o or three hours old to the anxious warning note of the
parents, and squat motionless on the ground, though other sounds, such
as the excited clucking of a foster-mother hen, leave them indifferent.
They do not know what they are doing when they squat; they are obeying
the living hand of the past which is within them. Their behaviour is
instinctive. But the present point is the discriminating quality of the
sense of hearing; and that is corroborated by the singing of birds.
It is emotional art, expressing feelings in the medium of sound. On the
part of the females, who are supposed to listen, it betokens a
cultivated ear.

[Illustration: THE BEAVER

The beaver will gnaw through trees a foot in diameter; to save itself
more trouble than is necessary, it will stop when it has gnawed the
trunk till there is only a narrow core left, having the wit to know that
the autumn gales will do the rest.]

[Illustration: _Photo: F. R. Hinkins & Son._

THE THRUSH AT ITS ANVIL

The song-thrush takes the snail's shell in its bill, and knocks it
against a stone until it breaks, making the palatable flesh available.

Many broken shells are often found around the anvil.]

As to the other senses, touch is not highly developed except about the
bill, where it reaches a climax in birds like the wood-cock, which probe
for unseen earthworms in the soft soil. Taste seems to be poorly
developed, for most birds bolt their food, but there is sometimes an
emphatic rejection of unpalatable things, like toads and caterpillars.
Of smell in birds little is known, but it has been proved to be present
in certain cases, e.g. in some nocturnal birds of prey. It seems certain
that it is by sight, not by smell, that the eagles gather to the
carcass; but perhaps there is more smell in birds than they are usually
credited with. One would like to experiment with the oil from the preen
gland of birds to see whether the scent of this does not help in the
recognition of kin by kin at night or amid the darkness of the forest.
There may be other senses in birds, such as a sense of temperature and a
sense of balance; but no success has attended the attempts made to
demonstrate a magnetic sense, which has been impatiently postulated by
students of bird migration in order to "explain" how the birds find
their way. The big fact is that in birds there are two widely open
gateways of knowledge, the sense of sight and the sense of hearing.

Instinctive Aptitudes