Watching the Hoatzins carefully with stereos for several evenings in succession we came to know and distinguish individual birds. Two, one of which had a broken feather in the right wing, and the other a two-inch short central tail feather, were excellent flyers and, taking their leaping start from the high branch, never failed to make their goal, going the whole distance and alighting easily. All of the others had to rest and one which was moulting a feather in each wing could achieve only about ten yards. This one fell one evening into the water at the second relay flight, and half flopped, half swam ashore. One evening a Hoatzin flew toward us and alighted near some hens on the ground, but took wing almost instantly back to his brush-wood. A day or two before we came one of the birds had used a beam of the porch as a perch. This general movement occurred at both sunrise and sunset and was always as thorough and noisy as we found it the first evening of our stay. For months, we were told, it had been kept up as regularly as clockwork. [Illustration: FIG. 152. (A) FEMALE HOATZIN FLUSHED FROM HER NEST; THE MALE BIRD APPROACHING.] In the morning as the sun grew hotter the birds became quiet and finally disappeared, not to be heard or seen again until afternoon. They spend the heat of the day sitting on their nests or perched on branches in the cooler, deeper recesses of their linear jungle. [Illustration: FIG. 153. (B) FEMALE HOATZIN IN THE SAME POSITION, THE MALE HAVING FLOWN NEARER.] The last view of them in the morning, as the heat became intense, or late in the evening, usually revealed them squatted on the branches in pairs close together. On moonlight nights however they were active and noisy, and came into the open to feed. The habit of crouching or settling down on the perch is very common with the Hoatzins, and it may be due to the weakness of the feet and toes. I am inclined however to consider it in connection with the general awkwardness in alighting and climbing, as a hint of the unadaptability of the large feet to the small size of the twigs and branches among which they live. Inexplicable though it may appear, the Hoatzin—although evidently unchanged in many respects through long epochs—yet is far from being perfectly adapted to its present environment. It has a severe struggle for existence, and the least increase of any foe or obstacle would result in its extinction.