BRITISH WARBLERS
tion or thick foliage, and therefore might readily escape detection. In fact it is necessary to rely to some extent on the behaviour of the male in order to assure oneself of her presence, so that to observe her plucking the first piece of decayed vegetation with which to form the foundation of her nest is no easy matter. The male takes but a small part in the actual construction of the nest, his behaviour being in this respect similar to that of the male Reed Warbler, who labours but little to obtain the necessary material and weave it into the nest. But although he seems unwilling to share this work with his mate, yet he takes great pains to follow her closely, whenever she is engaged in searching for material or in deciding the actual position the nest is to occupy. In thus accompanying her closely when at work he resembles not only the male Reed Warbler but the males of other species also; and this habit of keeping a close attendance upon the female, of following her from tree to tree and bush to bush, desirous apparently of being a spectator of all her work and acquainted with all her movements, must be sexual in origin. After the nest has been built and laying has commenced the peculiarity is not so striking; true it is that he can often be seen beside her, but the craving for her companionship does not seem to be then so pronounced. His actual conduct during these few days gives us some insight into the true meaning of this close companionship, for we can frequently witness those playful contests which we know to be characteristic of sexual activity. The responsibility for these contests does not always rest with the male, but there is no doubt that we can more often mark their beginnings in him, although at times they seem to be almost mutual. One sees on such occasion a spreading and raising of wings on the part of one of the sexes, followed by a flying together and a touching of bills, accompanied by an uttering of the call note or a few phrases of the song. Of the two the male is more frequently the one that quivers his wings, and on his approach the female is sometimes accustomed to spread her tail and
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