The Pelican Experiment
Science Offers Proof That Flying in V-Formation Boosts Efficiency
Listen to David Kestenbaum's report for All Things Considered
Great white pelicans flying over the Senegal River. They have heart rate monitors attached under the feathers on their back.
Photo: Henri Weimerskirch
Oct. 17, 2001 -- The idea that birds can save energy during migration by flying in a V-formation has been around for decades, but no one had the empirical evidence to back up that claim until now. NPR's David Kestenbaum reports how a group of scientists, with the help of great white pelicans in Senegal, finally proved what many people have been theorizing for years.
Henri Weimerskirch of the French National Center for Scientific Research and his colleagues began their project by implanting heart rate monitors under the feathers of eight trained pelicans. The scientists then closely observed the birds' heart rhythms and their flying habits over the Senegal River.
Weimerskirch and his team confirmed what they suspected all along -- when the pelicans fly in group formations, they spend considerably less energy and get more mileage out of their food sources. The data shows that pelican heart rates usually decrease by more than 10 percentage points and the birds also appear to beat their wings less frequently and glide for longer periods when they fly as a group.
The scientists reported their findings in this week's edition of the journal Nature. In the article, they write that the formation flight offers a significant aerodynamic advantage, adding that when the pelicans' energy expenditures are calculated from heart rates and frequencies of wing movements, the numbers indicate it is about 14 percent more efficient for pelicans to fly in formation than to take on a solo flight.
This conclusion makes plenty of mathematical sense, says Jeremy Rayner from the University of Leeds, who studies the science of flight. "A trailing bird can fit outside the wake of the bird in front, sitting in a passage of rising air," he explains. "When the air is rising, it can fly with slightly less energy. We know this works in aircrafts flying in a V-formation."
Weimerskirch thinks that there are some behavioral benefits, such as increasing foraging range, to joining a structured flight group, and that could help explain why these birds began flocking in the first place. "Pelicans use such flight patterns extensively," he writes. "Not only during migration but also during group commuting trips between colonies and foraging zones."
Read about the evolution of flight, from the early gliding vertebrates to modern birds.
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