Oilbirds navigate, roost, and nest in dark caves. Unlike most birds, which navigate primarily by sight, oilbirds also have the unique ability to navigate using echolocation (also called sonar). While in the cave, echolocation enables the birds to avoid colliding with others in their colony. When they leave the caves to feed at night, they are able to avoid obstacles and obstructions.
While bats can detect objects the size of a gnat, oilbird echolocation skills are rudimentary. But they can detect objects greater than 20 centimeters (roughly the length of an adult human hand).
How does the echolocation work? Oilbirds emit short bursts of clicking noises, which bounce off of objects in the animals’ paths, creating echoes. The echoes return to the birds’ ears at different levels of loudness and intensity. The larger the object, the more sound waves that are deflected, making the echoes louder. This enables the birds to identify the size, shape, and location of the animal or object. What sounds like a single click to the human ear is in actuality an entire ‘burst’ of sonar signals. The oilbirds can thus receive constant spatial information from their surroundings, and can process this information much like the visual and audio sensations humans gather with our eyes and ears. This enables the birds to navigate at night without colliding into obstacles.
This summary was contributed by Victoria La Rocca.Edit Summary
“…oilbirds share with swiftlets (Collocalia spp.: Apodidae) the distinction of being the only birds capable of echolocation. These two species are among the very few vertebrates that echolocate with broadband clicks whose acoustic energy lies almost entirely within the human audible range, yet the structure of the oilbird’s syrinx is very different from that of swiftlets. A knowledge of the mechanism by which echolocative signals are produced will contribute to an understanding of the capabilities, limitations and evolution of avian sonar systems.” (Suthers and Hector 1985: 244)