How Do Pigeons Find Their Way Home?
Unlocking the secret of how birds navigate.
The pigeon is far more mysterious than meets the eye. Considered a nuisance by many, these birds are the stars of ongoing research into birds' sixth sense: navigation.
From the ancient Romans to the Allied forces in World War II, humans have long used pigeons to carry messages because of their remarkable ability to find their way home. Pigeons and many other migratory birds are thought to use the earth's magnetic fields to stay the course, but scientists aren't sure how our feathered friends detect and process magnetic information. New research is answering some of these questions.
In May scientists reported that brainstem cells associated with the inner ear are activated when a pigeon is exposed to magnetic fields. "The brain cells signal the direction, intensity, and polarity of the earth's magnetic field," says J. David Dickman, a neuroscientist at Baylor College of Medicine in Houston, who lead the research, published in Science. "These signals could be used like a GPS."
Other creatures have internal compasses--trout detect magnetic information through their nose, and migrating loggerhead turtles pick up on both latitude and longitude--but most navigation research has focused on birds.
Until recently, scientists thought that iron-rich neurons in pigeons' beaks transmitted information about magnetic fields to their brains. But another team unexpectedly disproved this theory in April. The researchers discovered that the iron-rich beak cells aren't neurons at all but actually macrophages, or white blood cells that help the bird's immune system. They're loaded with iron because they recycle old red blood cells, says David Keays, lead researcher and a neuroscientist at the Institute of Molecular Pathology in Vienna, Austria. "We found them all over the bird, from the skull to the wings," he says. "They're on patrol for pathogens."
The discovery means that scientists must continue the search for the magnetic field-sensing cells. But they aren't flying blind: Dickman's work hints that those just might be found in the inner ear.