I was watching a flock of pigeons this morning. Their path is quite erratic and I wondered how they decided when to all turn nearly simultaneously.
Has this been investigated? Does the same bird decide to turn each time or does just any bird decide to turn and the rest follow?
I know that flocking is a good defense. Predators pick a target and go for that and concentrating on any particular bird in a flock is difficult.
See my Staff Report: How does a flock of birds wheel and swoop in unison?
Flocks generally do not have leaders (although some may). The movement of the flock is an emergent property of the behavior of individuals obeying rather simple rules.
That was very interesting and very well written. Kudos Colibri.
Agreed, a most excellent report! Let me also say that I just love the term “boids” (from the last paragraph) especially if you say it in your head with a New Joisey accent.
Boids!
Michael Score?
I was gonna say most sucessful hunters…
Thanks. I suppose I could have searched first. Everything makes sense as should be because the theories are backed up by experimental results.
I’m still dubious about the energy savings in the V formation of geese.
Racing cyclists do a similar thing - it does actually work.
The difference, (and like David Simmons, I have wondered about this in the past), is that cyclists (and even stock cars drafting each other) have a certain amount of non-aerodynamic bulk that they are forcing through the air directly ahead of them, whereas geese (or other birds) are already pretty aerodynamic. Unless air resistance is reduced simply by the presence of (wing tip?) turbulence, it is difficult to see how each goose in echelon is significantly aided by the presence of an fairly aerodynamic body passing through the air ahead and to one side of its passage.
I am not claiming that the V does not work, only that I have never seen an explanation that makes the claim intuitively obvious.
Why? There is no question that drafting works, and the higher the speed the more the benefit. Even if the energy savings were just a few percent, there would still be a reason to use that flight pattern (and I suspect the energy savings is greater than just a few percent).
Maybe the use of the V is a throwback to a time when ancestors of geese weren’t so aerodynamic?
Although I only touched on it peripherally in the Staff Report, the energy savings has been experimentally verified. Pelicans have been found to have a much lower heart rate when flying in formation than when flying alone. Some studies have estimated that geese may be able to fly as much as 70% farther due to energy savings from formation flying.
This article has a good discussion of the aerodynamic effects of formation flying in birds:
Right on target!
Locally there are two or three flocks/groups of Canada Geeses that fly over the house going west about a mile to a large pond.
In the evening they fly east to who know where.
We see the lead bird dropping back to a spot in line on one side or the other quite often.
And not only in birds. Here’s a link to a NASA study on the fuel savings possible when jets fly in close formation:
This photo shows the effect of the wingtip vortices of a business jet. It’s evident that another plane could benefit from the “up” part of the vortex by flying just behind and off the wingtip.
The only thing I know for sure is that the numbers 5 and 6 planes in a 6 plane tandem V formation always used more fuel during a mission. I have no doubt that in perfectly smooth air and for short periods planes in formation might benefit. However station keeping over a long period necessitates constant small corrections in course and speed. These are maneuvers and maneuvers take energy.
As to goose heart rates, I can’t explain it. Maybe geese are better formation flyers than people in turbulent air.
That’s a large part of it. Birds are able to make much finer adjustments than aircraft, and can afford to fly closer to one another in any case since the consequences of touching another bird are far less severe than if aircraft come into contact.
As the article I linked indicates, it’s not actually drafting as in the case of a cyclist, but rather that the birds take advantage of updrafts produced by the wingtip vortexes of the other birds.
Quite possibly. However the Arctic Tern almost never lands on a 22000 mile (great circle distance) migration and does it without flying in formation. The accompanying photo also shows quite a separation between birds, behind and to the side. How many body lengths away from the bird does this beneficial effect occur? We have several thousand snow geese that winter here. I notice in their V formations they don’t necessarily keep a rigid separation from the goose ahead so as to always stay in the upwash part of the wing tip vortex. They wander around quite a bit.
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.
I’m willing to be convinced but so far I’m not.
Presumably the vortices off an F18 or a goose are less pronounced than those of this cropduster like plane, but there’s power back there for the taking.
Terns have high aspect ratio wings and relatively low wing loading - two factors that would make V-formation flight less beneficial.
The birds that tend to do this tend to be heavy: geese, swans, wood storks, etc. They have high wingloading and thus significant wingtip vortices. If you’re a goose flying with a bunch of other geese, it’s a natural and normal thing to put yourself in air that has an upward component.
