Steatornis – Oilbird

The main food item in the chick's diet is palm fruit; due to this oily diet, they were once caught and boiled as lamp oil

Unlike most other nocturnal avians that primarily feed on insects, the Oilbird is frugivorous, depending mainly on the fruits of oil palms and other tropical plants for sustenance. The lipid-rich fruits are so integral to their diet that they have been named “Oilbirds,” reflecting the high oil content of the seeds they consume. This diet is also the source of another common name for the bird, “guácharo,” which means “one who moans” or “one who wails” in an indigenous Venezuelan language, referring to the bird’s eerie nocturnal calls.

The Oilbird has evolved several adaptations to thrive in its nocturnal niche. Their eyes are among the most light-sensitive of any bird, allowing them to see in near-total darkness. This is complemented by an acute sense of smell, which is uncommon among birds and is vital for locating their fruit diet in the dark.

Perhaps one of the most remarkable traits of the Oilbird is its use of echolocation to navigate within the pitch-black environments of its cave roosts. While echolocation is well-known in bats, the Oilbird is one of the very few birds that use a similar system. They emit a series of clicking sounds that bounce off the cave walls and obstacles, helping them to ‘see’ their surroundings through sound. This echolocation is not as sophisticated as that found in bats but is nonetheless effective for avoiding collisions in the dark.

When foraging at night, Oilbirds fly out of their caves, using their keen vision and sense of smell to locate fruit-bearing trees. They have a particular fondness for the fruits of the oil palm, which provide the high energy content needed to fuel their nocturnal lifestyle.