[Illustration]
If birds can count, it's a rather rudimentary thing--perhaps no more
than impressions of the size of groups. The widely known example
showing that birds don't seem to distinguish between one and two
persons is the ruse used by bird photographers and students of birds
who are using blinds from which to watch the birds at close range.
The hide, or blind, is a little hut built perhaps a few feet from the
nest to be photographed. If the photographer enters the blind in the
sight of the parent birds, and conceals himself there, the birds who
saw him go in will be a long time in coming to the nest and in resuming
their normal activities. But if the photographer takes a companion
with him, both go into the blind and conceal themselves, and then
one of them goes away leaving the other concealed, the bird quickly
disregards the intrusion and goes about its activities as though no one
were left in the blind. This subterfuge has long been used and is very
successful. Apparently the bird is unable to distinguish between the
two people that arrive at the nest and the one only that leaves, and
behaves as if both had gone away.
In my duck-hunting days a duck hunter who used wooden decoys told me
he was sure that there was a certain number of decoys necessary before
they were effective.
The decoys were wooden blocks, carved and painted to resemble
life-sized ducks, weighted to float like them, and anchored in shallow
water in a flock within gunshot range of the blind in which the duck
shooter sat. The idea was that ducks flying by would see the flock on
the water, assume that here was a safe resting place, and fly in and
light, or attempt to light among them, giving the wild-fowl gunner an
opportunity to shoot the wild birds.
The duck shooter claimed that if less than twenty-five or thirty decoys
were put out in the flock, the setup was much less effective than if
more than twenty-five to thirty decoys were used. He thought that the
ducks could distinguish between less than twenty-five or thirty and
more than twenty-five to thirty, and favored the latter. Though this is
distinguishing between greater and lesser amounts, it hardly comes in
the category of counting.
DISTINGUISH "MORE" FROM "LESS" However, a series of experiments
summarized on Page 121 in the periodical _Bird Banding_ for 1940 seem
to indicate that birds can distinguish between different numbers of
things, such as peas and numbers of dots. The birds, including pigeons,
parakeets, and jackdaws, were trained either to choose a certain
number of objects under certain circumstances, or to choose between
two quantities of objects with reward and punishment motivation. It
was found that these birds were able to distinguish up to a maximum
of six. That this is really counting in the human sense of the term,
which is linked with speech or written symbols, is improbable, but it
does indicate, as one would expect, that birds do at times distinguish
between different quantities, and sometimes with considerable
precision.