Apparently Hoatzins can be reliably found at this spot.
Hoatzins are arguably the strangest bird species there is. They are just over two feet long and funny looking—bare blue face, bright red eye, wild spiky crest. They have strange, unique, habits—they eat mostly leaves, unlike most birds. They have an enlarged, two-chambered crop in which bacterial fermentation of their food occurs. This is sometimes likened to the ruminant digestive system. Because of this they are said to have a manure-like odor, and are also reputed to taste bad, and have never been hunted. Chicks are fed by regurgitation of the fermented food. Uniquely among birds, the chicks have two Archaeopteryx-like claws on each wing, with which they can clasp twigs and climb around in brush near the nest for the 60–70 days that it takes for them to be able to fly. Eventually the claws are lost.
It remains a mystery what other bird species the Hoatzin is most closely related to. Recently they have been considered to be related to seriemas, turacos, or cuckoos, or doves. Historically, they have also been considered related to tinamous, galliformes, rails, bustards, sandgrouse, or mousebirds. Basically, nobody has any idea. The latest classification, which has been in the news lately, has them as the sister group to Charadriiformes and Gruiformes.
So it was truly special to be able to see this unique bird in the wild.