are the strong lure, the talisman, the magnet to which the parent is irresistibly drawn. The tree, the branch, the nest itself, what are these in comparison with the young for whom only they exist? This is true notwithstanding the fact that birds will sometimes leave their young to perish while they start on their migrations. As a rule they follow one line of conduct until their instinct in this direction has been satisfied.
With some species it is possible to make the necessary change without evil consequences when there are eggs in the nest: with others we must wait until the young are from four to nine days old. It is all a question of the strength of the parental instinct, and this varies between wide limits in different species, and very considerably between different individuals. From the nature of the case there can be no infallible rule. If we know little of the habits of the bird in question, it is safest to wait until the seventh to the ninth day after hatching, or when, as in many of the common passerine birds, the feather-shafts of the wing-quills begin to appear, or, better, when they project from one-quarter to one-half inch beyond the feather-tubes. At this period the parental instinct is reaching its maximum, and, what is equally important, the sense of fear has not appeared in the young.
Young birds from one to five days old as a rule cannot stand excessive heat. Even when fed and brooded they will sometimes succumb, and here lies the serious danger to be guarded against. A nest of very young birds well shaded by foliage cannot be safely carried into the direct sunshine of a hot summer's day, hence the importance of beginning operations at the proper time when the weather is suitable, and further of not allowing your enthusiasm to get the better of your judgment.
The young may be handled or fed as much as one wishes, provided they have not acquired the instinct of fear. If you are uncertain as to this, and your aim is to study the nesting habits, it is better to avoid approaching, touching or in any way disturbing the young after the flight-feathers have appeared. The cutting of leaves or twigs which obstruct the light or cast undesirable shadows should be done before this time.
Young birds eight or nine days old stand the heat well, provided they are fed, but on very hot days they should not be allowed to go without food for more than two hours at the longest. Should the parents bring no food during this time, it is better to feed the young in the nest, and to suspend operations until the next day.
The old birds may be expected to come to the nest in from twenty minutes to an hour, when the tent is brought into use immediately after the removal of the nesting bough. It is naturally impossible to predict exactly what will happen until the experiment is tried, since
