BRITISH WARBLERS
development during coition. That these different actions of the male as well as the various degrees of activity which he exhibits are similar in origin must, I think, be admitted, whether we consider they have a meaning in relation to something in the external environment of the female or not. They indicate that highly excited condition of the nervous system which is the prelude to the actual discharge of the sexual function, and in the gentle quivering or the rapid fluttering of the wings we are but observing different stages in the sexual process. There is a tendency, generally speaking, for the intensity of the activity feelings to increase gradually until the culmination is reached, the final effort being productive of the most violent motor reactions, and, judging by behaviour, the first appearance of a female does not necessarily evoke the pairing hunger of the male in the highest degree. Some definite stage of development of the ovaries may be necessary before the female can adequately stimulate the sexual response of the male. Of the attitudes assumed by the female at this period there is little to be said, a partial spreading of the wings in sympathy with the excitement of the male being all that I have definitely observed.
On frequent occasions excitement is shown by the male, when in the presence or proximity of the female, by an excessive use of his vocal powers, and in most instances the cause can be traced to the presence of an intruding male or an individual of another species; yet there are times when he is alone with her and yet warbles excitedly for a few moments in succession, and even picks up and carries decayed vegetation of some description. Concerning the song at this period, the most noticeable feature is its gradual decrease after the appearance of a female. Previous to this the male sings incessantly, usually from some tree or group of trees prominent in his territory; but this phase of his behaviour undergoes a distinct change upon her arrival. Periods of greater or less duration are then passed in complete silence, and it is difficult to resist the conclusion that his comparative silence is in some
10
