ch is the
specific emotional manifestation during the period of sexual activity.
Eventually the intruding male succeeded by persistent effort in
appropriating part of the occupied ground.

Thus we can actually witness the efforts of the individual to isolate
itself from members of its own kind, and can observe the immediate
consequences that follow from success or from failure. And from these
consequences we can infer that, within a certain range but in accordance
with the relative abundance of the species that dwell in it, every
corner of the available breeding ground will be explored and every
situation that evokes the appropriate response will be occupied.
Moreover, since the annual dispersion is not merely a repetition in this
season of that which occurred in a previous one, a progressive increase
in the area occupied will follow. Yet, if the majority of species desert
their breeding ground so soon as reproduction is ended, how can this be?
An answer to the question will be found in the fact that a bird has an
innate capacity to return to the neighbourhood of its birthplace, or to
the place wherein it had previously reared offspring--which means that
the results of prior process persist as the basis and starting-point of
subsequent process.

Bearing then in mind that the seeming peace in bird life around us in
the spring is but the expression of transitory adjustments in the
distribution of individuals and of species; bearing in mind how
widespread is the search for isolation each recurring season, how
frequently the search leads to competition and competition to failure,
and how failure implies a renewal of the search; bearing in mind that
situations, which appear to be eminently suitable for breeding purposes,
are passed by year after year and remain unoccupied, just because, for
reasons which have yet to be ascertained, the environment fails to
supply some condition which is essential if the inherited nature of the
bird is to respond--can there be any doubt that the general result of
the functioning of the disposition will be expansion; or, since no limit
is placed upon it from within but only from without--that is, by
unfavourable circumstances in the external world, that the expansion
will not merely be in one direction but in every direction?

If now, when reproduction is ended, all the impulses relating to it die
away, and the gregarious instinct again predominates, what are the
consequences to which this