Page:The British Warblers A History with Problems of Their Lives - 7 of 9.djvu/63

 singing may occur when the male settles beside his mate and sways his body from side to side, or when with ruffled feathers he flies towards an intruding male. Now it is manifest that the stimulus which evokes these feelings is very different in these two cases. In the former it is the presence of a female, in the latter the presence of a male. May we not therefore infer that the feelings themselves are different in origin? In the former case it is not altogether clear what the emotion is which is set free. That the presence of the mate is desired is evident, and this could not well be associated with feelings otherwise than of pleasure; consequently we cannot be far wrong in assuming that the emotion is sexual in origin. In the latter case we see our way more plainly; for correlated with the vocal effort is a certain ruffling of feathers and spreading of the tail which we know to be often the prelude to a skirmish, and, arguing from our own standpoint, the emotion must be akin to anger and probably corresponds to the instinct of pugnacity. In the former case the feelings are evoked by a desire for the presence of a mate, in the latter by a desire for the absence of a male. A contrast is thus presented; yet the reactions are similar. The relation of attitude to emotion runs on parallel lines, but here the emotion is not quite so easy to diagnose. The peculiar jerking of the wings which is correlated with excited singing first deserves attention. It occurs when two males are in proximity to one another. The stimulus to the emotional behaviour is clearly the presence of the other male, but what the specific emotion is which is thus aroused we can never know by direct observation, and consequently must rely upon induction. The presence of an intruding male is generally a cause of suspicion to the owner of a territory; such presence is not desired, causes irritation, and must therefore call forth an emotion of a corresponding type. But the jerking of the wings may also occur when the male is seized with a sudden passion after conjugation has taken place. No intruding male is then at hand to cause irritation, but the female is only a few yards