Page:The British Warblers A History with Problems of Their Lives - 4 of 9.djvu/65

 Let me describe the behaviour of certain species when the sexual instinct is uppermost. Savi's Warbler, with outspread wings and tail, tumbles rather than climbs down the stem of the Arundo phragmites, and, upon reaching the mass of dead reeds at the bottom, follows, while slowly napping its wings, in the wake of the female. The Rook (Corvus frugilegus), lying upon the ground, expands its wings and flaps them slowly in a helpless manner. The Cormorant (Phalacrocorax graculus), while lying upon a rock, behaves similarly to the Book; extending its wings, it flaps them slowly, at the same time raising its outspread tail almost at right angles to its body. Numerous instances could be given showing that it is only necessary for circumstances of a sufficiently stimulating nature to arise in order that the corresponding activities should be produced, and in all such cases it is impossible not to be impressed with the very helpless appearance of the bird; it would, in fact, in some instances, be as easy, if not more so, to imagine the whole behaviour an act of simulation, than many of the cases which are unhesitatingly referred to that cause.

Now to all of this an objection may be raised on the ground that the one link necessary to complete the chain of evidence is missing—namely, that in no single instance is the same species mentioned as behaving in a similar manner, not only at the period in which the parental instinct is dominant, but also at other periods of excitement; and, while fully admitting the validity of such an objection, I shall reply to it as follows: Firstly, that if it could be shown that all the species, or even a considerable proportion of them, that behaved in the manner referred to when the nest was approached, behaved in the same way at other periods of excitement, if, for instance, the Avocet flapped its wings in a similarly helpless manner at the period of sexual activity, it would constitute proof, and, moreover, proof of a most conclusive kind, that the behaviour per se had no special part to fulfil. Secondly, that we are not wholly at a loss for the evidence that is