Breathing with the Earth
251
to use wristwatches as compasses. The bees also had a polarized light
system that could determine the sun's direction through light clouds or
forest canopy. Even more amazing, Frisch found, the scouts told workers
back at the hive where the flowers were by means of a dance using the
sun's angle and the direction to earth's center (the gravity vector) as
references. However, Frisch noted that bees could still navigate between
food and home just as well on completely overcast days, when the sun's
angle and polarized light weren't available. There had to be a backup
system.
It soon turned out that homing pigeons had the same abilities. In
1953 G. Kramer inferred that the birds must have a compass in addition
to a map of remembered landmarks from the way they immediately
pointed their beaks toward home after circling once after release. Soon
others found the same kind of sun compass as bees used, but the pigeons
could also steer perfectly on cloudy days. Back in 1947, H. L. Yeagley
had had the temerity to suggest in the Journal of Applied Physics that
pigeons might have a magnetic sense that allowed them to use the
earth's field just as we use magnetic compasses. He was ridiculed and
"refuted" by a few inadequate experiments—such as placing a pigeon in
a variety of electromagnetic fields and noting that it seemed to be com-
fortable! Others, including Yeagley, attached small magnets to the
birds' heads or wings, but found no clear-cut changes in their flight
patterns.
Only a few researchers quietly looked into the matter further. After
Hans Fromme of the Frankfurt Zoological Institute noted in the late
1950s that caged European robins faced longingly in their normal south-
west migratory direction even when they were kept from seeing sun and
stars, their usual signposts, his co-worker Friedrich Merkel discovered
that, insulated from the earth's field by a steel cage, they no longer faced
in one particular direction. Furthermore, by changing the orientation of
the surrounding field with coils, he could give the birds a false sense of
where southwest was. The experiment was validated with indigo bunt-
ings several years later.
There the matter rested until 1971, when William T. Keeton of Cor-
nell realized that the pigeon's magnetic sense, if it existed, would be
overshadowed by its sun compass, so naturally magnets affixed to the
birds would have no effect on clear days. He soon found that the same
birds released on a cloudy day got lost.
To study this magnetic
interference in
any weather, Keeton made
translucent contact lenses for his birds, then released them in the moun-
tains
of
northern
New
York.
Simulating dense clouds, the contacts