Putting GPS To Work, Researchers Shed Light On
Road-following By Pigeons
Using satellite tracking to study the paths pigeons take on homeward-bound
journeys, researchers have obtained strong new evidence to support a long-held
theory: in some environments, pigeons instinctively learn to follow major
roadways in navigating their flight. The new findings are reported by a
research group headed by Dr. Hans-Peter Lipp of the University
Anecdotal evidence from breeders of
racing pigeons as well as initial aerial tracking studies together suggested
that pigeons may follow roadways and use highway landmarks as turning points in
their flight. However, the challenge of accurately tracking the birds stood in
the way of solid quantitative analysis. In the new work, miniaturized GPS
"flight-loggers," which pigeons carried on their backs, allowed
researchers a clear and reliable picture of the birds' flight paths.
Over three years, the researchers analyzed more than 200 flight paths of
20-80 km in length made by pigeons travelling toward
their home loft from numerous release sites located in the general vicinity of
Rome, Italy. They found that, when released from familiar sites, pigeons with
homing experience were significantly attracted to highways and a railway track
running in the approximate directions home. When these structures began to veer
significantly from the beeline to the loft, some birds tended to break away and
head in a more homeward direction, but others took a detour by following the
highway until a main junction, at which point they followed a valley road in
the direction of the loft.
Overall, the degree to which the birds appeared to follow roadways was
strongest in the early and middle sections of their homeward journeys, when,
the researchers suspect, roads serve to stabilize the birds' innate compass
course. As they approached the loft, the birds appeared to switch strategies
and rely more on topographical points as bona fide "road
map" components. The birds may use these features in a cognitive strategy
that helps them locate their loft in their more immediate home area.
The researchers found that, although following roadways in some cases
represented significant digressions from the beeline home,
in general the early benefit of the roadways in keeping the birds on course
seemed to compensate for the added flight distance. In fact, the birds appeared
to prefer to follow roadways once they became experienced with the release
sites; individuals who made three or more journeys home showed an increasing
tendency to follow highways. The authors speculate that the preference for
roadway following could form because easier navigation may allow brain
processing-time and power to be directed to other tasks, such as watching for
The pigeons appeared to be attracted to the SS Aurelia, Italy's
old coastal highway, to a greater extent than the newer and larger highway A12
or the railway. The SS Aurelia traces the ancient imperial Via Aurelia, which
was begun in 241 BC and connected Rome
to what is now southern France.
It is unclear the extent to which pigeons or other birds may employ
strategies akin to road following in non-urban areas, but the authors point out
their agreement with previous assertions that homing pigeons appear to have
"a remarkable ability to shift from one homing strategy to another,"
and they urge that their new findings be reasonably interpreted.
Hans-Peter Lipp, Alexei L. Vyssotski,
David P. Wolfer, Sophie Renaudineau,
Maria Savini, Gerhard Tröster,
and Giacomo Dell'Omo:
"Pigeon Homing along Highways and Exits"