[Illustration]
Man is the tool user pre-eminent in the animal world, but he does not
stand completely alone in this. Here and there, in quite different
groups of animals such as insects, mammals, and birds, a few kinds have
forged a little ahead of the rest of their near relatives and show the
very beginning of tool using.
The song thrush of Europe is perhaps a borderline case. It feeds in
part on snails. To get the soft edible animal out of its shell, it
carries or drags the snail to a favorite rock, its anvil, and there
hits it against the anvil until the shell is broken and its contents
exposed. The question is, can this be considered as using a tool? If
the song thrush moved or prepared the rock, which it does not do,
there would be no question that it was a tool. The sea otter brings
a stone from the bottom of the ocean and places it on its floating
body to use as a similar anvil in cracking hard objects, and this
undoubtedly is the use of a tool. At the other extreme are many species
of birds that beat their prey on branch or ground, wherever they happen
to be. The song thrush is certainly an advance over that, and can, I
think, be considered as using a tool in a primitive way.
A few other species, too, bring shellfish to special places. Gulls on
our coasts pick up mussels and clams and, flying over a rock or some
other hard surface, drop the shellfish, and follow it down. If the
shell is broken, the dish is ready for the gull; if the shell is not
broken the gull takes the shellfish up to a higher altitude and tries
again. In places where hard-surfaced roads are conveniently located
gulls have learned to use them as shell-breaking places, and such roads
become littered with shells.
Crows of more than one species also use the same routine in breaking
open shellfish, and they, too, have learned to use special hard
surfaces, such as masonry walls, on which to drop the shellfish.
PAINTING A BOWER The satin bowerbird of Australia, a species known to
science as _Ptilonorhynchus violaceus_, has also been considered as a
case in point when discussing the use of tools. The birds are somewhat
larger than a robin, the male glossy blue-black, the female greenish.
The male of this species constructs an elaborate bower, presumably for
courtship purposes. It makes it of sticks and twigs, and decorates it
with bright and curious objects such as shells, feathers, bits of
bone, and fruits, as do several other species of bowerbirds. But the
satin bowerbird is unique in painting the inside of its bower. Fruit
is crushed in its bill, and the bird, using its bill as the tool or
paintbrush, smears the fruit juice on the sticks on the inside of the
bower. While this is a wonderfully strange habit, and apparently unique
in the bird world, it is doubtful if this behavior can be considered as
using a tool. If the satin bowerbird used a twig, or a wad of moss or
fiber, which it does not do, in spreading the paint, the case would be
clear.
The clearest case is that of the woodpecker finch of the Galápagos
Islands. _Camarhynchus pallidus_ is its proper name. It is one of a
group of dull-colored finches restricted to the Galápagos Islands.
Before it became known that one species used a tool, the chief claim to
fame of the group was that it, along with some other Galápagos Island
animals, such as the giant tortoises, had a great influence on Darwin's
thinking which resulted in his working out the theory of evolution as
set forth in his _Origin of Species_.
The woodpecker finch feeds largely on insects it gets by searching
and probing on the ground, and on the trunk and leaves of trees. In
searching crevices the woodpecker finch is handicapped by its rather
short, thick bill, and to offset this, it picks up a slender, short
length of stick, or the spine of a prickly pear, and with this in its
bill, pokes into crannies. The insects, disturbed or driven out, are
seized. Sometimes the woodpecker finch digs into the tree trunk and
then gets a stick to probe with; sometimes it carries its probe about
with it, poking in crannies until prey is disturbed. Then the stick is
dropped and the food seized.
We have seen how several birds are perhaps borderline cases in
using tools. They use certain special aspects of their environment
in preparing their food, and use it time after time. It's probably
instinctive behavior, but learning is shown in the gulls and crows
coming to recognize and use a hard-surfaced road in breaking open their
shellfish. The use of a probe by the woodpecker finch is a clear and
unique case of tool using by a bird.