I heard honking the other day. Not from cars, but geese migrating somewhere warmer. I saw two separate flocks merge and eventually reform into a bigger V. Are they trying to spell "Vancouver" or is something else going on with their V formations?
The common explanation seems to be that the arrangement enhances lift and reduces drag so flying together burns less energy than going alone. This would a good thing since Canada geese can fly for sixteen hours without stopping. And people like to use it to illustrate the benefits of teamwork.
As a bird flaps, the air at the tip of the wing spins off resulting in an upwash and a downwash. A second bird in the right position benefits from the upwash by an increase in lift without having to flap as hard.
For the most benefit, they're supposed to be about one-fourth of a wingspan from the bird in front. Some say that they don't actually space themselves out the way they should. So the benefits may be exaggerated. Rather than the often quoted 71%, the birds may only enjoy a 1 to 2% increase in range for a given amount of energy.
The lead bird and the last birds are better off than flying alone, but work harder than the rest and change positions once in a while. All that honking might have something to do with this. Speaking of which, the V arrangement might help with communications and being able to maintain visual contact. Apparently, it's still up in the air.