CORRECTION VIEW TO 76

Of late it struck me like this.

The first flying bird creates partial vacuum during its 3D space.forward flight.2nd line bird travel behing the leader will suffer lack of sufficient air due to formation of partial vacuum.To avoid the risk of falling the successive line of birds have to fly side away from it's preceeders.Then comes the the arrow/v shaped formation-simply to avoid falling down.

Two comments:

1. It's a much more different and difficult question to ask "why do they..." rather than ask "what benefits do they receive from..." The answer to "why" implies knowing the ontological cause for the behavior. There may be answers to the root cause, but for us evaluating the answer is really subjective and not objective. We've got to be philosophically rigorous in our pursuit of knowledge...

2. The benefits the geese receive are based on a wave or draft of faster flowing air that the following geese can get some aerodynamic advantage from. The first goose does three things: (a) it breaks the wind, (b) it pushes a column of air, or maybe a column from each wing, faster to the rear, and (c) accelerates a wave of air to the left and right, and this is the wave of faster air its companions can ride on and get some speed/energy advantage. I be there are also some predator evasion, food finding, and navigation benefits too.

for the view, when driving your car with your mother-in-law honking from the back seat.

For many years I've accepted the theory that the following birds get some form of reduced drag and/or increased lift from the vortices of the leading bird(s).

But nowadays I think we'll never know for sure unless we can follow the V formation with a video camera mounted on a drone aircraft that follows the formation and would allow us to quantify the wing flapping.

If the leading bird(s) demonstrate a higher frequency and/or amplitude of wing motion compared to that of the following bird(s), then I'll be satisfied that the theory is probably correct.

But I'm originally from Missouri.

It's been done, but wing-movement need not correspond directly to energy use - it could simply be a low-energy response to air conditions. In-flight measurement on pelicans using heart rate monitors* is probably more conclusive.

* Weimerskirch H, Martin J, Clerquin Y, Alexandre P, Jiraskova S, 2001. Energy saving in flight formation. Nature 413: 697–698.

They travel in a "V" formation because birds have not declared the flying wedge formation to be fowl!

I was always told that birds, particularly geese who fly long distances, fly in a V formation so that the leading bird effectively works hardest in flight. During the flight each bird will take up the 'lead' position, resting while flying further down the V,each bird creating updraft for the bird behind it.I guess its a bit like long distance runners who run off on the shoulder of the lead runner saving energy (reduced headwind etc)

Don't think many other birds fly in a V other than geese.

OK, what's the catch? I was always taught that it was a matter of aerodynamics. In other words, the lead bird breaks up the resistance of the air enabling the following birds to "coast" along in its wake. Then, when the lead bird got tired, it dropped back to "rest" while another took its place.

Or has that theory been disproved?

Ken Leigh

Lets see if we can put this to bed:

From an excellent site http://www.niquette.com/puzzles/gooses.htm

By flying in a V formation, the whole flock adds 71% greater flying range than if each bird flew alone.

Yes, the 71% additional range is the result of Chinese whisper or other misinterpretation. If probably originated from the relative heart-rate of the non-leading geese being only 71% of the leader's.

But should you place any trust in a web-page whose title doesn't use the proper plural for goose?

To be specific:

The rates of change of parasitic drag and induced drag don't obey complementary laws.

The 50% figure for one-wing-only is used twice when once might be appropriate - especially as the third goose onwards benefit from the efforts of more than one of those in front (again based on pelican heart-rates).

There are two different optima - minimum power, and minimum energy/distance, and minimum energy/distance requires greater speed than minimum power. For migration, energy/distance is the crucial measure - and it may be that a single goose could not continuously achieve this optimum when flying alone.

Having said that, the site is correct that the maximum saving you might expect from the reduction in induced drag is extremely unlikely to be more than 15%. However, you should also expect some reduction in parasitic drag, as the objective of flight is to force air downwards and backwards, but typical wing-powered flight also creates a bit of a bow-wave, and there may be advantage in riding the pressure/velocity gradient. You can also benefit from a reduction in the effect of the self-generated turbulence - except for those at the rear.

Measurements of heart-beat and breathing rates of pelicans suggest that the lead bird is consuming about 40% more energy* than those in the middles of V-sides (positions 3 onwards are roughly equivalent except for the trailing end of the V). While it is possible that some of the excess rates are due to stress, the reduction in actual energy for those at the centre of a side (relative to the leader) is likely to be about 20% - rather than more the 2% proposed. But the goose will still do better of it flies in a larger flock.

*That's similar to the original 71% advantage for being in the middle of a side that was given above. And don't forget that theory suggests that even the lead bird derives some benefit from the formation.

The aerodynamical explanation it's a good one.

But the organisational explanation may be good too.

The V formation implies a leaderchip of one bird (or maybee few more) on the "tip" of the V. The V Structure allows the "directed" bird's in the bodie of the V formation follows in cascade the "movement instruction's" of the leader(s) in a visual way, while they preserve his own spaces of flight maneuvers.

If the bird it's in the left wing of the V formation follows his right front partner bird, and so for the right wing.

Like the acrobatical formation of planes. They sincronise only with his visual partner.

The one in front´s got the map

Actually, your answer only tells the advantage of flying in in V formation. The question was "WHY?" We don't know why. It is hard to discern the motives of birds!

Questions such as "Why do objects fall when you drop them" may not always be answerable, but the answer does not usually require knowledge of motivation. Indeed, if we were talking about humans, the "motive" (why we believe we do things) is often completely different from the true cause of our actions.

Here's a little something that will clarify...and also clear up some ever so slight challenger misunderstandings.

Alaska Science Forum

August 16, 1982

Why Birds Fly in Vees
Article #559

by Larry Gedney

This article is provided as a public service by the Geophysical Institute, University of Alaska Fairbanks, in cooperation with the UAF research community. Larry Gedney is a seismologist at the Institute.

Any day now, the geese, the ducks, the cranes and other transient summer guests will be leaving us to spend the winter in a more sensible climate. One cannot help but feel a little wistful as he watches those majestic vees march across the sky amid the honking and quacking and screeching, and the question always comes to mind: Why do they fly in formation?

When I was a boy, I was told that Papa Duck was always at the head of the vee with the rest of the family spread out behind. Actually, that idea is not much more fanciful than some others that sound a lot more scientific. The favorite incorrect theory is that the lead duck is "breaking trail" for those that follow, in much the same manner that racing cars "draft" in the wind shadow of the leading car. Then, so the story goes, when the leader tires, it drops back in line and another duck takes its place at the head of the vee. That isn't the way it's done.

In actuality, when migrating birds fly in a staggered pattern, each is subjected to the same amount of air friction as its neighbor. The advantage to formation flying lies in what pilots call the "wingtip vortex."

On a downstroke, the air beneath a wing is displaced downward, but in order for the volume of air surrounding the bird to remain the same, some must also be displaced upward. This creates an upwash beyond the wingtip which results in a favorable effect for the bird's neighbor. Each flies in the upwash of neighbors--an effect similar to flying in an upcurrent, with less lifting power needed.

If this is so, it might be asked: Why don't they just fly line abreast, instead of in a vee? The answer is that the line abreast formation does not result in an equal saving of energy for each bird. A study published in Science magazine shows that, for line abreast formations of ten birds or more, those in the center of the formation enjoy about twice the advantage of those at the tips. This is because the center birds are flying in an upwash field generated by neighbors on both sides.

The vee formation balances things out. In a proper vee, each bird is expending the same amount of energy. This even holds for the lead bird, which intuition would tell us receives no help whatsoever from its neighbors because they are behind it. It does though, but if it should happen to move ahead out of the upwash field, it merely drops back until it is in it again.

This applies to any bird in the entire formation. If a member should move ahead of the vee line, it finds that more power is required to keep up with the flight and its speed falls until it is back in line. Thus, the vee is self-stabilizing, and even young birds who have just begun to solo will immediately adjust to any slot in the formation so that it "feels right."

Vees need not necessarily be symmetrical, because only the influence of the neighboring half-dozen birds is significant. The important thing is that the front bird should have others on both sides. In other words, one must always have a vee apex, but the legs can be different lengths. The clever bird, if it understood all this, might think, "Aha! This tells me that, if I flew inside the vee, I would get the benefit of all those dumb clucks around me." Apparently, though, flights do not tolerate malingerers who attempt to use less power at the expense of more work for the main formation. It is possible that exceptions may be made for sick or weaker birds.

The savings in energy brought about by formation flying can be truly significant. The study in Science reports that a flight of 25 birds can achieve a 70 percent range increase over a bird flying solo using the same amount of energy.

At the same time, it is interesting that formation flights cruise at an economical speed 24 percent less than the single bird who is, possibly, frantically trying to catch up with the main formation.

Looks like NASA is considering this to save fuel:

http://www.theregister.co.uk/2009/05/19/darpa_goose_v_formation_ploy/

These posts all sound very good. But none explain why they fly in a single V formation. Most explanations would allow us to see multi-V formations with branches or very unbalanced V forms. Geese fly over our house all of the time and they seem a little more organized than this.

Are we sure they're just not sending a "vat" signal?

Are these geese vane geese?
This is the vane goose that flies with the flock that John piloted.
This is the rocket that powered the space-ship that carried the vane goose that flies with the flock that John piloted.
This is the roast goose that sat in the rocket that powered the space ship that crashed into the sun and carried the vane goose that flew with the flock that John piloted.
...

If you observe a flock for an extended period of time you will be see that the birds take turns to lead the flock!

If the flock is flying, how do you do this?