The "bird language" of Black Sea villagers in northern Turkey has been listed by UNESCO as being in need of urgent safeguarding.
Around 10,000 people, mostly in the district of Canakci in Giresun province, currently use and understand the language, according to UNESCO.
It was developed to allow people to communicate across steep mountain valleys but has been dying out as mobile phones reduce the need for new generations to learn the language.
Welcoming efforts to preserve it, Culture Minister Numan Kurtulmus tweeted: "Whistled language, also known as bird language, [which] echoed in the eastern Black Sea region for centuries, has been inscribed on the list of Intangible Cultural Heritage in Need of Urgent Safeguarding of UNESCO.
"I congratulate all my fellow Black Sea men who have kept this culture alive."
Today, the continued use of whistling is concentrated around the village of Kuskoy, which translates as bird village.
Until 50 years ago, it was being widely spoken around Trabzon, Rize, Ordu, Artvin and Bayburt but has now either disappeared entirely or is limited to a few words used by shepherds.
According to UNESCO, although the people of Canakci are aware of the importance of the language, technological developments and emigration have resulted in a "decline both in the number of people using the whistled language and areas where it is spoken".
"It is also clear that the new generations’ interest in whistled language has considerably diminished," the organization said.
"As a consequence, there is a risk that the element will gradually transform from its fundamental sphere of use and be torn apart from its natural environment, to become an entertainment-oriented, artificial practice."
Using whistles made with the fingers, tongue, teeth, lips and cheeks to simulate and articulate words, the language was developed in a way that showed a "strong indicator of human creativity", UNESCO said.
The practice is one of dozens of whistled languages used around the world where steep terrain or dense forests make communication difficult over distances, such as north Africa's Atlas mountains, the highlands of northern Laos or the Amazon basin in Brazil.
Since 1997, the Bird Language Festival has been held in Kuskoy to promote its use. The district has also provided training programs to primary school pupils for the last three years.
However, despite these efforts, UNESCO found that "the whistled language may soon totally disappear, unless essential safeguarding measures are undertaken using an integrated approach".