# Who leads a flock of birds? **URL:** \ **Category:** Factual Questions\ **Created:** [November 28, 2006, 9:28pm UTC](https://boards.straightdope.com/t/who-leads-a-flock-of-birds/382129 "2006-11-28T21:28:20Z")\ **Posts on this page:** 15\ **Page:** 2
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [November 29, 2006, 4:39am UTC](https://boards.straightdope.com/t/who-leads-a-flock-of-birds/382129/21 "2006-11-29T04:39:21Z")
[QUOTE=Squink] Presumably the vortices off an F18 … are less pronounced than [those of this cropduster like plane](http://en.wikipedia.org/wiki/Image:Airplane_vortex.jpg) [/QUOTE] No, the F-18 would exhibit much stronger vortices at low speed. (Someone shoulda posted that F-18 link sooner!) ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [November 29, 2006, 4:46am UTC](https://boards.straightdope.com/t/who-leads-a-flock-of-birds/382129/22 "2006-11-29T04:46:50Z")
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. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [November 29, 2006, 4:57am UTC](https://boards.straightdope.com/t/who-leads-a-flock-of-birds/382129/23 "2006-11-29T04:57:37Z")
[QUOTE=David Simmons] Quite possibly. However the [Arctic Tern](http://library.thinkquest.org/3500/arctic_tern.html) almost never lands on a 22000 mile (great circle distance) migration and does it without flying in formation. [/quote] 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. > [@](#): > > Right but in formation flying you are not drafting. Drafting depends upon getting into the low pressure area behind the car in front. Because of their shape, aircraft have an exceedingly small low pressure area behind, and in formation you aren’t behind anyway. 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. > [@](#): > > I’m willing to be convinced but so far I’m not. 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: [Kin selection and reciprocity in flight formation?](http://beheco.oxfordjournals.org/cgi/content/full/15/1/158) > [@](#): > > Energy saving is well supported both theoretically (see Badgerow and Hainsworth, 1981; Hummel, 1995; Lissaman and Shollenberger, 1970) and empirically (see Badgerow, 1988; Cutts and Speakman, 1994; Hainsworth, 1987, 1988; Hummel, 1995; Speakman and Banks, 1998). Weimerskirch et al. (2001) showed that great white pelicans (Pelecanus onocrotalus) have lower heart and wing beat rate, glide more often, and save as much as 11–14% energy when flying in the vortex wake from another bird ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [November 29, 2006, 5:08am UTC](https://boards.straightdope.com/t/who-leads-a-flock-of-birds/382129/24 "2006-11-29T05:08:03Z")
[QUOTE=David Simmons] 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. [/QUOTE] 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. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [November 29, 2006, 2:02pm UTC](https://boards.straightdope.com/t/who-leads-a-flock-of-birds/382129/25 "2006-11-29T14:02:52Z")
[QUOTE=Colibri] 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. [/quote] 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. > [@](#): > > great white pelicans (Pelecanus onocrotalus) have lower heart and wing beat rate, glide more often, and save as much as 11–14% energy when flying in the vortex wake from another bird 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. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [November 29, 2006, 2:28pm UTC](https://boards.straightdope.com/t/who-leads-a-flock-of-birds/382129/26 "2006-11-29T14:28:48Z")
[QUOTE=David Simmons] 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. [/QUOTE] 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. > [@](#): > > 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. 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. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [November 29, 2006, 2:36pm UTC](https://boards.straightdope.com/t/who-leads-a-flock-of-birds/382129/27 "2006-11-29T14:36:27Z")
[QUOTE=Colibri] This article has a good discussion of the aerodynamic effects of formation flying in birds: [V-formation flying in birds](http://www.aerospaceweb.org/question/nature/q0237.shtml) [/QUOTE] That’s a good article, but I’m curious/confused about this bit: > [@](#): > > The majority of the benefit goes to the birds further aft, but the front bird does still gain some reduction in drag. The presence of the two birds flanking the leader helps to dissipate the downwash off the lead bird’s wingtips and reduces the induced drag this bird experiences. These two flanking birds also benefit from a similar reduction in drag if outboard birds flank them as well. In other words, the birds in the middle of each of the lines forming the V are in the best position. These birds benefit from the upwash off the lead birds as well as off the trailing birds. This additional bonus means that birds in the middle experience less drag than either the lead bird or the bird at the end of each line. 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? ---
**Author:** ![twickster](https://avatars.discourse-cdn.com/v4/letter/t/ec9cab/32.png) [@twickster](https://boards.straightdope.com/u/twickster)\ **Post date:** [November 29, 2006, 2:37pm UTC](https://boards.straightdope.com/t/who-leads-a-flock-of-birds/382129/28 "2006-11-29T14:37:51Z")
[QUOTE=tomndebb] …I am not claiming that the V does not work, only that I have never seen an explanation that makes the claim intuitively obvious. [/QUOTE] If it’s intuitively obvious, it doesn’t need an explanation. [/semantic nitpick] ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [November 29, 2006, 4:56pm UTC](https://boards.straightdope.com/t/who-leads-a-flock-of-birds/382129/29 "2006-11-29T16:56:10Z")
Just a quick note on the[F/A-18 tests referenced earlier.](http://www.dfrc.nasa.gov/Newsroom/X-Press/stories/103101/new_aff.txt.html) 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 current flight phase is mapping the wingtip vortex effects of the lead aircraft on the trailing aircraft. Wingtip vortex is a spiraling wind flowing from the wing during flight. The vortex causes rolling, yawing and pitching moments on the trailing aircraft that must be counteracted with changes in the aircraft’s control surfaces. > > It is a difficult task for the trailing pilot to maintain the proper position while flying in the vortex. 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. > [@](#): > > Modeling the vortex is a significant part of AFF research. The most desirable scenario is for an aircraft’s autopilot to control the formation. Data from these flights are being used to develop an aerodynamic model of an F/A-18 flying in the vortex field of another F/A-18. These data will be used to design and test the autonomous autopilot. 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. 😉 ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [November 29, 2006, 5:47pm UTC](https://boards.straightdope.com/t/who-leads-a-flock-of-birds/382129/30 "2006-11-29T17:47:41Z")
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. > [@](#): > > Maybe flying alone creates anxiety in the penguin because of increased vulnerability to predators while flying with others calms them. 😉 I have no doubt that penguins would experience considerable anxiety in flight, whether alone or in flocks. 😃 ---
**Author:** ![GusNSpot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gusnspot/32/436_2.png) [@GusNSpot](https://boards.straightdope.com/u/GusNSpot)\ **Post date:** [November 29, 2006, 5:56pm UTC](https://boards.straightdope.com/t/who-leads-a-flock-of-birds/382129/31 "2006-11-29T17:56:27Z")
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. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [November 29, 2006, 5:56pm UTC](https://boards.straightdope.com/t/who-leads-a-flock-of-birds/382129/32 "2006-11-29T17:56:36Z")
[QUOTE=David Simmons] 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. [/QUOTE] [Here](http://www1.dfrc.nasa.gov/Gallery/photo/AFF/Small/EC01-0328-4.jpg)’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. > [@](#): > > birds don’t have autopilots but themselves must compensate for the vagaries of the airflow for long perriods. 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. ---
**Author:** ![marshmallow](https://avatars.discourse-cdn.com/v4/letter/m/df705f/32.png) [@marshmallow](https://boards.straightdope.com/u/marshmallow)\ **Post date:** [November 29, 2006, 6:18pm UTC](https://boards.straightdope.com/t/who-leads-a-flock-of-birds/382129/33 "2006-11-29T18:18:36Z")
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… ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [November 29, 2006, 6:31pm UTC](https://boards.straightdope.com/t/who-leads-a-flock-of-birds/382129/34 "2006-11-29T18:31:57Z")
[QUOTE=mstay] It seems to me that a large flock could face the possibility of splitting in half… [/QUOTE] That happens; see this video of [flocks of starlings interacting](http://www.youtube.com/watch?v=yjYDefB6OYE). ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [November 29, 2006, 6:35pm UTC](https://boards.straightdope.com/t/who-leads-a-flock-of-birds/382129/35 "2006-11-29T18:35:10Z")
[QUOTE=mstay] 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… [/QUOTE] 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. [Previous page](https://boards.straightdope.com/t/who-leads-a-flock-of-birds/382129.md?page=1)