While examining the nest we hear at our very feet the terrible night noise—the muffled choking sigh which has come to us every night since we entered the mangrove wilderness. We are standing in our narrow dug-out, which the least movement will overturn, and for an instant it is indeed a question whether we can control ourselves enough to keep it from filling. Now the mystery solves itself as a large anaconda (_Eunectes murinus_) nine or ten feet long, slowly winds out from a hole in the bank beneath the surface of the water and slips into the depths of the muddy current. Then the tide laps a little lower, and a big bubble of air, caught in the entrance of the serpent’s lair, frees itself with a sudden gasping sob. When the tide is rising or falling over these large openings in the mud, the air escapes from time to time with the terrifying sound which has so long puzzled us. Our mysterious nocturnal creature is thus explained away in the prosaic light of day. [Illustration: FIG. 12. SOLUTION OF THE MANGROVE MYSTERY—AN ANACONDA.] An hour later as our dug-out rounds a sharp bend in the caño, there comes to our ears a series of rasping cries—hoarse and creaking as of unoiled wheels. The glasses show a flock of large, brown, fowl-like birds in a clump of bushes overhanging the water. Their barred wings and tall, delicate crests tell us that they are the bird of all others which we had hoped to see and study. We are floating within a hundred feet of a flock of Hoatzins[11]—the strange reptile-like, living fossils which are found only in this part of the world, and which are closely related to no other living bird. [Illustration: FIG. 13. HOATZINS IN THE BAMBOOS ON THE GUARAPICHE.] As we draw near, the birds flutter through the foliage as if their wings were broken. We find that this is their usual mode of progression, and for a most interesting reason. Soon after the young Hoatzins are hatched and while yet unfledged they are able to leave the nest and climb about the branches, and in this they are greatly aided by the use of the wings as arms and hands. The three fingers of the wing are each armed with a reptile-like claw, and at the approach of danger the birds climb actively about like squirrels or lizards. It has usually been thought that when they grow up they lose all these reptilian habits and behave as conventional feathered bipeds should. But we find that while, of course, the fingers are deeply hidden beneath the long flight-feathers of the wing, yet these very feathers are often used, fingerlike, in forcing aside thick vines, the birds thus clambering and pushing their way along.