Homing pigeons use smell to navigate

Washington – A new study has provided evidence that the information pigeons use as a map is in fact available in the atmosphere: odours and winds allow them to find their way home.

Experiments over the past 40 years have shown that homing pigeons get disoriented when their sense of smell is impaired or when they don’t have access to natural winds at their home site.

But many researchers were not convinced that wind-borne odours could provide the map pigeons need to navigate.

Now, Hans Wallraff of the Max Planck Institute for Ornithology in Seewiesen, Germany, has shown that the atmosphere does contain the necessary information to help pigeons find their way home.

In previous research, Wallraff collected air samples at over 90 sites within a 200 km radius around a former pigeon loft near Wurzburg in southern Germany.

The samples revealed that the ratios among certain “volatile organic compounds” (chemicals that can be a source of scents and odours) 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.

These changes in compound ratios translate into changes in perceived smell.

But a pigeon that has never left its loft does not know in what directions what changes occur – unless it has been exposed to winds at its home site.

The findings are published in Biogeosciences, an open access journal of the European Geosciences Union (EGU).