Featured Family: The Oilbird (Steatornithidae)

The Oilbirds (Steatornis caripensis) are related to the nightjars but the nightjars and their relatives are insectivores while the oilbird is a specialist fructivore, and it is sufficiently distinctive to be placed in a family (Steatornithidae) and suborder (Steatornithes) of its own. That means the oilbird is the only member of the Steatornithidae family.

The caripensis of the binomial name means "of Caripe" referring to the mountainous Caripe district of Monagas, Venezuela, where Alexander von Humboldt first studied the species, and Steatornis means "fat bird", in reference to the fatness of the chicks. Oilbirds eat fruit that is rich in fat and oil (fruits of the oil palm and tropical laurels, and in Costa Rica has been reported eating aguacatillo). When chicks are fed these fruits before they are able to fly, they become very fat, often growing larger than the adults. Oilbirds got their common name from the fact that in the past chicks were captured and boiled down in order to make oil. In Spanish this bird is called guácharo or tayo, both terms of indigenous origin. In Trinidad it was sometimes called diablotin (French for "little devil"), presumably referring to its loud cries.

The oilbird ranges from Guyana and the island of Trinidad to Venezuela, Colombia, Ecuador, Peru, Bolivia and Brazil in forests and woodlands with caves. It is a seasonal migrant, moving from its breeding caves in search of fruit trees. It has occurred as a rare vagrant to Costa Rica, Panama and Aruba. In Panama, its rare but has been been reported regularly near the Canal Area, Panama City, Cerro Azul and Darién. They are colonial cave nesters, and so far a colony has not been found in Panama but it's suspected to exist somewhere in the Charges River Basin. 

They are nocturnal feeders, and as a matter of fact they are the only nocturnal flying fruit-eating bird in the world (the kakapo is also a nocturnal fructivore but flightless). They forage at night, with specially adapted eyesight. However they navigate by echolocation in the same way as bats. They produce a high-pitched clicking sound that is audible to humans.

Since oilbirds have short feet, they do not perch or stand on trees. Instead, the bird rests, which is like sitting. At rest, the head of the oilbird is lower than its tail. Furthermore, their feet are so weak that they do very little walking, instead they fly to get from one place to another.

This is a large, slim bird at 40–49 centimetres (16–19 in), with a wing span of 95 centimetres (37 in). It has a flattened, powerfully hooked bill (used to pluck fruit from trees) surrounded by deep chestnut rictal bristles up to 5 centimetres (2 in) long. The oilbird is mainly reddish-brown with white spots on the nape and wings. Lower parts are cinnamon-buff spotted with white. The stiff tail feathers are a rich brown spotted with white on either side. The feet are small and almost useless, other than for clinging to vertical surfaces. 

Important cave colonies are located in South America:

• La Cueva del Guácharo in Venezuela. Venezuela's first national monument which according to some estimates may have 15,000 or more birds living there. 
• Cueva de los Guácharos in Colombia. Colombia's oldest national park, located near the southern border with Ecuador in the departments of Huila and Caquetá.
• Cueva de los Tayos in the Morona-Santiago province of Ecuador.
• Dunston Cave, at the Asa Wright Nature Centre in Trinidad.