Oilbirds, also called guácharos, are medium-sized nocturnal birds living in caves of South and Central America. They are a cinnamon-brown color with white spots on their chest and wings. These birds act like bats in more ways than one. First of all they live in colonies in caves. They are also nocturnal and use echolocation to find their way around. These animals got their name from the fact that natives where these birds live used to catch oilbird chicks and boil them to get an oil for cooking. Because they have short legs, oilbirds do not sit like most birds, with their back at a steep angle. Instead they sit so that their head is at the same level as their tail or even lower. This type of sitting can be seen in the picture above. Around their beaks, oilbirds have several bristles that can be up to two inches (5 cm) long.


Adult oilbirds measure up to 19 inches (49 cm) long from beak to tail. They also weigh up to one pound (455 grams) and have a maximum wingspan of 37.5 inches (95 cm).


Oilbirds are the only nocturnal birds that fly and eat fruit. The kakapo is nocturnal and eats fruit but cannot fly. Owls are nocturnal and can fly, but do not eat fruit. There are also many birds that fly and eat fruit but are not nocturnal. Because these animals do not have strong feet, they were created with the ability to hover in mid air while picking fruit off trees. Due to their large mouth, they can eat fruit as large as 2.3 inches (6 cm). Even fruits with pits do not stop them as they, like owls, will regurgitate any indigestible parts. Oilbirds use their senses of sight and smell to find their food and may travel up to 45 miles (75 km) in one night in search of food. Despite all of this wandering, they return home to the same place each night.

Habitat and echolocation

Although echolocation is not used for finding food, it is used to prevent the birds from running into cave walls. Oilbirds can live up to 2/3 miles (1 km) underground where little if any light can penetrate. These caves are also often in jungles or rain forests where trees also block part of the light. While using echolocation, oilbirds will emit up to 7,000 clicks per second. Unlike the echolocation of bats, these clicks are audible to humans.


The call of oilbirds is a rasping shriek that is used to communicate with other oilbirds. The largest colony of oilbirds in is Cueva de los Guacharos, a cave in Venezuela and contains in between 10,000 and 18,000 individuals.  The name of this cave means “Cave of the Oilbirds.” As you can expect with so many oilbirds squawking and using echolocation, it is very noisy. Click here to hear their call.


The oilrbirds’ nests are made of various things including fruit pits and bird droppings glued together with saliva. Sounds like a gross place to grow up.

Mating and eggs

Oilbirds are thought to be monogamous, remaining with the same mate for life. Several colonies will time their breeding season at the very end of the dry season, and many new chicks will be born within just a few days or weeks of each other. From two to four eggs are laid with an interval of two to five days in between each one. This means that they will all hatch at different times, therefore all of the chicks in one clutch will be different sizes. These eggs are glossy white when first laid, but soon become stained brown, maybe from the nest. Oilbird eggs are about 1.3 inches (3.3 cm) long and are rounded with a pointed smaller end.


After a 32-35 day incubation period, the eggs hatch, all at different times. The young are born with no feathers, closed eyes, and a pinkish skin. They are fed regurgitated fruit by both parents and after seventy days of a large amount of food, they are very fat and can weigh one and a half times as much as an adult! Despite being so heavy, they do not have a wingspan or body length the same size as an adult. After a while though, they are not fed as much and and more energy is spent growing, bringing their weight down. If lucky, these animals can live for up to 25 years.

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Photo credits:

  • Oilbird – Soerfm
  • Mystery animal – KENPEI
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