Page:The Zoologist, 4th series, vol 6 (1902).djvu/178

antics) which immediately precedes the rolling, and which, also, cannot properly be separated from it. All this set of actions must be looked upon as so many parts of one and the same whole thing, and to explain such whole thing we must call in some cause which will equally account for all its parts. The deliberate intention of making a nest will not do this, for many of the actions noted do not in the least further such a plan. On the other hand, sexual excitation may just as well produce rolling on the ground (as indeed it does in some other birds^[1]), and perhaps, even, pecking round about on it, as it may the set, stiff run, and those other peculiar movements. And if some of many movements, the cause of all of which is sexual, should be of such a nature that out of them good might accrue to the species, why should not natural selection seize hold upon, increase, and gradually shape them, making them, at last (through the individual memory), intelligent and purposive, since, by becoming so, their utility might be largely increased, and proceed at a much quicker rate? I believe that in these actions of the Peewit—commencing immediately after the excitation of pairing, with a peculiar run (which, or something similar to which, may be observed in various birds), and going on, without pause or break, to other motions having the same plain sexual stamp upon them, though some may, in their effects, be serviceable—we see this process actually at work, and I believe, also, that in the nest-building of species comparatively advanced in the art we may still see traces of its early sexual or ecstatic origin. I have been, for instance, extremely struck with the movements of a hen Blackbird upon the nest that she was in course of constructing. I have not my notes at hand, but these movements appeared to me to partake largely of an ecstatic—one might almost say a beatific—nature, so that there was a large margin of energy over and above the actual business of building, to be accounted for. I was not in the least expecting to see this, and I can, perhaps, best estimate the extent of the thing by recalling how it surprised and struck me. The wings were half-spread out, and would, I think, have drooped,^[2] had not the edge of the nest supported them, and I particularly

1. Most notably in the Ostrich.
2. The drooping of the half-spread wings is very characteristic of sexual excitement in birds.