They found a report mentioning the Rinjani Scops owl's tone, which differs from the barking cry of the Moluccan Scops owl.

NPR: Brown-And-White Whistling Owl ID'd As New Species

They noticed that its whistled note was entirely different from other songs, including that of the widespread Moluccan Scops owl, or Otus magicus.

NPR: Brown-And-White Whistling Owl ID'd As New Species

But scientists from Sweden and the U.S., who were visiting the island doing separate research on another nocturnal bird, both recorded the Rinjani Scops owl's vocalizations.

NPR: Brown-And-White Whistling Owl ID'd As New Species

Lombok also remained less visited by bird researchers than other parts of Indonesia, which may explain why it took longer for the Rinjani Scops owl to be identified.

NPR: Brown-And-White Whistling Owl ID'd As New Species

The Rinjani Scops owl was first identified in 2003 and has since been spotted only on Lombok island, about 25 kilometers (15 miles) from the popular resort island of Bali.

NPR: Brown-And-White Whistling Owl ID'd As New Species