A new study published in the journal Nature has found evidence to suggest that birds adopt a V formation while in flight to improve aerodynamics and conserve energy. Royal Veterinary College researchers found that certain birds flap their wings with precision phasing, helping them to obtain maximum aerodynamic benefit as part of a flock.
V Formation Reduces Energy Expenditure
Previously, researchers conjectured that flocks of birds flew in a V configuration to burn less energy. In 2001, a different study investigated the V-shape formation adopted by pelicans; the authors determined that those pelicans situated at the front had higher heart rates, relative to those flying at the rear. On this basis, scientists made the logical deduction that the birds at the front expended more energy.
In order to remain air-bound, birds push air downwards and, subsequently, begin gliding. Regular wing movement generates a vortex within the air; this includes an updraft from the wings that provides lift (upwash), while air flowing from the bottom of the wing (downwash) pushes downward.
Steve Portugal, a comparative ecophysiologist based at the Royal Veterinary College in Hatfield, United Kingdom, who served as co-author on the latest study, recently spoke to the Smithsonian about the rudimentary principles of the afore-mentioned processes:
“The simple rule is upwash is good air, and downwash is bad air.”
On this basis, birds need to exploit the upwash of the vortex and researchers believe the V configuration method of flight enhances this. Creative Director at the Smithsonian Eric Schulze recently talked about this phenomenon, explaining that a particular bird will waste a lower amount of energy by flying slightly behind and above the bird at the head of the V formation. He compares this aerodynamic strategy to that of a cyclist in a bike race; cyclists tend to ride behind one another to save energy.
Ultimately, in doing so, Schulze indicates that geese can increase the maximum distance traveled by as much as 70 percent – during long, migratory flights – simply through using this strategy to conserve as much energy as possible.
When in this flight pattern, the birds are constantly changing position. The lead bird, eventually, drops to the back when tired and another assumes its place at the front of the V formation. In addition, this setup allows the birds to retain visual contact with each other, ensuring members of the flock are traveling in the correct direction.
New Study Investigates Flight Patterns of Northern Bald Ibis Bird
As studies into bird behavior in this migratory V formation are relatively sparse, Portugal and colleagues began studying the spectacle in an endangered species of bird – the northern bald ibis (Geronticus eremita), also known as the Waldrapp. To achieve this, the researchers teamed up with the conservation group Waldrappteam – an organization that aims to provide “financial and intellectual assistance for scientific based attempts of reintroducing…” the species to southern Europe.
The northern bald ibis typically occupies breeding grounds in barren, arid desert-like areas and rocky habitats. Nesting sites are often found among past castles, ruins and walls and even in urban regions, but the birds tend to favor settlement near the banks of rivers and along streams. The animals consume a relatively diverse diet of creatures, including insects, earthworms, snails, fish, lizards, snakes, rodents and small birds. In terms of vegetation, the northern bald ibis feeds on berries, duckweed and aquatic plant-life.
When the birds are raised in captivity, they treat human beings as their parental figures and become dependent upon their captors for almost everything. This makes their reintroduction into the wild remarkably difficult. However, Waldrappteam helps to teach the ibis birds to follow their natural migration route.
Portugal’s research team observed the birds raised in a zoo in Vienna, Austria, while they were under the tutelage of Waldrappteam. In order to “teach” the birds, the team used a parachute aircraft to show them the correct migration route, towards Italy, over the course of several weeks. Before this lesson was delivered, the 14 birds were fitted with small, light-weight data loggers, specially designed by the Structure and Motion Laboratory to collect GPS and acceleration data. This informed the researchers about the position of the birds and what they were doing.
When adopting the V formation, trailing birds would fly along the wingtip path of the bird in front to catch their upwash, thereby easing their flight to reduce energy output. However, when positioned directly behind another northern bald ibis, they do entirely the opposite; under these circumstances, the bird will flap “off beat” to the bird ahead – an action that helps to circumvent the detrimental influence of downwash.
Portugal briefly reflected on his team’s research findings, during a recent press release:
“Birds flying in V formation flap with wingtip path coherence, meaning that their wingtips take the same path to maximize upwash capture. In contrast, birds flying in line flap in spatial antiphase, with wingtip paths maximally separated, to avoid adverse downwash.”
Previously, this form of flight wasn’t considered possible, since it requires – according to the research team – “… complex flight dynamics and sensory feedback.” Precisely how the birds achieve this feat is yet to be definitively confirmed. However, it has been suggested that the ibises employ a combination of highly sensitive wingtip receptors (filoplumes), reflex reaction circuits in the brain and vision to coordinate their movements.
The research could even have implications for the aviation industry. Airlines are dedicating time and money to determine how birds use updraft to their advantage, in the hope that they can use this knowledge to their advantage. During World War II, it is believed that bomber pilots noticed a reduction in fuel expenditure when flying in V formation.
By James Fenner