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| New research shows that birds precisely time when they flap their
wings and position themselves in aerodynamic optimal positions, to
maximize the capture of upwash, or 'good air', throughout the entire
flap cycle, while avoiding areas of downwash or 'bad air'. |
Researchers using custom-built GPS and accelerometer loggers, developed
with funding from the Engineering and Physical Sciences Research
Council, (EPSRC), and attached to free-flying birds on migration, have
gained ground-breaking insights into the mysteries of bird flight
formation.
The research, led by the Royal Veterinary College, University of
London, proves for the first time that birds precisely time when they
flap their wings and position themselves in aerodynamic optimal
positions, to maximise the capture of upwash, or 'good air', throughout
the entire flap cycle, while avoiding areas of downwash or 'bad air'.
It was previously not thought possible for birds to carry out such
aerodynamic feats because of the complex flight dynamics and sensory
feedback required. The study, is published in the journal Nature, on Thursday 16th January 2014.
Dr Steve Portugal, Lead Researcher at the Royal Veterinary College,
University of London, said: "The distinctive V-formation of bird flocks
has long intrigued researchers and continues to attract both scientific
and popular attention, however a definitive account of the aerodynamic
implications of these formations has remained elusive until now.
"The intricate mechanisms involved in V-formation flight indicate
remarkable awareness and ability of birds to respond to the wingpath of
nearby flock-mates. Birds in V-formation seem to have developed complex
phasing strategies to cope with the dynamic wakes produced by flapping
wings."
Professor David Delpy, Chief Executive of the EPSRC said: "This is a
fascinating piece of research, providing a scientific answer to a
question that I suspect most people have asked themselves -- why do
birds fly in formation? The results will prove useful in a variety of
fields for example aerodynamics and manufacturing.
"The research is an excellent example of an international
collaboration involving inputs not only from many physical and
engineering science disciplines, but also the life sciences."
The mechanisms that the birds use is achieved firstly through spatial
phasing of wing beats when flying in a spanwise ('V') position,
creating wing-tip path coherence between individuals which will maximise
upwash capture throughout the entire flap cycle.
Secondly, when flying in a streamwise ('behind') position, birds
exhibit spatial anti-phasing of their wing beats, creating no wing-tip
path coherence and avoiding regions of detrimental downwash. Such a
mechanism would be available specifically to flapping formation flight.
Scientists captured the data for the study as the birds flew
alongside a micro-light on their migration route from their summer
birthplace in Austria to their wintering grounds in Tuscany, Italy. The
study is the first to collect data from free-flying birds and was made
possible by the logging devices custom-built at the Structure and Motion
Laboratory at the Royal Veterinary College.
The light-weight, synchronised, GPS and inertial measurement devices,
recorded within up to 30 cm accuracy where a bird was within the flock,
its speed, and when and how hard it flapped its wings. The precision of
the measurements enabled the aerodynamic interactions of the birds to
be studied at a level and complexity for the first time.
Dr Portugal and his team worked with the Waldrappteam, a conservation
organisation based in Austria, who are re-introducing Northern Bald
Ibises into Europe, after being extinct there for 300 years.
The 14 juvenile birds used in the study were hand-reared at Vienna
Zoo by human foster parents from the Waldrappteam. The birds were
trained to follow a micro-light 'mother-ship' to teach them their
historic migration routes to wintering grounds in Italy. Normally they
would learn this from adult birds, and without this help, the birds
would not thrive.
The birds are currently in Tuscany and the team hopes they will
remember the way to what should be their breeding grounds in Salzburg
later this year, without the help of the micro-light this time!
