Say Avians May Be Able To See Magnetic Fields

Are birds able to literally "see" the Earth's magnetic fields? It's a controversial theory in scientific circles... but researchers say it also appears to be a likely one.

The Chicago Tribune reports light-sensitive cells in avian eyes may be able to sense variations between magnetic fields, perceiving those changes as shadows. In conjunction with an internal compass -- which relies on tiny metal filings in the cells of many birds, that "point" in the proper direction -- birds may follow those variations north or south, depending on the season.

"You must put yourself in the brain of the bird," says University of Illinois physicist Klaus Schulten. "We might be surprised, but animals have many types of senses that we just don't share."

Schulten theorizes birds use these additional capabilities to guide them on the proper path, along with visual cues such as the setting sun. Even smell may play a role in how birds are able to memorize the migratory path, that often spans entire continents.

Princeton University researchers Martin Wikelski and Richard Holland conducted a test of their own that appears to support Schulten's theories... and suggests age and experience are also factors. They took 30 migratory sparrows from Washington state, and released them in New Jersey. Younger sparrows flew directly south, as they normally would along the west coast to wintering spots in Mexico. Older birds flew southwest from New Jersey.

"The theory is that they have both a map and a compass," said Holland -- adding the ability to sense subtle changes in magnetism likely guided the older birds along the right path.

Wikelski agrees. "The way that birds orient themselves in nature is probably much simpler than we assume," he said. "They use the one point in their environment that's never changing -- the sunset."

Schulten believes a protein called cryptochrome -- found in the eyes of many animals -- may react to variations in light between magnetic fields, and help guide avians along the proper path. That sense may work in conjunction with the "magnetic compass" theory espoused by the Princeton researchers.

"Birds are very good at picking up little differences in shades that move through their field of vision," Schulten said. "The magnetic field may act like a filter modifying what they see, like a cloud floating in the image."

While other scientists still aren't sure of Schulten's findings, one thing appears crystal clear: humans -- whose brains also contain magnetite crystals, similar to those found in bird cells -- shouldn't plan on being able to magically find their way in a similar manner.

"If we do have a magnetic sense," Holland said, "it's probably weak and not used anymore."

FMI: www.ks.uiuc.edu/~kschulte/, www.princeton.edu/~wikelski/