Page:The British Warblers A History with Problems of Their Lives - 7 of 9.djvu/59

 in the lives of other species. What place are we to assign to song in the sexual process? In the life of the Willow Warbler I suggested that it might be of some use in connection with the territory, and the means whereby the females are made aware of the presence of males fit to reproduce. But supposing we say that song has a meaning in relation to something in the sexual environment of the female; supposing, that is to say, that her instinctive sexual response will only follow a certain presentation—a necessary part of which is formed by the song—how shall we explain this marked diminution of the song before coition has taken place, and before therefore the utility we postulate can possibly have come into play? Even the gradual slackening of the songis, in accordance with this view, not altogether easy to understand; for may it not be argued that a waning sexual instinct would require an even more vigorous presentation to arouse the necessary response, and that as the period of sexual activity progressed so the intensity of the song ought to increase rather than diminish? And yet the converse may be said to be possible, namely, that a response once aroused would be more readily awakened on subsequent occasions.

There is a point with regard to the sexual behaviour which deserves mention. I became acquainted with this species in Holland before I had an opportunity of doing so in this country, and I was there impressed with the attitudes the males habitually assumed, with, in fact, the intensity displayed in overt expressional movement. Of these attitudes the most striking was that one in which the wings were rapidly raised above the back and as rapidly closed, and has already been referred to. I therefore expected to find that the attitudes assumed by the males in this country would be similar to those already observed, but this expectation has not altogether been fulfilled. How far failure has been due to insufficient observation is difficult to say, but the way is clearly open to error, since we can never be quite sure that the conditions under which we observe different individuals entirely