During the day these gregarious birds rest on cave ledges. The nest is a heap of droppings, usually above water (either a stream or even the sea). The bird pictured is brooding a half-grown youngster.
The YOUNG become very fat before fledging, weighing up to half again as much as the adult birds do. In times past the Amerindians of Venezuela harvested the almost-fledged young which were killed & rendered by boiling to yield oil for lamps & cooking. The generic name Steatornis translates as "fat bird" referring to the oil-rich squabs.