BRITISH WARBLERS
carried as he bends low upon the branch. During the pursuit a note is uttered which, as far as my experience goes, is peculiar to this particular moment, and after the proceedings have terminated the male shows evident signs of exhaustion, for he remains panting upon a branch with his bill wide open. The whole behaviour is strikingly similar to that of the Willow Warbler at a corresponding period. If there is any distinction between the two sets of behaviour, it must be sought in the degree of expansion of the wings, which after all is little enough, for the quivering may develop into flapping or the napping subside into quivering; and though experience betrays other differences of minor importance which enable us to distinguish the one bird from the other, yet for purposes of comparison we are justified, I think, in speaking of the behaviour as similar in both cases. There is one other interesting feature. The females of most of the Warblers occasionally assume, during the period of sexual activity, attitudes which are characteristic of the male, but the females of these two species, the Wood and Willow Warbler, are as persistent, or nearly so, in their wing flapping as the males, and not only are their actions similar to those of the male, but there is also a very general resemblance in the intensity of the emotional manifestation.
As far as my experience goes the female completes the nest without assistance from her mate, the work of construction occupying three or perhaps four days, but she does not labour throughout the day, fetching and fixing materials; if she did so the nest would probably be ready to receive the eggs by the evening of the first day. What happens is this, that at certain times she is seized with an impulse, which may last fifteen minutes or more, to build, and during that time she devotes the whole of her energy to the task. Flying backwards and forwards to some spot, a few yards away from the position selected, she carries leaves at one moment, a piece of decayed grass at another, fixes them rapidly,
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