ut is pugnacious when it has secured a
territory, shows it; the behaviour of the resident, which temporarily
joins the flock and is there sociable, shows it; and it is shown also by
the determination with which both opponents fight when the question of
ownership of a station is in dispute. And of all the facts we have
reviewed, this is perhaps the most important in relation to our present
subject, for it demonstrates that the change from sociability to
hostility is not merely an incident of the sexual season, not merely an
indirect result of the functioning of the general disposition which
leads to the establishment of a territory, but that it is intimately
associated with the whole process, and that the particular part of the
bird's nature which is concerned is so nicely balanced that it will
respond under one condition and one only.

Thus we are led to the only conclusion which seems consistent with the
facts, namely that there is a relationship between the "territory" and
the hostility.

If we are satisfied that all this warfare is not merely an expression of
an instinct which is serviceable in another direction, what part does it
play in the whole scheme of reproduction?

The young of many birds are delicate at birth and unable to withstand
exposure to cold, and in the previous chapter we came to the conclusion
that the territory was serviceable in that it provided an adequate
supply of food in the vicinity of the nest, and thus obviated the
necessity of the parents being absent from them for long. But manifestly
no matter how active a male may be in driving away members of its own
sex and kind, it will neither make its position secure, nor insure a
supply of food for its young, so long as any number of individuals of
different kinds are allowed to establish themselves in the same space of
ground. On the one hand, then, we have the fact that there is constant
strife between males of close affinity, whilst on the other, we know
that many species require like conditions of existence and are bound to
assemble wherever these conditions are suitable; and we can infer that
the territory would fail to serve its purpose if no restriction were
imposed upon the measure of such assemblies.

The question then arises: Does all this warfare contribute towards the
attainment of reproduction? Not far from my house there is a small water
meadow, three acres in extent, which for some years has been derelict
and is now overgrown