The quick, musical drop of sound--a “stillicidious” note, my friend called it--was heard again. No; it was not from the sky, as we had thought at first, but from a thicket of alders just behind us. Then we recognized it, and laughed at ourselves. It was the staccato whistle of an olive-backed thrush, a sweet familiarity, over which I should have supposed it impossible for either of us to be puzzled. The star of the flock, as some readers will not need to be told, having marked the unexpected name in the foregoing list, was the Philadelphia vireo. What a bright minute it is in a man’s vacation when such a stranger suddenly hops upon a branch before his eyes! He feels almost like quoting Keats. “Then felt I,” he might say, not with full seriousness, perhaps,-- “Then felt I like some watcher of the skies When a new planet swims into his ken.” Yet how unconcerned the bird seems! To him it is all one. He knows nothing of his spectator’s emotions. Rarity? What is that? He has been among birds of his own kind ever since he came out of the egg. Sedately he moves from twig to twig, thinking only of another insect. This minute is to him no better than any other. And the man’s nerves are tingling with excitement. “You will hardly believe me,” said my companion, who had hastened forward to look at the stranger, “but this is the second one I have ever seen.” But why should I not believe him? It was only my third one. Philadelphia vireos do not feed in every bush. Be it added, however, that I saw another before the week was out.