eature of the territory, and exercises a
dominating influence on the life of the bird. I have referred to it as
the "headquarters," and it may be a solitary tree or bush, an
outstanding mound or mole hillock, a gatepost or a railing--anything in
fact that supplies a convenient resting place so long as it fulfils one
condition, namely that the bird when it is there is conspicuous. It need
not, however, be a tree or a mound or indeed anything upon which the
bird can perch, for there is reason to think that the soaring flight
undertaken at this season by so many males, since it is generally
accompanied by the specific sexual sound, answers the same purpose as
the topmost branch of a tree.

Now there is nothing in the external environment to which the song is
more definitely related than to the "headquarters"--this at least is the
conclusion to be drawn from the behaviour, and I will indicate the sort
of evidence upon which such conclusion is based. There is, first of all,
the persistency with which the male resorts to the same tree, even to
the same branch, and, as it seems, solely for the purpose of
advertisement. We know by experience the approximate routine of the
male's behaviour; we know where to seek it, where to hear it, and when
once we have discovered its headquarters, we know that there it will
sing day after day for weeks or it may be for months together--perhaps
the most striking feature of its behaviour at this season. Next, we find
that other trees, though made use of, are not made use of to a similar
extent for the purpose of song. The area occupied varies much according
to the nature of the environment; it is sometimes extensive, and seldom
less than half an acre or so in extent; but in most instances it
contains plenty of trees and bushes which could, one would imagine,
serve the purpose of a "headquarters" just as well as the particular one
selected, and yet the bird, when there, betrays no inclination to sing
at all comparable with that which can be observed when it occupies its
accustomed perch. Further evidence is afforded in the behaviour of those
species that make temporary excursions from their territories. The male,
on its return, flies as a rule direct to its special tree and sings.
Sometimes, however, it settles upon the ground, not unfrequently
accompanied by the female, and while there remains silent; but presently
rising from the ground and deserting its mate, it flies to the
headquarters and