BRITISH WARBLERS
in the dim morning light of a stoat-like animal crawling along the branches. This habit, whatever the origin, seems now to be an indispensable part of the courtship and is very strongly implanted in the male; for, before following the female, the leaf or piece of grass is searched for with impatience, as the female does not stop but calmly pursues her way, the result being that whatever he first gets hold of, and can conveniently carry, is sufficient for his purpose.
In referring to this period of the bird's life. I have used the simple term "courtship" instead of the usual display followed by selection. Fascinated by a picturesque theory, I have, previous to this, attempted to interpret facts accordingly instead of being ad utrumque paratios, but closer study, devoted for some years to this courtship, convinces me that sexual selection as a rational explanation of the phenomena is impossible: the following reasons have been mainly instrumental in forcing this conclusion upon me.
Selection is impossible unless there are two or more males to be selected from.
I can find no evidence of this being a general rule in Nature, for although a second male occasionally approaches the zone of courtship and is consequently chased away by the first male, yet he is in no sense a rival, making no attempt to perform in the same extravagant manner; and if these two males were in competition for the female, and if such competition were to be decided solely by her choice, then, not only ought they both to display their plumage, but, unless the female is to be credited with sufficient mental power to enable her to carry, for her further consideration, the varying characteristics of each male in her mind, such display ought to take place simultaneously.
"If the male assumes these attitudes in order that the female may see him to the best advantage and thus be enabled to make her choice, then she ought to be watching him when thus occupied."
This is by no means the case, for she is generally walking,
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