Why do birds fly in a V formation?

May 12, 2019 • 2:45 pm

Reader Jim called my attention to a video made by Nature addressing the time-old question, “Why do many birds fly in a V formation?” The conventional answer is based on energetic benefits: the birds following the leader draft on the birds before them, thus saving energy. You can imagine how hard this question is to answer.

Well, watch this wonderful video to see if the answer is correct, at least in one species. I won’t give away the answer, but the hypothesis makes a cool prediction that can be tested.

. . . and here’s the paper on which the conclusions are based (click on the screenshot to read it):

44 thoughts on “Why do birds fly in a V formation?”

  2. Makes sense to me. Getting the benefit of the air movement produced by the wing in front of you. Also flying in slot formation to avoid turbulence while getting this benefit. This is the only way the entire flock or group stays in contact with the leader as well. They do not have IFR (instrument flight rules), GPS or auto pilot on board.

    1. OK.
      So, why don’t insects fly in V-formation?
      Or, do they and I don’t know about it?

      1. Not all birds fly in v formation either. It tends to be mid to large sized birds that do it. That may suggest that below a certain size the turbulence effect is too small to make a difference or it may be that for birds that prefer to fly in a swarm there are other selection pressures that outweigh any energetic benefit from v-flying.

        1. Further to the above, some very large birds don’t do it either. Many large birds of prey and other large birds such as storks migrate in groups but do not form v-shaped flocks. These birds do not progress through flapping flight however, but instead exploit thermals to soar upwards to great height and then glide down to the base of the next thermal. Because they are largely relying on air convection to power their flight there is no energetic benefit to be gained from v-formation flying for these birds and they don’t do it!

        2. Was there ever a behaviorial characteristic that was as simple as it looked at first glance?

  6. I’m surprised this was still a question. I lived under the illusion that it was already well established that the V formation was due to taking aerodynamic advantage, and that the precise mechanisms were well known.
    How wrong can one be! Very interesting video.

    [It is different from the zebra stripes though: if the V was not established, it was clearly expected, while the fly explanation of zebra stripes was a lightening bolt].

    1. Sensor technology is extremely good these days. I remember hearing on BBC Radio 4 last year (I think, time flies, too) about research that found that an albatross had a lower heartbeat flying over stormy seas than at rest on land.

    1. Although, that is to do with fighting tactics, and not aerodynamics.

      cr

      1. The Germans found out before WW2 and the British in the first couple of years that the Vic formation is a poor formation for air fighting at least for fighters.

        1. Yes, the link JezGrove posted goes into some detail about that.

          But I would guess that in a vic formation of aircraft, the followers were wide enough apart to keep out of any aerodynamic effects.

          cr

  10. Given the persistence of wing tip vortices in airliners – such that following planes have to stay miles back – it seems to me obvious that the following birds must be getting aerodynamic effects from the bird ahead. They cannot avoid it. And since they choose to fly in that formation, it must be advantageous (either that, or there is some other advantage – which is not apparent – that outweighs any disadvantages).

    The alternative formation, avoiding most aerodynamic effects, would be a very wide-angle vee, but they don’t use that.

    cr

    1. How good an analogue are rigid non-flapping aircraft wings for flapping, flexible-in-2-planes bird wings? Are their wake patterns even remotely similar?

      1. I agree there are probably big differences between the wake of a fixed wing and a flapping wing. However I don’t think a flapping wing would generate LESS disturbance in its wake than a fixed one, so my initial supposition – the the birds behind MUST be feeling the aerodynamic effect of the one in front – still holds, I think.

        In fact, having since viewed the video, this is the case, but it’s quite complex.

        cr

  11. But for some reason I find a flock of ibises following their human foster parent in a microlight to be ridiculously funny.

    A weirs sense of humour, I have.

    cr

  12. I wonder if sight lines also are a factor. Geese, for example, have eyes well to the side of the head and probably do not see well straight ahead. In that case, the V formation could be a natural result of optimizing visual contact with birds ahead.

      1. Since I don’t have an Archaeopteryx skull to hand (shameful, isn’t it?), I had to hunt a little. Published figures make it look as if the eyes look out completely laterally, but if you can find a figure showing the shape of the frontal bones, you’ll see there is something like a 20 to 30 degree angle between the orientations of the orbit edges. See, for example, fig 1 of this paper (Paläontologische Zeitschrift (2014) 88:211–221 , DOI 10.1007/s12542-013-0186-0). So, some overlap in the central field for feeding behaviors, but about a 330 degree field of view to keep an eye out for bigger and toothier diners.
        Short version – the eye placement seems to pre-date flight, except in some specialist predatory birds.

        1. Actually, I was kind of joking. Things like these tend to co-evolve because having one trait but not the other would result in a non-functioning organism. Of course, things are usually more complicated than this as the angle of the v may vary with the eye position, the behavior of predators may be involved, etc.

    2. Geese, like all (most?) birds have two maculae, one opposite the centre of the cornea and one completely at the back -relative to the head, that is. So they have excellent vision in front of their heads.

      1. A friend of mine (Jan Worst) once projected on the corneas of a raptor (a hawk iirc) from the front with a keratometer: 2 perfect half circles!

    3. The general explanation for eye placement is that the eaters have forward-facing eyes and the eaten have sideways-facing eyes so they approach a 360 degree field of view. So I see geese with eyes on the side of their head, and think “grazers”.

      1. Owls have indeed forward facing eyes, but even though they don’t have a double macula, they have a macular ‘streak’.

    4. Most of those formations seem to be quite narrow-angle vees, whereby the following birds must be in ‘dirty air’ from the one in front. I think, if the birds just wanted to keep ‘in touch’ without any aerodynamic effects, they could/would fly in a much wider vee.

      cr

      1. Your point is correct in that it could be either a wide or a narrow V (or even a broad front), if ‘keeping in view’ were the function. As said, these bird have a good visual acuity in front of them.
        The narrow V points to aerodynamics, as the video shows.

  14. Science article read, and video watched. Very interesting, with an obvious result from an evolutionary point of view. Sad that in the few comments on the YouTube site, there were four muslims and two christians each ignorantly touting their god as the one responsible. We know, however, that the watchmaker truly is blind.

  15. Yeah, I always figured it was some sort of drift or other trick of wind that helps all the birds in the flock.

    Of course, as we all know, birds didn’t start flying in this formation until 1992’s masterpiece The Mighty Ducks. It was only after that film that birds realized what a great idea The Flying V is.

  16. I believe that in flocks of geese, cranes and such like that fly in Vs the lead bird drops back after a while and another bird takes the lead. That would also be consistent with the energetic economy hypothesis.

  17. Finally managed to check this video (it’s that sort of day).

    It appears that in a V formation, the birds can see straight ahead better than if they were, e.g., in a line – but I suppose that isn’t very important because if they were, e.g., in a line, they’d still be moving around a mean position, getting a view ahead.

    … if the question is what they are in a flat V-formation for, I could ask what other shape would make any sense – a straight line (I’ll check the comments above for this obvious question)? Or a murmuration – perhaps only for small enough birds?

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