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 leaving his own mate to guard their chosen ground; and instead of resenting this visit as an unwarranted intrusion on their domain, as they would certainly resent the approach of almost any other bird, they welcome it with notes and signs of pleasure. Advancing to the visitor, they place themselves behind it; then all three keeping step begin a rapid march, uttering resonant drumming notes in time with their movements, the notes of the pair behind being emitted in a stream, like a drum-roll, while the leader utters loud single notes at regular intervals. The march ceases; the leader elevates his wings and stands erect and motionless, still uttering loud notes; while the other two, with puffed-out plumage, and standing exactly abreast, stoop forward and downward until the tips of their beaks touch the ground, and, sinking their rhythmical voices to a murmur, remain for some time in this position. The performance is then over, and the visitor goes back to his own ground and mate, to receive a visitor himself later on."

Now the most curious point in this remarkable performance, so well described, is that three birds—a pair (male and female), and one other, whether male or female is not stated—take part in it, and how is this fundamental peculiarity to be explained better on the theory of "a universal joyous instinct" than on that of sexual selection, if, indeed, the former one helps us so well? Joy, no doubt, is there, but something else—some shaping force—is surely required to account for the particular form in which it finds expression. Now with regard to the peculiarity pointed out—the odd bird (though all act oddly)—I have, whilst watching birds in the early spring, been struck by the