The common potoo, or poor-me-ones (Nyctibius griseus), or urutau is one of seven species of birds within the genus Nyctibius. It is notable for its large, yellow eyes and comically wide mouth. Potoos are nocturnal and are related to nightjars and frogmouths. They lack the characteristic bristles around the mouths of true nightjars. Taxonomy The common potoo was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it with all the nightjar like species in the genus Caprimulgus and coined the binomial name Caprimulgus griseus. Gmelin based his description on "L'engoulevent gris" from Cayenne that had been described from a preserved specimen in 1779 by the French polymath Georges-Louis Leclerc, Comte de Buffon. The common potoo is now one of the seven potoos placed in the genus Nyctibius that was introduced in 1816 by the French ornithologist Louis Jean Pierre Vieillot. The genus name is from Ancient Greek nuktibios meaning "night-feeding", from nux night and bios "life". The specific epithet griseus is Medieval Latin meaning "grey". The common potoo was formerly considered to be conspecific with the northern potoo (Nyctibius jamaicensis). The species were split by the American Ornithologists' Union in 1995 based mainly on the differences in vocalization. Two subspecies are recognised: N. g. panamensis Ridgway, 1912 – east Nicaragua to west Panama, west Colombia and west Ecuador N. g. griseus (Gmelin, JF, 1789) – north, central South America east of the Andes Description Common potoos are long with mottled red-brown, white, black, and grey cryptic plumage. This disruptive coloration allows the potoo to camouflage into branches. The sexes appear similar, and cannot be distinguished upon observation. The eyes can appear as giant black dots with a small yellow ring, or as giant yellow irises with small pupils due to voluntary pupil constriction. The potoo has two or three slits in the eyelid so that it can see when the eyelids are closed; these notches are always open. The upper and lower eyelids can be moved independently and rotated so that the bird may adjust its field of vision. The common potoo has an unusually wide mouth with a tooth in its upper mandible for foraging purposes. It has a haunting melancholic song, a BO-OU, BO-ou, bo-ou, bo-ou, bo-ou, bo-ou, bo-ou, bo-ou dropping in both pitch and volume. When seized, this bird produces a