t under
all circumstances, namely, loudness and specific distinctness; and if,
in addition to serving the purpose of disclosing the positions of the
males, they serve to evoke some emotion in the female, which helps to
further the biological end of mating, so much the more reason is there
for their survival.

There can be no question that this ingenious and attractive theory, if
it were true in its special application to song, would immensely
simplify interpretation, and moreover that preferential mating would
contribute not a little to the success of the whole territorial system.
No one can deny the strength of the argument: that the sexual instinct,
like all other instincts, must require a stimulus of an appropriate
kind; that the effect of the sexual call upon the female cannot be
neutral; and hence the probability that stimulation varies too; no one,
I say, can question the strength of this evidence, and, one might add,
of the evidence derived from the analogy of the human voice. But when we
have said this, we have said all; and our acceptance of the hypothesis,
so far as song is concerned, must remain provisional so long as the
evidence remains but secondary evidence.

CHAPTER V

THE RELATION OF THE TERRITORY TO THE SYSTEM OF REPRODUCTION

In the first two chapters I tried to show that the inherited nature of
the male leads it to remain in a definite place at a definite season and
to become intolerant of the approach of members of its own sex, and that
a result is thus attained which the word "territory" in some measure
describes. But the use of this word is nevertheless open to criticism,
for it denotes a human end upon which the highest faculties have been
brought to bear, and consequently we have to be on our guard lest our
conception of the "territory" should tend to soar upwards into regions
which require a level of mental development not attained by the bird. It
is necessary to bear this in mind now we have come to consider the
meaning of the territory, or rather the position that it occupies in the
whole scheme of reproduction.

Relationship to a territory within the interrelated whole of a bird's
life serves more than one purpose, and not always the same purpose in
the case of every species. We have only to glance at the life-histories
of divergent forms to see that the territory has been gradually adjusted
to suit their respective needs--limited in size here, expanded there, to
meet new condi