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Tuesday, February 3, 2015

why do birds fly in "V" ... science behind !

Watching bird [Birdwatching] a form of wildlife observation is an interesting activity.  It can be done with the naked eye, through a visual enhancement device like binoculars and telescopes, or by listening for bird sounds. Birds fly in search of food – return to their nests ~ and they move thousands of miles too. Bird migration is the regular seasonal movement, often north and south along a flyway, between breeding and wintering grounds.  Migration carries high costs in predation and mortality, including from hunting by humans.  The arctic tern holds the long-distance migration record for birds, travelling between Arctic breeding grounds and the Antarctic each year. Shorter migrations are common, including altitudinal migrations on mountains such as the Andes and Himalayas.   Migrating birds navigate using celestial cues from the sun and stars, the earth's magnetic field, and probably also mental maps.

As you could have seen often birds fly in V shape and it is believed that there is science behind this formation.  Scientists have observed  that birds position themselves and time their wing beats so perfectly that, according to aerodynamic theory, they minimize their energy use. It's a task that requires each bird to monitor subtle changes in its wing mates' flight and alter its own path and stroke accordingly. A ‘ V ’ formation (sometimes called a skein) is the symmetric V-shaped flight formation of flights of geese, ducks, and other migratory birds. V formations also improve the fuel efficiency of aircraft and are used on military flight missions.  The formation  makes flight easier, or they could simply be  following the leader. Squadrons of planes can save fuel by flying in a V formation, and many scientists suspect that migrating birds do the same.

Scientists from the Royal Veterinary College fitted data loggers to a flock of rare birds that were being trained to migrate by following a microlight. This revealed that the birds flew in the optimal position - gaining lift from the bird in front by remaining close to its wingtip. The study, published in the journal Nature, also showed that the birds timed their wing beats.

As a bird's wings move through the air, they are held at a slight angle, which deflects the air downward. This deflection means the air flows faster over the wing than underneath, causing air pressure to build up beneath the wings, while the pressure above the wings is reduced. It is this difference in pressure that produces lift. Flapping creates an additional forward and upward force known as thrust, which counteracts the weight and the "drag" of air resistance. The downstroke of the flap is also called the "power stroke", as it provides the majority of the thrust. During this, the wing is angled downwards even more steeply. This  latest study tracked and monitored the flight of every bird in the flock - recording its position, speed and heading as well as every wing flap. This was possible thanks to a unique conservation project by the Waldarappteam in Austria, which has raised flocks of northern bald ibises and trained them to migrate behind a microlight. The aim of this unusual project is to bring the northern bald ibis back to Europe; the birds were wiped out by hunting, so the team is retraining the birds to navigate a migration route that has now been lost.

Just as the birds save energy by gaining lift from other birds, many companies that are developing unmanned aerial vehicles, or UAVs, are looking to copy the energy-efficient V formation.

With regards – S. Sampathkumar
21st Jan 2015

News credit : bbc.com

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