BRITISH WARBLERS
attention solely owing to the size of the bird and the conspicuous colouring of the plumage, but in the case of the Blackcap, and also of many other of our most common native species, the conditions are entirely reversed, for they are small, their plumage is inconspicuous and dull, their performances are more quickly executed, and consequently very close attention to their habits is necessary, in order, not only to see, but to realise what is actually taking place. Yet their antics are no less remarkable. The difference is only one of degree, not, however, in the performance, but in the plumage. Imagine the Blackcap possessed of the gorgeous plumes of many other species, and his exhibition would be a truly remarkable one. During this time of excitement the feathers on the head, especially the black cap, are raised, but sometimes alternately raised and lowered, those on the breast and flanks are fluffed out and the throat is often distended, but more particularly so when singing. The feathers on the back are raised disproportionately, giving one the impression that one or two of the longer ones were being moved independently of the others, the wings are drooped or extendedfully and flapped, the scapulars raised, the tail-feathers quickly spread out and as quickly contracted, and the tail itself either raised or lowered at various angles. The tail is often spread out to such an extent that large spaces appear between the different feathers, and is sometimes carried at right angles to the body. When the flapping flight is in progress the wings are fully extended, and as far as it is possible to tell, the feathers all over the body are relaxed.
We now come to the part played by the vocal powers in the courtship. According to the theory of sexual selection, song has been developed in the males owing to the females being more sexually excited by, and consequently pairing with, those whose vocal powers were developed in the highest degree. The male Blackcap is one of the most beautiful—and in the opinion of some, the most beautiful—of our native songsters. His rich and liquid notes will bear com-
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