Northern bald ibises flying in formation.
BI Answers: Why do birds fly in a V?
Scientists have long held that birds fly in a V-formation to save energy. But it was only recently revealed how and why birds benefit from this trick.
Migratory birds flying in a “V” shape flap their wings at precise times to take advantage of the lifting power generated by the bird in front, British researchers, led by Steven Portugal at the Royal Veterinary College in London, reported earlier this year in Nature.
The study took advantage of new sensors that tracked the movements of 14 northern bald ibises during a portion of their migratory flight from Austria to Italy. This was the first time that data had been recorded from birds flying in the wild.
When a bird flaps its wings, it creates lift by generating a looping motion of air around the wing.
The airflow blowing over the top of the wing is thrown downward, known as downwash (shown in red in the graphic below), while the air at the wing’s tips is accelerated upwards, known as upwash (shown in blue).
The birds want to be in the region of upward-moving air to reduce the effort needed to fly.
Birds not only position themselves in the best possible spots to take advantage of the upward flow of air. They are also paying attention to the timing of the flap movements of the bird ahead, “which create tip vortices that undulate up and down,” Florian Muijres and Michael Dickinson wrote in a News & Views commentary on the study, also published in Nature.
A bird will alter the timing of its wing beat to stay in the upwash created by the moving wingtips of the bird ahead of it.
“A bird that is following another bird must carefully adjust its own flapping motion, not in perfect temporal synchrony with the leader, but rather at a precise phase lag that tracks the tip as it oscillates,” Muijres and Dickinson write.
To do all those things, the best way for the birds to fly is in a V- shape.
Check out the video below for more on why birds fly in a V-formation.
This post is part of a continuing series that answers all of your “why” questions related to science. Have your own question? Email [email protected] with the subject line “Q&A”; tweet your question to @BI_Science; or post to our Facebook page.
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