What shall we say about the bird's right to liberty? Clearly the bird at liberty to perform the part which Nature intended for him can fully accomplish that part only when at liberty to go his own way. But it would be idle to declare that the caged bird is in nowise useful to the world. There are some things which can be learned about birds only from caged ones. If a bird be caged for the purpose of learning these things the very few that will be needed for this purpose will be fulfilling a high good, and if given their freedom again when the lessons have been learned the harm, if there be any, will be fully repaid. But here, again, the caged bird will be the rare exception and so does not affect the right of the average bird to liberty. We then have only to inquire whether the bird has a right to the pursuit of happiness. No one who has studied the living bird with anything like an appreciation of it will think of denying that birds are creatures of intense life, capable of strong feeling and keen enjoyment. They speak out their feelings in song and action. It is really their human attributes which makes them appeal so strongly to us. We know that they are capable of love and hate, of joy and sorrow, of pleasure and pain. In them we recognize the heroic attribute of martyrdom. In order, therefore, to determine what the attitude of the bird would likely be were his right to the pursuit of happiness denied, we have only to ask what our own attitude would be under the same circumstances. If our happiness should be threatened in this place we would certainly go where it would not be. The birds do the same. But we have already seen that the birds have a right to life and liberty on account of the services they render to the world. If we deny them the right of happiness they will not be able to perform their service for us. Under persecution they cannot do their best, even if they remain to do anything for us. Persistent persecution will either drive them away or destroy them altogether. Since we cannot do without their services even for a single year, it is clear that we must agree that they do have the natural right to the pursuit of happiness. We are ready, then, to concede to the birds as natural rights what we long ago declared were the natural rights of mankind,--"Life, Liberty and the Pursuit of Happiness." We might properly discuss the question, What do we owe to the birds? but that is a separate topic for a later time. STRUCTURE AND HABITS OF BIRDS. From a lecture by Frank M. Chapman, April, 1900.