A very instructive case is the behaviour of the song-thrush when it
takes a wood-snail in its beak and hammers it against a stone, its
so-called anvil. To a young thrush, which she had brought up by hand,
Miss Frances Pitt offered some wood-snails, but it took no interest in
them until one put out its head and began to move about. The bird then
pecked at the snail's horns, but was evidently puzzled when the creature
retreated within the shelter of the shell. This happened over and over
again, the thrush's inquisitive interest increasing day by day. It
pecked at the shell and even picked it up by the lip, but no real
progress was made till the sixth day, when the thrush seized the snail
and beat it on the ground as it would a big worm. On the same day it
picked up a shell and knocked it repeatedly against a stone, trying
first one snail and then another. After fifteen minutes' hard work, the
thrush managed to break one, and after that it was all easy. A certain
predisposition to beat things on the ground was doubtless present, but
the experiment showed that the use of an anvil could be arrived at by an
untutored bird. After prolonged trying it found out how to deal with a
difficult situation. It may be said that in more natural conditions this
might be picked up by imitation, but while this is quite possible, it is
useful to notice that experiments with animals lead us to doubt whether
imitation counts for nearly so much as used to be believed.
§ 6