of using synthetic materials, Penn Medicine study shows magnets could be used to arrange cells to grow new tissues

Magnetic field with the edge!
This study overturns a dominant six-decade old notion that the giant magnetic field in a high intensity laser produced plasma evolves from the nanometre scale.

Global magnetic field of the solar corona measured for the first time
An international team led by Professor Tian Hui from Peking University has recently measured the global magnetic field of the solar corona for the first time.

Magnetic field of a spiral galaxy
A new image from the VLA dramatically reveals the extended magnetic field of a spiral galaxy seen edge-on from Earth.

How does Earth sustain its magnetic field?
Life as we know it could not exist without Earth's magnetic field and its ability to deflect dangerous ionizing particles.

Scholes finds novel magnetic field effect in diamagnetic molecules
The Princeton University Department of Chemistry publishes research this week proving that an applied magnetic field will interact with the electronic structure of weakly magnetic, or diamagnetic, molecules to induce a magnetic-field effect that, to their knowledge, has never before been documented.

Origins of Earth's magnetic field remain a mystery
The existence of a magnetic field beyond 3.5 billion years ago is still up for debate.

New research provides evidence of strong early magnetic field around Earth
New research from the University of Rochester provides evidence that the magnetic field that first formed around Earth was even stronger than scientists previously believed.

Massive photons in an artificial magnetic field
An international research collaboration from Poland, the UK and Russia has created a two-dimensional system -- a thin optical cavity filled with liquid crystal -- in which they trapped photons.

Read More: Magnetic Field News and Magnetic Field Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.