http://www.smh.com.au/articles/2004/02/05/1075853991021.html
Stone the crows, pigeons follow roads
February 6, 2004
Researchers have cracked the puzzle of how pigeons find their way home:
they just follow the main roads.
Zoologists now believe the phrase "as the crow flies" no longer means
the shortest most direct route between two points. They say it is
likely that crows and other diurnal birds also choose AA-suggested
routes, even though it makes their journeys longer.
Some pigeons stick so rigidly to the roads that they even fly round
roundabouts before choosing the exit to lead them back to their lofts.
Animal behaviouralists at Oxford University are stunned by their
findings, which follow 10 years of research into homing pigeons. For
the last 18 months, they have used the latest global-positioning
technology, allowing them to track the ground the birds covered to
within one to four metres.
"It really has knocked our research team sideways to find that after a
decade-long international study, pigeons appear to ignore their
in-built directional instincts and follow the road system," said
Professor Tim Guilford, Reader in Animal Behaviour at Oxford
University's Department of Zoology.
"For long distance navigation and for birds doing a journey for the
first time, they will use their in-built compasses and take sun and
star bearings.
"But once homing pigeons have flown a journey more than once, they home
in on a habitual route home, much as we do when we are driving or
walking home from work.
"In short, it looks like it is mentally easier for a bird to fly down a
road and then turn right. They are just making their journey as simple
as possible."
His team carried out dozens of tests with pigeons in Oxfordshire,
releasing them between 10 and 20 miles from their lofts, each with a
tiny GPS tracking device attached to their backs. Matching their
routes, they found most flew straight down the A34 Oxford bypass.
"It was almost comical watching one group of birds that we released
near a major A road. They followed the road to the first junction where
they all turned right, and a couple of junctions on, they all turned
left".
Not all of the pigeons did it all of the time, but there were enough
occasions when they did for the researchers to build up a pattern.
"We even had one bird flying down the road, going round the roundabout,
taking one of the turnings down that to another roundabout then leaving
the road.
"Up until now, we have always thought about the way that birds go in
terms of the energetics of the flight efficiency, which is the most
direct route home ... as in the phrase 'as the crow flies'. But the
answer is, they don't go as the crow flies, and neither, it is my
hunch, do crows. As they get familiar with the environment, they just
follow the obvious features which often don't take them directly home.
"That may sound trivial to some people, but to us that is quite
important because it is starting to get at the structure of a birds'
memories, and what the map looks like to a bird.
"We are genuinely surprised. It makes you think what did pigeons and
other birds did before we cluttered the landscape with all these linear
features. And it makes you think hard about how flexible animals are
amid what we have done to their landscape.
"Lots of animals have invaded and made use of the changes we have
provided for them. You only have to look at Trafalgar Square and how it
has become a fantastic three-dimensional cliff environment for pigeons
to live in.
"It's evolution in action.
"Maybe they were using rivers and coastlines before. But, when we got
our first tracks of birds flying up the dual carriageway and then
turning off the road to the village where their home loft was, we
thought, 'This shouldn't happen, but it's very exciting.'
"Roads and important things like roundabouts do appear to be very
attractive to birds. If they have made the journey before, the pigeons
are more likely to say, 'Well, I know this is south - the way I want to
be going - but rather than fiddle around with my in-built compass I'm
going to follow the A34, which will take me home nicely.' "
Peter Brian, general manager of the Royal Pigeon Racing Association,
based in Cheltenham, said: "Every Saturday you can see whole flocks of
pigeons flying up the M5. Professor Guilford's research in animal
behaviour and migration is renowned and there is a lot of credence to
what he is saying. I think his findings are spot-on."
The Daily Telegraph, London
The research in question appears to be the product of a D Phil
student’s work - http://users.ox.ac.uk/~abrg/navigation.html
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