V formation in flying birds maximizes aerodynamics: study
Northern Bald Ibises (Geronticus eremita) flying in formation next to a microlight.
Credit: Markus Unsöld
For 14 northern bald ibises flying in a V formation from Austria to Italy over the course of several weeks in 2010, the migration itself was an achievement.
Northern bald ibises are almost extinct, and the birds had been hand-raised in zoos as part of a unique program to reintroduce them into the wild. They had been taught to follow a paraplane that would hopefully train them to make the yearly trip on their own. It was the seventh such group of Ibises to make the paraplane-led trip.
But this group was special. They were wearing ultra-light sensors on their backs that logged highly accurate GPS and speed data, and every wing flap was being monitored by biomechanics researchers from the U.K.'s Royal Veterinary College.
Scientists peering into the sky have long suspected that birds fly in a V formation to minimize energy expenditure on the animals during long flights.
But this group of Ibises offered an unprecedented opportunity to test that during actual flight. Because they were handraised, it was possible for the veterinary college researchers to attach their sensors to the ibses with harnesses.
The team, led by Steve Portugal, discovered that the theories held true. By analyzing the best seven minutes of data from 43 minutes overall -- 180,000 wing flaps -- they found that the ibises did position themselves in a way the maximized their capture of upwash from the birds in front of them, making the ride easier.
But what surprised them was the degree to which the birds managed to do this. The ibises didn't find themselves in the right position just by accident -- the loggers showed that the birds hit the sweet spot about two-thirds of the time, meaning they are much better at exploiting the flight pattern than previously thought.
"It's like they've been programmed and the bird in front has texted its coordinates to the one behind and said, plug these in and follow my path through the sky. That's why it's such an achievement." says Portugal. "We're not entirely sure how they do it."
"The idea that every step of the way they may be doing something clever was a surprise to us," says Jim Usherwood, another author.
"They're using a level of subtlety we didn't think they were going to be able to do."
Scientists not involved in the study called it:
“It’s not an unexpected finding, but this documents it in a more convincing way, and I think it shows with more sophisticated techniques that we can go to the field and quantify animal performance with greater resolution and accuracy than has been done in the past,” said Andrew Biewener, a mammalian and avian biomechanics expert at Harvard University's Concord Field Station.
The study is published in this week's issue of Nature, and the folks at the journal have put together this video about the study:
Kate Allen is the Star's science and technology reporter. Find her on Twitter at @katecallen.