Hoatzin! There was an old and tiny oxbow lake that had become swampy and was perfect habitat for a small family of hoatzins. Very ancient species of bird, really interesting.
The national bird of Guyana... I had at least a dozen sightings of Hoatzins over a period of approximately three hours. The birds were mostly rustling around within the canopies of the mangrove trees on the riverbank. Some of these groups of birds included juveniles. I was not able to capture any good photos due to the backlighting on the bank where most of the birds were to be seen...