cess. This being
so, we ask, in the first place, whether the female, too, may not have an
eliminating test to pass; and in the second place, whether she may not
also assist in furthering the biological end of securing the territory.

Now the answer to the first of these questions will be found to be in
the affirmative. Just as, in the securing of a territory, the ultimate
appeal is to the physical strength of the male, so, in the course of her
search for a mate, the female may be called upon to challenge, or may be
challenged by a rival, and the issue is decided by force. My attention
was first drawn to this fact by a struggle between two female
Whitethroats, which I have described elsewhere. The scene of its
occurrence was the corner of a small osier bed occupied by one male, and
the females that took part in it had only recently arrived, but the
male, an unpaired bird, had been in possession of its territory for some
days. The sequel to this struggle, which was protracted and severe, was
the disappearance of both females, the male being left without a mate
for a further ten days.

[Illustration: Emery Walker ph.sc.

The female Chaffinch shares in the defence of the territory and attacks
other females.]

Numerous instances have since come under my notice. Hen Chaffinches
become so absorbed that they fall to the ground and there continue the
struggle. Seizing hold of one another by the feathers of the head, they
roll from side to side, and then, without relaxing their grip, lie
exhausted--the quickened heart-beat, altered respiration, tightly
compressed feathers and partially expanded wings betraying the intensity
of the conflict.

As the breeding season approaches, hen Blackbirds grow more pugnacious.
Individuals that early in the year have frequented the same spot daily
and have even shown every sign of friendship, become openly hostile. For
two years in succession I had an opportunity of observing females under
such conditions, and of studying the gradual change in their
relationship. Each morning at break of day and for some hours afterwards
they could be seen in the same place, one following the other as they
searched for food first in this direction and then in that, as if they
derived some special pleasure from the fact of their companionship. Then
a change began to manifest itself. Indications of animosity became
apparent; one would run towards the other in a threatening attitude and,
in a half-hearted man