BRITISH WARBLERS
consequently of the bearing it may have on the unknown connection between different individuals, or classes of individuals, which, if known, would go far to explain such incidents, and perhaps enable us to form a truer definition of species than hitherto possible.
The courtship commences directly the females arrive, about ten days or so after the males; and as the females at this period persist in skulking in the bottom of the thickest rushes and undergrowth, it is most difficult to see what actually takes place; but the glimpses I have occasionally obtained tend to make me look upon the males when in love as rather sober-minded individuals; although the females for their part insist upon very close attention, and a somewhat servile attitude on the part of their suitors. A male pursues the female with drooping wings and erected head-feathers, uttering a rather harsh call-note; sometimes when quietly following he picks up and carries a dead leaf. If another male approaches too closely he pursues him with quick, vigorous flight. The female all the time keeps up her gentle call-note, which becomes more vigorous if her suitor, while pursuing another male, is forgetful and leaves her too long alone. Sometimes the two play together, flying at one another, the male scolding; and again they will sit close beside one another, an uninteresting couple, except when the male runs up and down the branch sideways, as he frequently does, with drooping wings and tail.
The nest, placed low down amongst the thick tangled undergrowth in the fork of a willow, or on the low branches of a bramble, especially when the latter entwines amongst a thick growth of Juncus effusus, is built up as follows: The foundation is dead grass of various kinds mixed with small pieces of dead thistle; on this is a thick layer of the fluffy seeds of the various species of Salix, bound together with fine dried grass, the lining being usually of the latter substance only. The female does most of the building, flying backwards and forwards to the Salix nigricans, carrying billfuls of the seeds,
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