Homing Pigeons Follow Their Noses
November 6, 2013

Homing Pigeons Follow Their Noses Home

Lee Rannals for redOrbit.com - Your Universe Online

A scientist writing in the journal Biogeosciences suggests that homing pigeons may using their noses to help guide them back home. Birds are known to use tools like the sun and Earth’s magnetic field to help them navigate around. Homing pigeons are king of this category and were even used by spies in World War II to help deliver messages in and out of war zones. However, the skill homing pigeons possess to help navigate the skies has been a subject of debate.

Studies have shown for the past 40 years that homing pigeons can get disoriented when their sense of smell is impaired or when they don’t have access to natural winds at their home site. Many scientists did not believe that wind-borne odors could provide the map pigeons need, but new research shows that the atmosphere actually does contain the necessary data to help the birds find their way back home.

Hans Wallraff of the Max Planck Institute for Ornithology in Seewiesen, Germany collected air samples at over 90 sites around a former pigeon loft near the city of Würzburg in southern Germany. These samples revealed that the ratios among certain volatile organic compounds in the atmosphere increase or decrease along specific directions.

“For instance, the percentage of compound A in the sum A+B or A+B+C+D increases the farther one moves from north to south,” Wallraff said. “If the percentage of compound A increases with southerly winds, a pigeon living in a loft in Würzburg learns this wind-correlated increase. If released at a site some 100 km south of home, the bird smells that the ratio of compound A is above what it is on average at its loft and flies north.”

For example, a person in Munich may smell an Alpine breeze when there is wind blowing from the south. If that person is displaced near the mountains, he or she could detect a strong Alpine scent and remember that smell is associated with southerly winds. While this example shows how the association works, Wallraff still needed to show that the atmosphere carries the basis of the internal map system pigeons need to navigate.

The researcher developed a model showing that “virtual pigeons” with only knowledge of winds and odors at home could theoretically find their way back to lofts using real atmospheric data.

“My virtual pigeons served as tools to select those volatile compounds whose spatial distributions, combined with variations dependent on wind direction, were most suitable for homeward navigation,” Wallraff said in a press release.

His model uses an iterative approach to imitate animal evolution by introducing random mutations in the virtual pigeons. The model makes the pigeons most sensitive to those volatile compounds that are most effective for navigation. It helps create pigeons capable of finding their bearings as well as shows that even inexperienced birds could use atmospheric information for navigation.

“Work with real pigeons was the beginning of the story. In this research, I wanted to find out whether and in what way the chemical atmosphere fulfills the demands for avian navigation. Eventually, to identify the chemical compounds birds actually use for home-finding, we will need real birds again. But this is far in the future,” Wallraff said.