When geese migrate south for winter, they don't just fly for fun — they're working together to save energy. A team of researchers from Brown University in Rhode Island has just figured out exactly how birds in a V-shaped formation make their flights easier, and the answer is simpler than you might think: they barely flap their wings.
The scientists studied northern bald ibises — distinctive birds with bald, orange heads — and built a computer model to understand what happens when one bird flies behind another. When a bird positions itself in the "sweet spot" of a V-formation (behind and slightly to the side of the bird ahead), it gets a surprising boost. The new research shows these followers use 11% less power to stay airborne. That's like walking instead of jogging for a whole day.
So how does it work? The secret lies in the tiny horizontal tornadoes that spin off from wingtips — scientists call them wingtip vortices. As a bird's wings push through the air, these little spinning columns of air create what researchers describe as an "upwash zone" on either side. A trailing bird can essentially ride this invisible wave of rising air, which means it doesn't have to work as hard to fight gravity and move forward.
"The big change we see in this position is in the amplitude of flapping," said Olivia Pomerenk, a postdoctoral researcher at Brown who led the study. "We're looking at an amplitude that is something like 70% of what it would be if the bird were flying alone. That's a pretty dramatic change."
The researchers built their model frame by frame, using real data about how ibises flap their wings. By breaking down each moment of a wingbeat, they could see exactly how the undulating wake from a leading bird affects the one following behind. The key discovery: the upwash from the lead bird reduces how much thrust a follower needs to generate. With less thrust required, the trailing bird can slow its wingbeats significantly.
This isn't entirely new territory for Brown's flight research lab. A few years ago, experiments with starlings in their custom wind tunnel — equipped with high-speed cameras — had already shown that V-formations help birds save energy. That earlier work found birds could reduce their energetic cost of flight by 25% under wind tunnel conditions.
But the new model goes further by explaining the "why" behind these savings, which has real-world applications beyond just understanding nature.
"There are also implications for engineered systems," said Professor Kenny Breuer, who runs the lab. "All of this can also be applied to understanding how to best operate swarms of drones used in agriculture or firefighting."
Pomerenk says she hopes to eventually expand the model to include how birds communicate and make decisions as a group — a first step toward understanding the breathtaking coordinated swarms, called murmurations, that sometimes light up evening skies.