The fact that many young birds which are quite helpless are now reared in nurseries on the ground, as in the case of young skylarks, is a fact of interest; for it shows that the parents have chosen this nesting site comparatively recently, and are of course unable to lay large eggs, which shall produce active young, like young chickens, at will. They have acquired the habit, so to speak, of laying small eggs, and cannot alter it by changing their nesting-place.