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.
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, he 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
