No, the F-18 would exhibit much stronger vortices at low speed.
(Someone shoulda posted that F-18 link sooner!)
It would be bullheaded to deny it is possible that birds fly in V formation for the energy saving. Of course this would mean that either there was a genetic predisposition to the V flock, or some bird long ago stumbled across it and it was enough of an advantage that that birds genes eventually dominated the population.
A bird that was able to figure out that it was using less energy to fly in a V would be a pretty smart bird. I would think it would have to fly in formation for a while and see how tired it gets as compared to flying the same length of time not in formation. That seems so far out that I would put my money on the V being genetic. In that case geese wouldn’t fly in formation because it saves energy. The energy saving, if any, would be a side effect of which the bird is unaware.
As Xema has already mentioned, smaller birds don’t often fly in formation. Because of scaling effects, larger and heavier birds are closer to the limits for flight, and getting additional lift is much more important for them.
Did you read the article I linked to in my second post? As I’ve already mentioned, birds are not drafting in the same way that a cyclist or car drafts. Instead, the birds rely on updrafts from wingtip vortices rather than a low pressure area behind the leading bird.
If the links I have already provided haven’t convinced you, you may need to consult the technical literature for a more complete discussion. The following article has some detailed information on various factors affecting energy saving in formation flying, as well as extensive references:
Not at all. Birds are keenly aware of variations in air pressure and the location of air currents. They have an extremely sensitive pressure sense and can detect very small variations. It would be the simplest thing in the world for a bird to detect that there was an updraft behind a leading bird and make use of it to make its own flight easier. It would be able to tell this instantly, and wouldn’t need to do it over a period of time. Similarly a human can easily tell the difference between swimming with the current and swimming against it.
Yeah. I tried to get in a post saying to forget the arctic tern. Different critters have different solutions.
But the Board decided to be cranky and I got the “this url unvavailable” message.
This is the part that seems odd to me. If the trailing bird gets 10% of the energy for its flight from the wake, that energy has to come from the lead bird. If the energy recovery is 50% then 20% of the flight energy of the lead bird is wasted, for its benefit, in the wing tip vortice on just one wing.
And finally, it actually makes no real difference whether or not I am convinced. I think I’ll just take in all the information and withold final judgement. The birds will either fly in a V to save energy or they will do it because they are programmed that way and would do so even if they didn’t migrate.
In any case, thanks for the straight dope on flocks of birds and what happens during their group flight.
You’re right - a meaningful amount of the energy required for flight is “wasted” producing the wingtip vortices. It’s an inescapable effect (though it can be minimized by long & narrow wings, such as sailplanes & albatrosses have).
But the V formation allows the trailing geese to use some of the energy that would otherwise be wasted stirring up the air. There’s no penalty to the lead goose, and all the others have a bit less work to do. As Colibri’s link said, the geese swap the lead, so each goose spends most of its time in a lower-drag position.
For analogous behavior, consider how porpoises ride a bow wave or how gulls ride the air displaced by bluff-bowed ships. These behaviors didn’t take evolutionary time to appear.
That’s a good article, but I’m curious/confused about this bit:
How does that (the graped section) actually work? Once the vortices are created, how does dissipating them propagate forward as benefit to the bird that created them?
If it’s intuitively obvious, it doesn’t need an explanation. [/semantic nitpick]
Just a quick note on theF/A-18 tests referenced earlier. From the picture in the link, it’s clear that the tests were not conducted with the trailing aircraft in a V formation. Rather, the plane was further back and more behind so as to be in the vortex from the wingtip.
In addition there is the following:
The tests were conducted as part of the design of an autopilot to allow flying in the vortex continuously which a pilot would have difficulty doing for long periods of time.
So, even if the fuel saving effect is conceded, it doesn’t seem to have much bearing on birds in their V formation. The planes weren’t in the V, and birds don’t have autopilots but themselves must compensate for the vagaries of the airflow for long perriods.
As to the lowered heart rate of the pelicans I don’t think that’s a very well controlled experiment. Maybe flying alone creates anxiety in the penguin because of increased vulnerability to predators while flying with others calms them. 
Unfortunately most of the original references cited in the article I linked to are not available on-line or else require a subscription. But the fact that flying in formation saves energy, both for birds and airplanes, has been pretty well-established scientifically.
David, if you really want to understand the evidence on the subject I would suggest once again that you need to consult the technical literature on it, rather than nit-picking the rather sketchy material that is available on-line.
I have no doubt that penguins would experience considerable anxiety in flight, whether alone or in flocks. 
Having flown in formation with lighter, slower piston engined aircraft, I can attest to Davids statement about the difficulty of staying in the proper spot and since that seems to be a non standard point aft and to the side, holding that place will be unusually hard and the use of a special auto-pilot function will be necessary, Especially if the strings are more than a lead plane and one trail. The amount of effort to hold position as the string adds planes is by the square. Get a 7 plane echelon going and tail end Charlie is fighting hard to hold some sort of position.
Heavy, high speed jets are much easier to fly formation with in the amount of throttle movement and control movement required. No less in concentration, it is all very tough flying, but the excursions from steady flight are much less in a F-18 than in P-47 or a Pitts Special.
Here’s another photo that includes wingtip smoke and shows the relative positions. I think this qualifies as a V formation (even though, strictly speaking, it would take a minimum of 3 aircraft to make a true ‘V’). Due to the speeds involved, the angle is different from what geese use. But the principle is just as you indicate - to fly in the favorable part of the vortex.
Quite right - it’s something they are exceedingly good at.
Think of the complexity of the “autopilot” that would be needed to keep a bipedal robot walking upright over uneven ground. Then consider that you can do this for hours while hardly giving it a thought.
It seems to me that a large flock could face the possibility of splitting in half if birds at, say, the left side want to go a different direction than the birds on the other side of the flock (on the right side). Wouldn’t this be possible if there are no leaders for more than a couple seconds and the flock, as a whole, has to retain the potential to suddenly change directions on a whim?
I’m sure there’s an answer, but it’s probably a little too technical for my tastes…
That happens; see this video of flocks of starlings interacting.
What I was mostly discussing in my Staff Report was the situation in which a flock is trying to evade a predator. In this situation, neither individual birds nor the flock as a whole “wants” to go in any particular direction for very long. The prime concern for an individual bird is to stay with the flock, so it won’t be picked off. In this situation, it is unlikely that the flock will split (although it can happen). Birds that veer towards the main part of the flock are followed by others; those that veer away are not.
I also mentioned the situation when a flock mills around a bit before taking off in one direction after a “consensus” develops. In this situation it would be more possible for a flock to split, if birds that want to go in different directions gravitate to different parts of the flock. Even so, flock cohesiveness may be difficult to override.