How do oilbirds navigate through caves in complete darkness?

Oilbirds navigate through caves in complete darkness by using echolocation, a process in which they emit sound waves that reflect off objects to provide spatial orientation.123

Unlike the ultrasonic pulses used by bats, oilbirds produce rapidly pulsated clicks that fall within the range of human hearing, typically around 7,000 cycles per second. These clicks are emitted in bursts, sometimes reaching a frequency of up to 250 per second, allowing the birds to avoid obstacles and navigate their roosting and nesting sites within dark caves. While they rely on this acoustic system in the dark, oilbirds possess large, sensitive eyes and likely navigate visually when they fly outside of their caves at night to forage.123