The V formation or the angular flight , also known as a wedge formation , is a V-shaped flight formation of flying geese birds , copods , wading birds or other larger migratory birds , which is used in particular to save energy. Often the V-formation is not symmetrical and one leg is shorter than the other.
V-formations are also used in military flight missions, see formation flight .
Flying in a V-formation helps the birds in a flock to cover long distances in an energy-efficient manner. Except for the first bird, all fly in the lift of the wake vortex (tip vortex) of the bird flying ahead. A small amount of lift helps the bird hold its own weight in flight (in the same way that a glider can gain or maintain altitude in thermal lift ). In a V-formation, each bird can achieve a reduction in air resistance , which increases the range. With the precise determination of the position of 393 short-billed geese in 54 formation flights, an average energy saving of 14% was calculated. Almost all of them benefited in their energy balance from flying in formation. The theoretically optimal position was taken by only nine of the animals examined, which allowed them to reduce the effort by 51%. Canada geese achieve an average of 10% energy savings from their formation flight with a theoretical energy saving potential of 35%. In the case of the Great White Pelicans , the actual energy savings could be measured using the heart rate.
The birds take turns at the top regularly. In this way, the stress is evenly distributed among many to all members of the swarm, and one after the other all enjoy the slipstream of other members of the formation.
Communication and collision control
Over 97% of short-billed geese do not keep the optimal energy-efficient distance. This indicates that the energy saving is not the only advantage of the formation flight.
The V-formation facilitates communication with each other and allows the birds to maintain visual contact with each other and to know the position of their neighbors. A good position determination of the neighboring birds serves to avoid collisions. Better communication with one another can play a role in orientation.
If birds fly in swarms in a V-formation, it is more difficult to avoid them. For the leader and perhaps some of the birds flying behind him, it is possible to avoid a flying object ( airplane or helicopter ), while for those who follow the risk of a bird strike , which leads to a collision with the flying object with sometimes devastating consequences. Birds in a V formation are also many times more endangered than individuals by illegal shooting - sometimes by launch systems; because the bullets in a shot load have a high probability of hitting more than one bird.
Susceptibility to wind
A wind-related impairment of the formation was suspected. It could be shown, however, that the flight positions are maintained with about the same precision in strong winds as on calm days, the mean depth was even more precise with increased wind.
The optimal speed of long-haul flights results primarily from energy optimization (energy / distance) and depends on the wind and altitude, but also on the rate of ascent and the swarm size. In addition, intermediate destinations such as preferred resting and feeding areas can occasionally trigger a less energy-efficient and higher flight speed.
Chaotic flight formation
Many smaller migratory birds such as starlings or dunlins move in three-dimensional formations that appear chaotic. But even in these flocks, the animals keep their distances and angles to some of their neighbors relatively constant.
- Dietrich Hummel: The performance savings in association flight. In: Journal of Ornithology. Volume 114, No. 3, 1973, pp. 259-282.
- PBS Lissman, CA Shollenberger: Formation flight by birds. In: Science Volume 168, 1970, pp. 1003-1005.
- JP Badgerow, FR Hainsworth: Energy savings through formation flights? A reexamination of the vee formation. In: J. theor. Biol. Volume 93, 1981, pp. 41-52.
- C. Cutts, J. Speakman: Energy savings in formation flight of pink-footed geese. In: J. theor. Biol. Volume 189, No. 1, 1994, pp. 251-261.
- Henri Weimerskirch, Julien Martin, Yannick Clerquin, Peggy Alexandre, Sarka Jiraskova: Energy saving in flight formation. In: Nature Volume 413, No. 6857, 2001, pp. 697-698. doi : 10.1038 / 35099670 .
- William Blake, Dieter Multhopp: Design, performance and modeling considerations for close formation flight. In: CLJ Volume 150, 1998, p. 2.
- F. R. Hainsworth: Precision and dynamics of positioning by Canada geese in formation. In: J. exp. Biol. Vol. 128, 1987, pp. 445-462.
- As an example: Airplane crash in the Hudson River, 2009.
- Anders Hedenstrom, Thomas Alerstam: Optimal flight speed of birds. In: Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences. Volume 348, No. 1326, 1995, pp. 471-487. doi : 10.1098 / rstb.1995.0082 .
- Peter F. Major, Lawrence M. Dill: The three-dimensional structure of airborne bird flocks. In: Behavioral Ecology and Sociobiology Vol. 4, No. 2, 1978, pp. 111-122.