MARSH WARBLER
of a jerk. On these occasions the song may gradually become more and more feeble until it develops into a quiet warble, audible only a few yards away and much like that of the Blackcap. Both sexes make use of a quiet note which is evidently a call, as it is used constantly by one or the other as they wander in search of food during periods of quiescence. The male has yet another method of expressing his emotion, which is peculiar and verges on the ludicrous. It generally occurs after he has been absent from the female for a time. Flying rapidly towards her and settling beside her, he concentrates all his efforts in violently producing a few bars of his song, and whilst doing so sways his body from side to side with his feathers tightly compressed, his bill pointing upward and widely opened, and his neck considerably stretched. A great part—perhaps the greater part—of the time which the male and female spend in close companionship is a tranquil one. It must not be supposed that the whole of the period of sexual activity, or even that the first few days of that period, is one of constant excitement. So far is this from being the case that if it were possible to estimate correctly the aggregate time during which emotional behaviour dominated the situation, it would be found to form but a very small part of the routine of their daily life. The outbursts of emotion are short, spasmodic, and irregular in occurrence, rather than constant or even prolonged; and it is difficult to say in which sex they are first aroused. Much, if not all, depends. I believe, upon the female in such matters. She is, so to speak, the medium by which Nature prevents a too liberal yielding to the sexual impulse; not, however, through the instrumentality of coyness, as suggested by Professor Groos, but rather by the aid of some physiological disposition which controls the sexual emotion. One sees the male approach the female in a manner which makes his intentions clear, and one sees her face him with lowered head and feathers erected, an attitude which makes her intention equally clear. One sees her, on the other hand,
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