s removal
from a certain position. And inasmuch as this result will be obtained
whether the retreat is brought about by fear of an opponent or by
physical exhaustion, it is manifest that too much significance need not
be attached to the amount of injury inflicted. It is necessary to bear
this in mind, because it is held by some, who have carefully observed
the actions of various species, that overmuch importance is attached to
the conflicts, that in a large number of instances they are mere
"bickerings" and lead to nothing, and that they are now only "formal,"
which means, I suppose, that they are vestigial--fragments of warfare
that determined the survival of the species in bygone ages. But if the
conclusion at which we have just arrived be correct, if we can recognise
a single aim passing through the whole of the warfare--and that one the
removal of an intruder from a certain position, then we need no longer
concern ourselves as to the degree of severity of the battles--we see it
all in true perspective. Neither exhaustion nor physical inability are
the sole factors which determine the nature and extent of the fighting;
there is a more important factor still--position. According, that is to
say, to the position which a bird occupies whilst fighting is in
progress, so its pugnacious nature gains or loses susceptibility, and it
is this gain or loss of susceptibility which I refer to when I speak of
the fighting as being controlled.

What we have then to consider is the relation of "susceptibility" to
"position." We can explain the relationship in two ways. We can say that
the part of the nature of the male which leads to the occupation of a
territory, and is partly hereditary and partly acquired, is stronger
than the part which leads the bird to fight, and which is conditioned by
the presence of a female, and that consequently when the male passes the
boundary, the impulse to return asserts itself and the conflict ceases;
or we can say that the occupation of a territory is the condition under
which the pugnacious instinct is rendered susceptible to stimulation,
that the stimulus is supplied by the intruder, and that when the male
passes outside the accustomed area its instinct is no longer so
susceptible and it therefore retires from the conflict.

[Illustration: Long-tailed Tit Males fighting for possession of
territory. The feathers have been torn from the crown of the defeated
and dying rival.

Emery Walker ph.sc.