Foraging trips can cover tens of kilometres. The bird hovers at a fruiting palm or Lauraceae tree, takes the fruit whole with a hooked bill, and swallows it; the seed is regurgitated later, often back at the cave, which makes oilbirds significant long-distance seed dispersers. Tracking studies have found individuals roosting away from caves in forest trees more often than expected.
Inside the cave they navigate by clicks, in the audible range, in the same manner as swiftlets. The clicks give coarse obstacle detection only; the very large, highly light-sensitive eyes do the work outside. Oilbird retinas have an exceptionally dense packing of rod cells.
The common name comes from the historical practice of collecting fat nestlings and rendering them into oil, described by Alexander von Humboldt at the Caripe cave in 1799. Colonies are concentrated in few sites, which makes local extinction possible even though the species is globally Least Concern.