Such observations as the one noted in detail I have so frequently repeated with widely-differing species as to satisfy me that what may be termed "direct instruction" in flight is given to the young birds by their parents. "Indirect instruction" also is noticeable, in the fact that the parent-birds cease to feed their young, and so force the latter to leave the nest and follow them. Once out of the nest, they soon endeavor to walk on air, as it were, and, falling, open their wings, and, as described, thus take the initial step. This ceasing to bring the food to the young while yet in the nest is done in some instances, I judge, only to draw them from the nest; and then they feed them as before, but not as frequently, which leads the young to voluntarily move from point to point. The important fact must not be lost sight of, too, that the young birds, when once out of the nest, witness nearly every movement of their parents, and learn, undoubtedly, very much through imitation of their movements.
For these reasons, I believe the acquisition of full flight-power is gradually acquired; first there is a mere "flapping" to prevent falling; then short horizontal stages of aërial progression; finally, a steady, intelligent use of the wings, enabling the birds to execute the highest type of flight within their capabilities, i.e., upward flight.
In the case of birds of more complicated flight than those mentioned above, such as the falcons, where hovering is a necessary acquirement, the truth of the assertion that flight is gradually acquired becomes more evident from the fact (which I have very frequently verified by observation) that the young birds for some time after leaving the nest are fed by their parents. They commence procuring food for themselves by chasing sparrows; checking their moderate flight when above a thicket, they rush upon the fleeing birds, more frequently without success than with. Their first attempts at hovering are miserable failures, and it is not until autumn that they are enabled, by the complete control of their wings, to stay themselves in mid-air, and, at the proper moment, dart with unerring aim upon some luckless mouse.
I have used the term "unerring," because it is customary so to characterize this act of the falcons; but, having watched, with a powerful field-glass, the hovering and darting of hawks, I have been forced to consider the term far from correct, and that not more than one-half, if as many, of the "strikes," on the part of the bird, are effectual.
Following the young birds, of any species, from the nests, and noting their movements, we find that the one prominent aim of their lives, during their first summer, is the acquisition of food. They have really nothing else to do, if we except escaping from the attacks of their enemies, and this is taught them directly by their parents. I judge that the great majority of birds that fall victims to birds of prey and carnivorous mammals are young. To return to the feeding-habits of birds. These appear to be acquired, by every bird, through
