The common potoo, is one of seven species of bird 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. It has a haunting melancholic song, dropping in both pitch and volume. When seized, this bird produces a squeaky sound, not unlike that of a crow. This call greatly differs from that of much deeper and more dramatic northern potoo. Common potoos are 34–38 cm 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. common potoo is found in Trinidad & Tobago and every mainland South American country except Chile, though it has been recorded in that country as a vagrant. There it ranges from the Andes to the Atlantic Ocean. N. g. panamensis is found from eastern Nicaragua south through Costa Rica and Panama and west of the Andes from northwestern Venezuela through Colombia and Ecuador into northwestern Peru.
The common potoo is a resident breeder in open woodlands and savannah. It avoids cooler montane regions; it is rarely observed over 1,900 m above mean sea level even in the hottest parts of its range. It tends to avoid arid regions but was recorded in the dry Caribbean plain of Colombia in April 1999. It has many populations in the gallery forest-type environment around the Uruguayan-Brazilian border. A bit further south, where the amount of wood-versus grassland is somewhat lower, it is decidedly rare, and due west, in the Entre Ríos Province of Argentina with its abundant riparian forest, it is likewise not common.
The birds at the southern end of their range may migrate short distances northwards in winter. The potoo sits with its eyes open and its bill horizontal while awake, but if disturbed, assumes an alert “freezing” posture (flexibility). This entails sticking its beak vertically up in the air, closing its eyelids (through which it can still see via slits), and remaining still. If disturbed by larger animals, it may break its camouflage and try to chase the threat away.
If disturbed by a human being, its behaviors can be quite variable - quickly flying away, intimidation via beak-opening, or remaining still even when being touched. Common potoos are monogamous. After mating, the female lays a single white egg with lilac spots directly into the depression in a tree limb. Parents normally care for one egg at a time. The male and female alternate brooding the egg while the other forages for insects. They divide brooding time evenly.
