In the yearly submerged gapo forests and the plains of the Upper Amazon, a singularly deep and long-sustained flute-like sound is often heard. It might be supposed that it was produced by the pan-pipes used by the natives of that region. It is, however, the note of a bird, named by the Indians _uira mimbeu_, or fife-bird, from the peculiar tone of its voice. It is, from the ornament on its head--consisting of a crest, with long curved hairy feathers, having long bare quills; which, when raised, spread themselves out in the form of a fringed sunshade over the head--called the umbrella-bird (Cephalopterus ornatus). It resembles in size and colour the common crow. In addition to this umbrella-like ornament on its head, it has what may be called a pelerine suspended from the neck, formed by a thick fan of glossy steel-blue feathers which grow on a long fleshy lobe or excrescence. This lobe is connected with an unusual development of the trachea and vocal organs, undoubtedly assisting the bird to utter its strange note. While singing, it draws itself up on the bough, spreads widely out the umbrella-formed crest, waves its glossy breast lappet, and then, in giving vent to its loud, piping note, bows its head slowly forward. The female has only the rudiments of a crest and lappet, and is of a much duller colour than the male. THE COCK OF THE ROCKS. Among the forest highlands at the foot of the sierras to the north of the Amazon, the magnificent orange-coloured cock of the rocks enjoys existence. About the size of a pigeon, it belongs to the tribe of the diminutive manakins, most of which have beautiful and curious plumage. It, however, surpasses them all. It has gained its name from the slight external resemblance that it bears to the gallinaceous form. Its plumage is of a rich orange tint; with the exception of the quill-feathers of the wings, which are of a sooty black hue, and those of the tail, which are brown tipped with yellow. On its head it wears a peculiar fan-like crest, which, overhanging the forehead, extends to the back of the head, and which bears a strong resemblance to the plume of an ancient helmet. The tips of these crest-feathers are tinged with brown and yellow. Between the wing and upper tail-coverts appear flowing plumes, which droop gracefully over the firmer feathers of the tail and sides. Like some birds of paradise in the Eastern Archipelago, the cocks of the rocks assemble in numbers to perform a kind of dance for their amusement, selecting generally the smooth rocks or roots of trees,-- moving here and there, round and round, backwards and forwards, and erecting their gorgeous plumes, to exhibit their beauty. Wallace observed a company of birds engaged in this singular way, though he says that no females or young birds were present.