The Guacharo trail leads down to a small river which flows down through a very deeply-shaded grotto with an adjacent rockface. Chestnut-collared Swifts nest on this rockface whilst the grotto itself contains a small colony of Oilbirds. This is the world's most accessible Oilbird colony & is one of the main reasons for the existence of the AWC as conservation body.
Oilbirds are large nocturnal fruit-eating birds which fly by echolocation. They eat mainly Oil-palm fruits & prior to leaving the nest youngsters are almost twice as heavy as adults as a consequence of massive amounts of body-fat. Amerindians harvested the youngsters which were killed & boiled to render their body fat which was used for cooking & to fuel lamps, etc.