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 As the eggs of a bird are stationary, and do not run away or seek shelter whilst the parent bird is thus behaving in their neighbourhood, it would, on the whole, be better for it to sit close or to fly away in an ordinary and non-betraying manner. Allowing this, then, as the eggs of a bird would be less exposed to danger the less often the sitting bird went off them in this way, might not natural selection keep throwing the impulse to do so farther and farther backwards till after the incubatory process was completed? Then the tendency would be encouraged—at least in the case of birds whose young can early get about—for, as a rule, such antics would shield them better than sitting still. The young would generally be in several places—giving as many chances of discovery—and, on account of the suddenness of the surprise, would often be running or otherwise exposing themselves. Take, for instance, the case of the wild-duck, where I have always found the brood a most conspicuous object at first, and taking some time, even on reedy rivers, to get into concealment.

And I can see no reason why an aiding intelligence in the performance of such movements should not be selected pari passu with the movements themselves, though of a nervous and, originally, purely automatic character. Natural selection would, in this way, develop a special intelligence in the performance of some special actions, out of proportion to the general intelligence of the creature performing them, though, no doubt, this also would tend to be thereby enlarged. And this is what, in fact, we often do see or seem to see. I may add that when, a few days afterwards, I again approached this same nest the bird went off it