Jan 18 2013

Why We Fly in V Formation

Published by at 7:20 am under Bird Behavior,Tenth Page

Why do swans, geese, and ducks fly in V formation?

Because it makes their journey easier.

Everything that flies experiences turbulence that slows it down.  Some of the turbulence is created by the act of flying.  For instance, during lift cones of swirling air called vortices roll off the wingtips and induce drag.

Here’s a dramatic NASA photo of a wingtip vortex, enhanced by red smoke.

 

The right and left wing vortices swirl in opposite directions — the left spins clockwise, the right counter-clockwise — resulting in two trailing swirls behind the airplane or bird.  Click here and here for videos.

The induced drag is especially hard on large or heavy birds (swans and geese) and birds with small wings relative to their size (ducks) so these birds line up in Vs to reduce the turbulence.

Here’s how it works.

In the photo below, four tundra swans are flying in the direction of the blue arrow.  Behind the leader, the blue lines show that each bird has its right wingtip in line with the left wingtip of the bird ahead of it.

 

Now I’ll draw the vortices and their spinning directions using blue for the left wing, red for the right wing.  Blue/left spins clockwise.  Red/right spins counter-clockwise.

When the blue vortex meets the red vortex at the wingtip, they cancel each other out.   By lining up in this fashion, each bird has one wing that experiences less turbulence.  That makes it easier to fly.

The lead bird is out there alone, though.  He’s the only one who gets no assistance so he tires before the rest of the flock.  The flock solves this by changing leaders when the first one needs to rest.  The lead bird drops back into the V and another bird takes his place.

Long, long ago birds solved the problem of wingtip turbulence.  When we invented airplanes we found out what it was all about.

 

(Credits:
Photo of tundra swans in blue sky by Chuck Tague.  Line of tundra swans by Marcy Cunkelman.  Red vortex photo by NASA via Wikimedia Commons; click on the image to see the original.
Today’s Tenth Page is inspired by a diagram on page 123 of Ornithology by Frank B. Gill.
)

7 responses so far

7 Responses to “Why We Fly in V Formation”

  1. aristarkhoson 18 Jan 2013 at 7:41 am

    Thanks for the technical explanation. My question is why the V usually has a longer line on side than the other. Like a large tick mark. I am not sure if it a usual formation, ot is something I noticed while watching parts of a documentary called Winged Migration.

  2. Kate St. Johnon 18 Jan 2013 at 8:12 am

    I have a theory about one longer side than the other: If it’s a very large flock the width of the V would be too great to be practical. …But who knows?

  3. George Bercikon 18 Jan 2013 at 11:33 am

    Someone needs to explain this to the Sandhill Cranes.

  4. Kate St. Johnon 03 Feb 2013 at 3:52 pm

    Wow! David. That’s really cool! The book didn’t mention the pressure wave so this adds a whole new aspect. … I have seen the V’s break up the way you describe. Very cool.

  5. Kate St. Johnon 15 Jan 2014 at 4:30 pm

    New research as of January 2014, published in USA Today

  6. Carolynon 07 Jun 2014 at 5:06 pm

    I was very puzzled to find a flock of a dozen or so geese passing over my neighborhood this morning…in V-formation. Do geese ever fly this way when they are not migrating? I thought that these birds would have separated two-by-two months ago, and be busy now, raising their individual broods. Could this flock be from the still thawing Great Lakes? Possibly yearling birds who haven’t found mates yet?

  7. Kate St. Johnon 07 Jun 2014 at 6:48 pm

    Carolyn, Canada geese don’t breed until they are two years old so the group you saw may have been the “teenagers.” They will fly in formation when they’re moving to different feeding areas because the V formation is more efficient (as the article describes).

Comments RSS

Leave a Reply

Bird Stories from OnQ