Of all the strange nocturnal sounds that surround visitors to the tropical forests of the Amazon basin, the call of the great potoo must rank among the most unusual and perhaps even unsettling.
Found throughout the tropical Americas, from southeastern Mexico to the Amazon forests east of the Andes, potoos are a genus of seven species of Neotropical bird. Potoos are related to nightjars and the intriguingly named frogmouth. Like frogmouths, potoos are characterized by their wide but rather truncated beaks, which when opened reveal disproportionately large mouths, or “gapes”.
Potoos are insectivores, although at least one member of the genus, the great potoo, will also hunt small bats. Potoos hunt at night by sallying forth from a perch, in the manner of flycatchers, and gathering their prey into their mouths. During the day, they perch upright on tree stumps, using their plumage as camouflage and aligning their bodies to make them appear like an extension of the stump. Having adopted this pose, they remain motionless and with their eyes half open, in order to avoid the attentions of potential predators.
Rather than building a conspicuous nest, which would be vulnerable to predators such as raptors and arboreal snakes, as well as some species of primates, potoos lay a single egg directly on top of the same tree stump they use for camouflage. The task of incubating this single egg is shared by both the male and female.
In addition to their sometimes disquieting call, across their seven species potoos are also notable for their unusual appearance. Potoos are blessed with mottled plumage in a range of brown, gray and whitish tones, perfectly adapted to enable them to remain totally camouflaged when at rest during daylight hours. Potoos range from around 21 to 58 centimeters in length (8 to 23 inches). They have disproportionately large heads, and their wings and tails are long. Their weak legs and feet are only used for perching. While its bill is broad, it hardly projects at all from the potoo’s face. But the potoo’s appearance is dominated by its enormous yellow eyes; indeed, some observers have described the overall effect of the potoo’s face as “Muppet-like”.
In common with many other birds –as well as other nocturnal tropical forest species such as caimans- potoos’ eyes reflect the light of flashlights, which because they are so well camouflaged is one of the surest ways of detecting their presence. In order to ensure that their massive yellow eyes will not give away their presence to predators during the day, potoos are equipped with slits in their eyelids, enabling them to detect movement even when their eyes are closed.
Because of their excellent camouflage and nocturnal habits, potoos are usually heard rather than seen. The wailing cry of some species, “po-TOO”, is what has given all seven species their onomatopoeic common name. The largest of the potoo species, the great potoo (Nyctibius grandis), also known as the grand potoo, has been described as producing a long “drawn-out moaning growl”. Its haunting call has given rise to forest legends. In some indigenous peoples’ stories, the eerie call of the great potoo is that of a rainforest spirit, crying out to the moon.