The oilbird, also known as the guácharo, is a cute, chonky bird distantly related to the nightjar; while the nightjar went for a dragon-ish look, the oilbird looks more like an owl trying for a supersonic-flight build. It is best know for being one of the few bird species to use echolocation to navigate.
Oilbirds live in northern South America (primarily Colombia, Peru, Ecuador, Bolivia, Guyana, and Venezuela) and the island of Trinidad. They live in neotropical mountain forests, primarily in the Andes, nesting in breeding colonies in caves or cliff faces, although non-brooding birds will also sometimes roost in trees to extend their foraging range. Colonies consisting of up to 18,000 individuals have been found, although most are much smaller, dozens or hundreds of birds in size. They are nocturnal, coming out at night to search for fruit, and may travel quite far to scavenge, with 150 kilometers appearing to be within the means of many a bird. As habitat loss and deforestation has forced birds to travel further to find food, we don't have a clear idea of what the default range of these birds may have been.
Oilbirds are so named because locals used to (and sometimes still may) harvest them for the oil rendered from their fat. The birds eat palm oil fruit, small avocados, and other oil-rich plants, and thus are a good source of fat themselves. Traditionally the young are harvested sometime around April, with hundreds being taken from larger colonies. As far as I can find, the young are targeted specifically because they can not fly away when knocked out of their nests by the long sticks carried by hunters, and not because they were exceptionally fat. However, it is somewhat difficult to find details on oilbird rendering.
Every oilbird website on the entire internet wants to make the point that they are the only flying nocturnal fruit-eating bird. The multiple qualifiers are necessary; the kākāpō is also a nocturnal fruit-eating bird, but is flightless. For my money, it is a much more interesting fact that there are only a few species of birds that use echolocation: the oilbirds and a couple of species of swiftlet.
The oilbirds make a lot of noises: loud snarls and snoring sounds, apparently used to mark territory; more frequently they use harsh screams and screeches; and most interestingly, they will emit pair of sonar clicks, perfectly audible to humans, although occurring so closely together than they sound like a single click. These bursts last for 40-50 ms, and generally fall in the range of 1.5 to 2.5 kHz -- which is to say, they are perfectly nondescript and unremarkable. These clicks are used to help the birds navigate through the caves an rocky terrain at night, and become somewhat redundant out in the open, as the olibird has excellent night vision and a well-developed sense of smell. The olibird's echolocation is almost certainly entirely an adaptation to living in caves, stone being a better reflecting surface than fruit or trees.