goose migration - formation and cooperation

A sign from fate! I was all set to ask if the lead birds in the famous migrating V shape took turns (see fact 3 below), and then today I was sent the following list of “facts”, and each fact was followed by some moral lesson. I removed the moral lessons, but what’s the Straight Dope on these “facts”?

[list=1][li]As each bird flaps its wings, it creates an uplift for the bird following it. By flying in a V-formation, the whole flock adds 71% greater flying range than if it flew alone. That’s a fact. Seventy-one percent greater flying range than if each bird flew alone.[/li][li]Whenever a goose falls out of formation, it suddenly feels the drag and resistance of trying to fly alone and quickly gets back into formation to take advantage of the lifting power of the bird immediately in front.[/li][li]When the lead goose gets tired, it rotates back into the formation and another goose flies at the point position.[/li][li]The geese in a formation honk from behind to encourage those in front to keep up their speed.[/li]When a goose gets sick, or wounded, or shot down, two geese drop out of formation and follow it down to help and protect it. They stay with it until it is either able to fly again or dies. Then they launch out on their own with another formation or catch up with the flock.[/list=1]

I imagine you are looking for published sources, but I can address 4 and 5 from experience as a long time hunter. On #4, geese are very verbose and you can tell different individuals by sound. As they fly in formation, they all talk, from any point in the formation. Often, they are calling to other formations or geese on the ground/lake. I believe they are looking for information on available food (as in, is that cornfield picked over yet; the feeding geese give a different call than a flying goose looking around) or a suitably safe place to hang out for the day.

For #5, that is complete nonsense. A goose whose mate has been wounded will sometimes follow the injured mate down, but is just as likely to continue flying, particularly if something on the ground looks dangerous to it.

On #3, it’s frequently not so much that a tired leader “rotates back”, but that it slows a bit and another, usually adjacent, goose takes point merely by maintaining its own speed and position. In other words, the formation shifts, not the geese in the formation.

That didn’t take me along.

I asked my buddy the former Marine pilot. There is no benefit aerodynamically to flying in a V. There is a benefit to flying immediately behind, but not behind and alongside.

The point of flying behind and alongside is specifically to avoid turbulence, and to maintain visibility.

Arguably, the flapping of wings creates a slight downdraft. The geese are pushing air down to maintain their altitude. Geese behind the lead geese would be encountering a slight downdraft actually creating more work.

#1 is therefore false.

As for the rest, I think they’re incorrect as well. Flocking is like schooling in fish. It’s an emergent instinctual behavior rather than overt cooperation.

For example geese fly in that formation because it’s safer to travel in numbers, and to avoid collisions.

So, an individual goose’s behavior, programmed into it’s nine volt brain, is to

  1. Fly with other geese.
  2. Fly close.
  3. But not to close
  4. Maintain visibility
  5. Head south

Those rules, are preprogrammed tendencies create the v formation. But a given goose is just as content in any particular place of that formation.

I know that’s the way that it works for a lot of flocking birds. There may be something special about Geese or ducks, but I haven’t heard about it.

#1: This is a subject of some controversy among gooseologists. This is obviously something that is rather difficult to measure directly. There have been some analyses using aerodynamic modelling that have suggested there is a significant benefit of this kind from formation flying for large birds. Other researchers say that the birds do not fly at the optimal distance from one another to take full advantage of the effect. AFAIK, the consensus is that there is at least some energetic benefit from flying in formation, though the exact figure is not well established. (However, the “71%” seems rather high to me.)

#2. Possibly true.

#3. Probably true to some extent. The same goose certainly does not lead all the time; however, dominant individuals may spend a disproportionate time in the lead. I don’t think it’s well established the just how the trading-off of the lead is handled. Again, a difficult question to study.

#4. Geese honk in order to maintain contact with each other, and in order to know where other individuals or flocks are. I’m not aware that the ones behind honk any more than the ones in front.

#5. I agree with cards.

Scylla, you can’t extrapolate from fixed-wing aircraft to bird flight in this case. The birds are taking advantage not of turbulence per se, but of vortices shed off the wing tips.

This site discusses testing various hypotheses on the subject. The authors have found that there should be significant advantages for a large species of goose, much less for a smaller species.

This site mentions how traditionally pilots have tried to avoid the vortices produced by other aircraft. However, NASA is now studying how how jets can exploit the vortices in V-formations in order to fly farther on the same fuel.

Here’s something on research on pelicans that has provided the first empirical confirmation of the benefit of formation flying, originally published in Nature. The numbers for pelicans indicate a 14% advantage for formation flying.

Thank you fellows. My conclusions:
#1 Grossly exaggerated (Pelicans 14% advantage would seem to me to indicate that geese can’t attain 71%)
#2 Possible
#3 Poorly stated
#4 Unknown
#5 false

Since the e-mail came from one of my superiors at work, I suppose it would be foolish to e-mail him back with the information that his “facts” were a bunch of bull-hockey.

Why would a bird want to be at the front of the pack anyway? A lot more stress that way. I think third or fourth in line is more restful, and when you arrive, you can push the tired old leader out of the way and pick the best nesting spot for yourself.

I agree with Scylla The lead plane in a formation always uses less fuel that the others. The leader just sets his throttle and course and flies. In order for the followers to stay in close formation, constant small corrections to attitude and throttle have to be made. These small maneuvers create increased drag and use up energy, thus more fuel is consumed. So the bird trying to stay with the leader, especially the one at the tail end of the V, will use more effort than does the leader.

The “aerodynamic assist” idea is further weakened by the fact that many, in fact most, long distance migrators such as the Arctic Tern don’t fly in V’s.

I live along the eastern Canada Goose flyway and have observed in the Autumn local gull populations imitating the V-formation. I presume they picked this up from the geese who are in the neighbourhood at that time. It is definitely a V-formation, not just a moment of accidental acuteness and I have seen it more than once. If there is any benefit to it though, it is soon forgotten as the behaviour does not last into winter.

This makes me think either gulls are collectively smart but have short memories, or they are conformists.

Not to add anything of substance to the thread, but I once fell for the following.

Q: Do you know why one side of the V in a flock of flying geese is always longer than the other?
Me: No, why is that?
A: Because there are more geese on that side.

This article from the Anchorage Daily News echoes the “71% greater range” figure, stating it comes from an “often cited study”. They don’t mention the particular study, however.

Doing some checking, I found that the study in question is: Shollenberger, C. A., and Lissaman, P., “Formation Flight of Birds,” Science, May 1970.

I couldn’t locate a copy of that paper, but I did find this pdf document (“Optimum Spanloads in Formation Flight”), which references that paper:

This should be a reasonable facsimile of what Arnold received.
This article from Alaska Science Forum supports #1 on the list

(refers to the Science article Darwin’s Finch cited.)

So, I think
#1 true
#2 true
#3 false
#4 possibly
#5 false.

There are both "aerodynamic"and “behavioural” explanations for V-shaped flight. Both have been mentioned above and both are true.

Aerodynamic benefits - Taking advantage of wingtip vortices of the bird in front is supposed to reduce drag and thus reduce energy outlay http://www.dfrc.nasa.gov/PAO/PressReleases/2001/01-61.html
This may work for aircraft however, when the birds flap their wings the vortices are more complex and the benefit not as pronounced. When the birds are gliding this is where the benefit would be felt.

From New Scientist, issue 2338: "Experiments reported in Science in 1970 by P. Lissaman and C. Shollenberg (vol 168, p 1003) showed that geese flying in a V can travel 70 per cent further than solo birds. " (The oft cited study. Aside - seems strange to quote 71% above - this is very precise value for a relatively imprecise type of study.)

Behavioural benefits - Geese have eyes set such that they have good all round vision but have a blind spot directly in front. If the geese flew along side each other in a line there would be no constant direction. A leader is followed to save energy that would otherwise be expended in jostling for direction and breaking away. The V formation allows the signal of direction to be fed efficiently down the line from the leader, without the bird having to turn its head.

Put your hand in front of your face between your eyes. If you were following someone in front of you and you couldnt turn your head, then where would you rather line them up so that you could easily follow? Just to the left or right of your blind-spot, right.

So it seems both are true. These two benefits co-evolved.

As I said before, one can’t extrapolate directly from fixed-wing craft to birds. I would suggest you read the article I linked to in my second post, regarding possible benefits to aircraft of flying in tight formation.

I agree that for aircraft the benefits of close formation flying under manual control are outweighed by the drawbacks. However, you need to consider that:

  1. The vortices produced by fixed-wing craft are going to differ from those produced by flapping feathered wings.

  2. Bird flight is usually at much lower speeds than human fixed wing craft.

  3. As a corollary to 2, it’s easier for birds to adjust their position.

  4. Although even a slight contact between aircraft can have disastrous consequences, this is not true for birds. Therefore the birds don’t have to be nearly as careful in adjusting their positions.

I suggest you read the link in my first post. The advantage in formation flying is correlated with the size of the bird. Many, probably most large flocking birds that use flapping flight fly in formation at least some of the time, including geese, swans, storks, pelicans, cormorants, and others. (Many of these specie are unrelated.) There is little if any energetic benefit for smaller species (like terns), so they do not fly in formation. This last point in fact argues in favor of the energy efficiency hypothesis for formation flying as opposed to the orientation one, since orientation benefits would apply equally well for smaller species.

My own evaluation of the five questions of the OP are:

#1 - True in principle, but exaggerated (the figure is based on information published more than 30 years ago; recent empirical studies suggest a lower figure)
#2 - Possibly true, but unconfirmed
#3 - True, sort of
#4 - False
#5 - False

I am addressing here only the observed behaviors, not the supposed “motivations” of the bird.

What is wrong here is to assign any altruism to the birds with respect to their behaviors. These behaviors can be understood in terms of benefit to the individual - it is unnecessary to postulate any benefit to the group as a whole to explain them.

Argh! moes lotion beat me to it! I fell for that once too. I love stupid jokes like that!

I might mention that even for large birds the energetic benefits of formation flying apply only to flapping flight (which may be interspersed with periods of gliding) They do not apply to soaring flight (which depends on the used of thermals). Large birds which depend primarily on soaring flight (e,g. vultures, hawks, etc.) do not fly in formation.

…And on a religious note. I attended a funeral for a good friend some years ago, and the pastor, during his eulogy, likened the passing overhead of a flock of geese, as friends taking a departed friend home to heaven. Needless to say, thats the thought that comes to me with every sighting of a flock. I look up and smile.

I suppose it would be foolish to fight ignorance at every turn. :smiley: