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 manner, peck at it; and gradually the hostility grew, until the tentative pecking developed into a scuffle and the scuffle into a conflict. Much fighting also occurs between the females of the Reed-Bunting, and likewise between those of the Moor-Hen, and because these two species are not only common but inhabit respectively open stretches of marshy ground or large sheets of water, the fighting can be readily observed. Why do the females fight before they are definitely paired? To obtain mates? This certainly seems to be the obvious explanation because any question of securing territory can be excluded; yet if it be true that their sex is numerically inferior, it is difficult to understand the necessity for such strenuous competition. But what is the condition under which the pugnacious instinct of the female is rendered susceptible to stimulation? It cannot be merely the presence of a male ready to breed, for then there would be endless commotion amongst the flocks of Chaffinches or of Lapwings which in March are composed of both sexes, including even males that have secured territories. There must be some other circumstance; and, judging by experience, it is to be found in the territory--a male, that is to say, in occupation of one, is the condition under which the inherited nature of the female is allowed free play. We must bear in mind, however, that the competition between the males is very severe, that large numbers probably fail to pass even this preliminary test, and that only a proportion are in a position to offer to the female the condition under which her process can successfully run its course; so that the presumption is--though it is incapable of demonstration--that there is a competition for such males each recurring season, and that, on the average, the weaker females fail to procreate their kind.