I have observed the wandering bands only in Patagonia, where they are on a very small scale compared with those of the tropical forests. In the Patagonia thickets the small tit-like creeper, Laptas-thenura, is the prime mover; and after a considerable number of these have gathered, creepers of other species and genera unite with them, and finally the band, as it moves through the thickets, draws to itself other kinds--flycatchers, finches, &c.--many of the birds running or hopping on the ground to search for insects in the loose soil or under dead leaves, while others explore the thorny bushes. My observations of these small bands lead me to believe that everywhere in South America the Dendrocolaptidae are the first in combining to act in concert, and that the birds of other families follow their march and associate with them, knowing from experience that a rich harvest may be thus reaped. In the same way birds of various kinds follow the movements of a column of hunting ants, to catch the insects flying up from the earth to escape from their enemies; swallows also learn to keep company with the traveller on horseback, and, crossing and recrossing just before the hoofs, they catch the small twilight moths driven up from the grass. To return to the subject of voice. The tree-creepers do not possess melodious, or at any rate mellow notes, although in so numerous a family there is great variety of tone, ranging from a small reedy voice like the faint stridulation of a grasshopper, to the resounding, laughter-like, screaming concerts of Homorus, which may be heard distinctly two miles away. As a rule, the notes are loud ringing calls; and in many species the cry, rapidly reiterated, resembles a peal of laughter. With scarcely an exception, they possess no set song; but in most species that live always in pairs there are loud, vehement, gratulatory notes uttered by the two birds in concert when they meet after a brief separation. This habit they possess in common with birds of other families, as, for instance, the tyrants; but, in some creepers, out of this confused outburst of joyous sound has been developed a. musical performance very curious, and perhaps unique among birds. On meeting, the male and female, standing close together and facing each other, utter their clear ringing concert, one emitting loud single measured notes, while the notes of its fellow are rapid, rhythmical triplets; their voices have a joyous character, and seem to accord, thus producing a kind of harmony. This manner of singing is perhaps most perfect in the oven-bird, Furnarias, and it is very curious that the young birds, when only partially fledged, are constantly heard in the nest or oven apparently practising these duets in the intervals when the parents are absent; single measured notes, triplets, and long concluding trills are all repeated with wonderful fidelity, although these notes are in character utterly unlike the hunger cry, which is like that of