Data confirms that ‘V’ formation helps birds save energy

AP

The next time you see birds flying in a “V” formation, consider this: a new study says they choreograph the flapping of their wings with exquisite precision to help them on their way.

That’s what scientists concluded after tracking a group of large black birds, each equipped with a tiny GPS device recording not only its position but every single wing flap. One expert in animal flight said just gathering that amount of data was a remarkable accomplishment.

Scientists have long suggested that the reason many birds adopt a “V” formation is related to aerodynamics. When a bird flies, it leaves a wake. The idea is that another bird can get a boost from an updraft of air in that wake by flying behind the first bird and off to the side. When a group of birds use this trick, they form a “V.”

While this kind of theory has a long pedigree, it has been difficult to study in the wild.

Researchers from the University of London’s Royal Veterinary College and elsewhere tracked 14 ibises as they migrated between Austria and Italy. The birds had been taught to follow an ultralight aircraft as part of a conservation program.

An analysis of a seven-minute period showed that when the ibises flew in a “V,” they positioned themselves in just the right places to exploit the updraft in another bird’s wake, allowing them to conserve their own energy.

They also appeared to time the flapping of their wings to take full advantage of that updraft, by making a wingtip follow the same undulating path through the air as the wingtip of the bird up ahead.

And when one bird flew directly behind another instead, it appeared to adjust its flapping to reduce the effects of the wake’s downdraft. So birds can either sense or predict the wake left by their flock mates and adjust their flapping accordingly, which is a remarkable ability, the researchers said.

The London scientists reported their results online Wednesday in the journal Nature. It’s the first experimental evidence that birds can adjust their flapping to take advantage of the wake, Florian Muijres and Michael Dickinson, of the University of Washington, wrote in an accompanying commentary.