Ornithologists working in Oman say an owl discovered in a remote, mountainous region could be a new species.
Wildlife sound-recordist Magnus Robb told BBC News that he heard the bird's call whilst trying to record the call of another type of owl.
After repeated trips to the remote site, he and a colleague - naturalist and photographer Arnoud van den Berg - captured photographs of the bird.
They have published their observations in the journal Dutch Birding.
Mr Robb's first recordings of the bird's unfamiliar hoot were a serendipitous discovery in March of this year.
"I was listening through my headphones, when I suddenly heard something completely different [to the owl species I was there to record]," he told BBC News.
"I know the other Arabian owl sounds quite well, and this was clearly something that didn't fit."
The bird call expert said he had a "good inkling straight away that this could be something new".
"I even phoned a colleague a few minutes later and said, 'I think I've just discovered a new species of owl."