The Super Senses of the Oilbird Inspire Scientists

In addition to its extremely sensitive vision, the oilbird has the neural foundation for an excellent sense of smell, bristles by the beak for tactile sensation and it also uses its hearing for echolocation, which we find otherwise pretty much only in bats and toothed whales.

- This complex sensory apparatus, where the animal has the ability to combine input from so many well-developed senses, is interesting to study, says Signe Brinkløv, postdoc in the Sound, Communication and Behaviour Group at the Department of Biology, University of Southern Denmark.

As a biologist, she is interested in understanding how the oilbird uses its senses to achieve the best possible conditions in its natural surroundings.

- We can come a long way towards understanding the individual sense. But when we begin to study how the senses complement each other and how the balance between different sensory inputs affects the behaviour of the animal when it tackles various challenges, it becomes a very complex study, which is difficult to transfer from laboratory to natural conditions. If we can learn more about it, perhaps we can transfer the knowledge to technological developments, she says.

An example is the interaction between vision and the sense of hearing, which the animal uses when it echolocates.

With echolocation, the animal emits sounds that are returned as echoes from the surroundings and enables it to judge for example distance to the surroundings or distinguish between, e.g., food items and a rock face.

Today, drones are often controlled manually by a drone operator who is dependent on the video footage from the drone and thus the sense of sight in order to control it. But it quickly becomes difficult to navigate with such a system in darkness or when visibility is poor. If, on the other hand, you could combine the sense of sight and echolocation on a drone so it navigates based on input from both systems, then more opportunities open up. For instance, it could fly safely and perhaps autonomously in the dark or in between trees in a forest, says Signe Brinkløv.

Signe Brinkløv and her colleagues have studied the echolocation of oilbirds in Trinidad. Oilbirds are nocturnal and live in caves with up to several thousand individuals together. Every night they leave the cave to find food.

Their ability to echolocate enables them to navigate to and from their nests without bumping into the rocky walls of the cave, even in pitch black darkness.

The researchers hope that with further studies of the oilbird which investigate the interaction between vision and echolocation, a model can be developed that can be used by sensory researchers and robotics engineers.

The study is based on sound recordings of echolocating cave-dwelling oilbirds at Asa Wright Nature Centre, Trinidad. The study has been published in Royal Society Open Science. The authors are Signe Brinkløv, Coen Elemans and John Ratcliffe.

Signe Brinkløv is a biologist at Department of Biology. Apart from birds, she also studies porpoise and bat communication.

The oilbird (Steatornis caripensis) got its name because the fledglings, just before leaving the nest, become so fat that their weight exceeds that of the adults. Just like whales, oilbirds have been used in the past for extraction of oil. Oilbirds also produce other sounds than their echolocation signals which has led to several Spanish nicknames, including Guácharo and Diablotin (little devil), reflecting ghostly sounding calls which led the local Indians to compare the entrance to the birds’ caves with that to the land of the dead.

Citation: Oilbirds produce echolocation signals beyond their best hearing range and adjust signal design to natural light conditions, published in Royal Society Open Science by Signe Brinkløv, Coen P. H. Elemans, John M. Ratcliffe
Published 24 May 2017.DOI: 10.1098/rsos.170255