HOW do homing pigeons find their way home? Biologists at Oxford
University feel confident they are now closer to solving this persistent puzzle.
The answer, at least over short distances, seems to be that they follow those in
the know.
Over long distances, homing pigeons find their way back to base mainly by
using inbuilt magnetic 鈥渃ompasses鈥� and clues from familiar smells. But how
pigeons initially get their bearings has never been clear. 鈥淔inding a route back
from the release point to the home loft has several components,鈥� says Teresa
Burt, one of the Oxford researchers. 鈥淵ou first have to work out where you
补谤别.鈥�
Using opaque and transparent pigeon carriers, Burt and her colleague Tim
Guilford showed that birds with most visual information about their release site
before they were set free homed fastest. They placed both groups of birds at a
familiar release site for 5 minutes. After releasing the pigeons, they found
that those from opaque boxes spent 20 or 30 seconds longer circling the site
before setting off than those from the clear boxes. 鈥淰isual recognition of the
release site clearly counted,鈥� says Burt. 鈥淚t is as if the birds released from
opaque containers are trying to make certain of where they are, while the birds
from clear boxes already know鈥�.
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The team also found that birds with less visual information can exploit those
with more. When they released the birds in pairs鈥攐ne from an opaque box,
and one from a clear box鈥攖hey found that after circling the area, both
birds would leave together. The less clued-up bird would fly after the one from
the clear box, which would slow down to let the more disoriented bird catch
up.
How one bird can sense that the other knows the way back is still puzzling.
鈥淲e鈥檇 love to know how they do this,鈥� says Guilford. 鈥淧erhaps it is a simple
rule like if you see another bird flying fast and strong, then follow it, but we
aren鈥檛 sure.鈥� Why the more knowledgeable bird waits for the other is also a
mystery. Guilford suspects that it is not an altruistic act鈥攖ravelling in
pairs might help to lessen the risk of predation by falcons, for instance.
Burt and Guilford鈥檚 observations may help to explain another characteristic
of pigeons鈥攖hat, as Guilford says, the birds 鈥渨ill do almost anything to
stay in a flock鈥�. Because pigeons flock in haphazard patterns, there is little
aerodynamic benefit. 鈥淭he main benefits are reduction in an individual鈥檚 chance
of predation and the possibility of social exploitation of other flock members鈥�
knowledge of homing orientations,鈥� says Guilford.
The researchers will publish their results in the journal Animal
Behaviour. Sue Healy, a psychologist at the University of Newcastle, says
the results show for the first time that pigeons rely heavily on visual clues.
鈥淭he virtues of flocking are rarely considered to incorporate information
transmission of this kind,鈥� she adds. 鈥淭o my knowledge, this is the first
demonstration of a navigational decision being affected in this way.鈥�