Flying in a V shape, the evolutionary strategy of birds

Why do birds apply the V-shaped flying strategy? Discover the secrets of this strategy that allows them to save energy and optimize their trip.

Migratory birds travel hundreds or thousands of kilometers each year from their wintering grounds to their summer breeding grounds. When traveling, they always seek to optimize their trip by going with the current, avoiding crossing large stretches of ocean or resting in places with abundant food sources.

That is why migratory birds are so common in the wetlands of Spain. The most likely route between Western Europe and North Africa is the Strait of Gibraltar, meaning that most birds pass through the Iberian Peninsula during their migration, stopping strategically in ecosystems where food is most abundant.

One way to optimize a migratory flight is to fly in a V shape.

Flying in a V shape guarantees optimal aerodynamics

When a bird flies alone, it looks for the prevailing winds and heat currents to fly the greatest distance with the least effort. But when birds move in groups, things become easier. Each member of the flock does not necessarily have to find the best path to achieve the goal. All the birds ahead know where to go, which is enough for the rest to follow.

But flying in a V shape also offers significant aerodynamic advantages for everyone behind. The wing of a flying bird, under the influence of lift, creates a whirlpool behind it, a kind of stripe in the air, similar to the stripe left by ships moving on water, which quickly dissipates. However, its presence, however fleeting, can be of great use to the bird that follows it.

If the bird is placed in the correct position, it can use the upward effect of the vortex as a form of additional momentum and propel itself forward, reducing the effort required to maintain flight. This translates into net energy savings during the trip, which is important for long migrations.

Behind the bird in front, two vortices form behind its wings, so these places will be aerodynamically optimal to place two more birds. And relying on their wings, they turn again behind them and will be overtaken by other birds and so on. The result is an economical and effortless V-shaped flight with one bird in front (the only one that makes effort without energy savings) followed by others. The first position is often changed throughout the formation to distribute forces evenly.

A very carefully calculated design

fly in V shape

To position themselves in an optimal location and take full advantage of the aerodynamic benefits of V-shaped flying, birds use visual and tactile cues.

As birds learn, they understand what position they should take in relation to birds in front and to the sides, and they approach these positions by accurately calculating distances.

But the positions of the vortices are not always the same. Air speed, wind intensity, temperature, and other atmospheric variables can move the vortex closer or further away. Therefore, after finding a suitable place, everyone pays attention to the air current caused by the previous bird and precisely adjusts their position, looking for the place with the strongest vortex.

Another characteristic of migratory birds is the synchronization of wingbeats. This synchronization is also intuitive. By flapping all of them at the same time, they accompany the movement of the vortices with their wings, reducing the force of the flapping and optimizing its effect. This way, they maintain formation even when changing positions.

The “V” formation is an evolutionary advantage

Not all birds, not even migratory, they fly in a V shape in their flights. This is a characteristic feature of several groups such as ducks, geese, pelicans, herons, storks, cranes or ibis. The groups are not necessarily evolutionarily related.

V-shaped flying is thought to have been an independently acquired strategy by many different species of birds.

Flying in a V shape offers enormous evolutionary advantages. It improves energy efficiency during flight and consumes less energy during migration, resulting in greater survival and more successful reproduction.

Regarding the importance of conserving energy when flying in a V shape, a study led by researcher Henri Weimerskirch of the French National Center for Scientific Research and carried out on pelicans found that animals that fly in a V shape have a heart rate of 11 15% less than those that fly alone and the frequency of flapping is also reduced.

Other advantages of flying in a V shape

  • The V formation can also help birds avoid predators.
  • It is more difficult for a predator to catch a single bird in a V formation than a bird flying alone.
  • The V formation can also help birds find food.
  • Birds in front can detect food more easily and share this information with those behind.

In short, birds fly in a V shape to save energy, improve communication, avoid predators, and find food.

References:

Lissaman, PBS et al. 1970. Formation Flight of Birds. Science, 168(3934), 1003-1005. DOI: 10.1126/science.168.3934.1003
Portugal, SJ et al. 2014. Upwash exploitation and downwash avoidance by flap phasing in ibis formation flight. Nature, 505(7483), 399-402. DOI: 10.1038/nature12939
Waldron, P. 2014. Why Birds Fly in a V Formation. Nature.
Weimerskirch, H. et al. 2001. Energy saving in flight formation. Nature, 413(6857), 697-698. DOI: 10.1038/35099670

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