t without some reason, are responsible for its
initiation. Granting, then, that there is this congenital disposition,
what relation does it bear to the song? Without a doubt the song is
likewise founded upon a congenital basis; it is truly instinctive, and
as such requires appropriate stimulation; furthermore the male sings
only when in occupation of its territory. Having regard to these two
facts we might say that the territory is the stimulus to the song. But
this can scarcely be a true interpretation, for inasmuch as the stimulus
would be relatively constant, a relatively constant response ought to
follow, and even a slight acquaintance with the daily round of
behaviour will furnish plenty of evidence to the contrary, seeing that
the song, though persistent, is never continuous--in fact there are long
periods of silence during the daytime, and only in the morning and the
evening does the male become really vociferous. What then is the
stimulus? Through awareness of something in the environment the male
responds to stimulation, and the only reply we can give is that the
headquarters, or a distant song, or the proximity of another male--with
all of which, as we have seen, the instinct is definitely related--are
the specific factors which normally evoke response--and experience
teaches us that the periods of quiescence are just those when life is at
its lowest ebb and these stimulating factors less in evidence. Bearing
this in mind, bearing in mind the fact that when a male joins the flock
or crosses the boundary its instinct ceases to respond, bearing in mind,
that is to say, that there is evidence of relationship between these
specific factors and the song only when the territory is actually
occupied, the conclusion seems inevitable that we have here the
determining condition which renders the instinct susceptible to
appropriate stimulation.

There remains the female. I place her last in order of importance, not
because I regard her influence as of small consequence, but because the
evidence is of a varied and complex kind, so much so that it is
difficult to ascertain by observation just how far she is a situational
item. It will be remembered that the only direct evidence we had of such
influence was a deterioration or, in some instances, a complete
cessation of vocal manifestation. Clearly then we are confronted with a
relationship of a different kind from that which we have been
discussing; for not only is anything