Homing Pigeons Use 'Mental Map' to Find Their Way Home

A new study of homing pigeons suggests that the birds use a spatial map to find their way home, indicating the birds possess cognitive ability.

Even when released in an unknown territory, homing pigeons are able to find their way back home, a trait that has long fascinated humans, who used the birds to deliver messages centuries ago. It's known that like migratoy birds, homing pigeons determine their flight direction with the help of the Earth's magnetic field, the stars and the position of the Sun. Yet despite extensive research, it has not been fully determined just how the birds are such excellent navigators.

Nicole Blaser, a doctoral student in biology at the University of Zurich, reports on two theories of homing pigeon navigation. The first assumes pigeons "compare the coordinates of their current location with those of the home loft and then systematically reduce the difference between the two until they have brought the two points together."

The second theory suggests that pigeons have cognitive ability through a spatial understanding of their position in space relative to their home loft via a sort of mental map in their brain.

Until now, no clear evidence has been presented to support either theory fully.

For her experiment, Blaser attached GPS trackers to pigeons which had been trained not to eat at their home loft, but rather at a feeding loft about 30 kilometers away.

The pigeons were then brought to a release site unknown to the pigeons in unfamiliar territory. This site was 30 kilometers from the food loft and the home loft, with natural obstacles obscuring visual contact between the release site and the two lofts. Before being released at the unfamiliar location, one group of pigeons were allowed to eat as much as they wanted, while another group was kept hungry.

"With this arrangement we wanted to find out whether the hungry pigeons fly first to the home loft and from there to the food loft or whether they are able to fly directly to the food loft," Blaser said.

The results were telling: hungry pigeons flew directly to the food loft and the fed pigeons flew directly home.

"As we expected, the satiated pigeons flew directly to the home loft, said Hans-Peter Lipp, a neuroanatomist at University of Zurich and Blaser's supervisor for her doctoral thesis. "They already started on course for their loft and only deviated from that course for a short time to make topography-induced detours."

The hungry pigeons took a direct course to the food loft, only deviating from the most direct course to navigate around topographical obstacles.

The outcome led the researchers to conclude that "pigeons can determine their location and their direction of flight relative to the target and can choose between several targets. They thus have a type of cognitive navigational map in their heads and have cognitive capabilities."

Blaser and her colleagues' research is published in the Journal of Experimental Biology.