Animals Wildlife This Bird With a Haunting Song Can Pretend to Be a Branch By Mary Jo DiLonardo Senior Writer University of Cincinnati Mary Jo DiLonardo covers a wide range of topics focused on nature, health, science, and anything that helps make the world a better place. our editorial process Mary Jo DiLonardo Updated September 06, 2019 The common potoo has a haunting song. julian londono/Flickr Share Twitter Pinterest Email Animals Wildlife Pets Animal Rights Endangered Species Potoos aren't the most beautiful birds. These nocturnal creatures have relatively nondescript ruffled brown feathers and rather big yellow eyes. The common potoo is found in southern Central America and the lowlands of northern and central South America, while the great potoo is found throughout Central and South America, according to the Cornell Lab or Ornithology. They may not be known for their looks, but potoo birds are known for their sounds. The common potoo often makes a haunting song composed of whistled notes that drop down in scale. The great potoo's call is a deep guttural series of squawks. Peru-based Rainforest Expeditions says, "This haunting noise has frightened many a guest, and even given rise to folktales!" A great potoo rests on a branch, blending seamlessly into the tree. Andrew M. Allport/Shutterstock But even more than what the potoo says is what the bird does when it's quiet. When the potoo is resting, it will often perch on a tree limb or fence post. With the combination of its distinctive plumage and it's ability to stay absolutely still for long periods of time, the bird blends into its surroundings, becoming well camouflaged, says the American Bird Conservancy. This blending ability helps protect the potoo from predators. In addition, the birds have another cool trick. Their upper eyelids have several small slits. That way, even when their eyes are closed, they have several tiny holes that allow them to peek out and keep an eye on potential predators.