Oilbird

En bref

Nocturne
  • Scientific Name: Steatornis caripensis
  • Spanish Name: Guácharo
  • Family: Steatornithidae
  • Known Nicknames: Guácharo
  • Average Length: 40–49 cm / 16–19 in
  • Average Weight: 350–485 g / 12–17 oz
  • Wingspan: 91–100 cm / 36–39 in
  • Key Feature: Large, hooked bill surrounded by long, stiff rictal bristles
  • Primary Diet: Frugivore (specialist feeder on oil-rich palm and laurel fruits)
  • Range: Northern South America (Colombia, Venezuela, Ecuador, Peru, Bolivia, Guyana, Trinidad) and Panama
  • Habitat: Caves and deep gorges in tropical montane and lowland forests
  • Social Structure: Highly colonial (nests and roosts in large colonies within caves)
  • Nesting/Breeding: Cave ledges and crevices (nest is a mound of regurgitated fruit pulp and droppings)
  • Statut de conservation : Préoccupation mineure (LC)
  • Évolution démographique : En baisse

The Oilbird (*Steatornis caripensis*) is a remarkable nocturnal denizen of South American caves, earning its name from the chicks' high fat content, which was historically rendered for oil and fuel. Resembling a large, rusty-brown nightjar with a wingspan of up to a meter, it sports a powerful, hooked beak fringed with stiff, whisker-like feathers that aid in navigating its pitch-black roosts. Its most unique feature is a sophisticated echolocation system, using rapid, audible clicks (unlike the ultrasonic calls of bats) to "see" in the dark, while its diet consists almost exclusively of oily palm and laurel fruits, which it locates by scent—an extremely rare ability among birds.

Faits amusants

The Oilbird is the world’s only nocturnal, fruit-eating bird that navigates deep caves using echolocation, but instead of the high-frequency clicks of bats, it produces sharp, audible clicks (around 7 kHz) that humans can easily hear. Its diet consists almost entirely of oily palm fruits, which it digests so efficiently that its chicks become so fat they were once harvested and boiled down for lamp oil—hence the name. To find these fruits, it can fly over 150 kilometers in a single night, using its exceptionally keen sense of smell, a rare trait among birds, to locate specific trees in the dark. And perhaps quirkiest of all: when startled in its cave, it emits a cacophony of eerie, rasping screams and wing-flaps that have been described as sounding like a demonic cackle, earning it the nickname “guácharo” (meaning “one who wails or laments”).

Habitats et répartition

The oilbird is strictly associated with cave systems in tropical and subtropical montane forests, where it roosts and nests in complete darkness, often in large colonies. These caves are typically found in limestone karst landscapes, deep gorges, or coastal cliffs, providing the stable, humid microclimate required for the species. Its geographical range extends from northwestern South America (including the Andes of Venezuela, Colombia, Ecuador, Peru, and Bolivia) eastward into the Guiana Shield and Trinidad, with isolated populations also recorded in Panama and on the island of Tobago. The oilbird forages nocturnally over adjacent forested areas, relying on the fruit of palms and laurels.

Comportements & Reproduction

Oilbirds are highly colonial, nesting in dense clusters within deep cave systems. Their social structure revolves around these colonies, where pairs likely form monogamous bonds for a single breeding season, though long-term pair fidelity is not well documented. Mating involves aerial chases and vocalizations within the dark caves, with the male courting the female at a potential nest site. A unique reproductive strategy is their exclusive reliance on echolocation to navigate the pitch-black caves to their nests, which are simple platforms constructed from their own regurgitated food, seeds, and feces. The female lays a clutch of just one to four eggs, but typically two, and both parents share incubation duties for about 32 days. The chicks are born altricial and are fed a rich, oily regurgitant of fruit pulp, a key adaptation for energy storage in a nutrient-poor cave environment. The young fledge after approximately 90 to 120 days, one of the longest nestling periods for any bird of their size, which helps them develop sufficient fat reserves to survive independently.

Alimentation

The oilbird is unique among birds for its strictly frugivorous diet, feeding almost exclusively on the fruits of oil-rich palms and laurels, such as those from the genera *Euterpe*, *Ocotea*, and *Nectandra*. Unlike most fruit-eating birds that digest only the pulp, the oilbird swallows fruits whole and later regurgitates the seeds, making it a critical seed disperser for neotropical forests. An astonishing fact is that it locates its food entirely by smell, possessing one of the most developed olfactory systems of any bird, which it uses to navigate through dense, dark forests at night. Furthermore, its chicks are fed these fatty fruits and become incredibly obese, weighing up to 50% more than adults, storing immense fat reserves that allow them to survive long periods without food if their parents are delayed.

Couleurs

The Oilbird has predominantly brownish-red or cinnamon-brown plumage, heavily mottled with black and white spots and streaks across the wings and back, providing excellent camouflage against tree bark and cave walls. Its underside is paler, with dark barring, and it lacks bright markings, but features distinctive, stiff, whisker-like facial bristles around its large, dark eyes.