In the rugged crags of Barranco de Ávalo, a ravine on the small Canary Island of La Gomera, two local 12-year-olds were practicing their Silbo Gomero, the local whistling language. For an entrancing few minutes, Irún Castillo Perdomo and Angel Manuel Garcia Herrera's lilting warbles reverberated around the barren gorge and soared proudly into the air like eagles in flight.

50 Reasons to Love the World - 2021

Why do you love the world?

"Because the whistle is an inheritance from our ancestors and maintaining it identifies us as Gomeros." – Eugenio Darias, teacher

More Reasons to Love the World

They were accompanied by 70-year-old retired Silbo Gomero teacher Eugenio Darias, whose grandfather used to own and work on this very same land. He told me that the boys' whistled conversation was similar to any they would have over text message or in the playground, but the focus was instead on the six differentiating sounds that make up La Gomera's protected whistle language.

While it's true that most children their age would sooner pick up their phone and tap away, this small Canary Island invites them to think differently. Thanks to Darias, their threatened tongue has been a compulsory school subject since 1999 – and almost all 22,000 residents can understand it alongside their mother tongue of Canarian Spanish.

"It's important to give students the idea that they can really use it if they need to, like other languages, but also that it's not necessary for everyday use," said Darias, who pioneered the Silbo Gomero learning programme. "Our aim is to give the whistle more importance so that the children can be confident using it together. Importantly, having the whistle protected within our compulsory curriculum prevents extinction altogether."

Whistle languages, in varying guises, exist in as many as "70 places", according to local broadcast journalist Francisca Gonzalez Santana. "In Turkey, for example, the whistle began 500 years ago during the Ottoman Empire," she said. "It then spread to all regions of the Black Sea; and in Mexico, we can still find whistled communication in Spanish – Chinantec ."

Silbo Gomero, which is one of the most studied whistling languages and was officially declared an Intangible Cultural Heritage by Unesco in 2009, uses six condensed sounds to communicate. Two differentiating whistles replace the five spoken vowels in Spanish, while just four replace the 22 consonants. Whistlers elongate or shorten the sounds to mimic the words.

Silbo Gomero is perfectly suited to this landscape of deep valleys and steep ravines (Credit: Richard Franks)

Several whistling methods exist on the island, though perhaps the most traditional is demonstrated by local sculptor José Darías. His Whistling Tree sculpture at Mirador de Igualero, a viewpoint in Vallehermoso overlooking a ravine where Silbo Gomero was most active, shows how the index finger should be bent and placed inside the mouth while whistling with an open palm beside it to amplify the sound.

Experienced whistlers use different finger methods and can often tell who is calling by the whistle's "accent" alone – but most whistlers will introduce themselves and call the recipient's name. When the message is understood, they whistle back " bueno bueno ". Short and simple indeed.

What isn't quite as short and simple is the language's origin. History books suggest the whistle dates back to at least 1402 during the initial Spanish conquest of the Canary Islands, but Silbo Gomero's earlier heritage is often up for debate.

You may also be interested in: • The world's most endangered sound? • Greece's disappearing whistled language • The indigenous recipe for living well

DNA-based research published in 2019 by Tenerife's La Laguna University has matched La Gomera's early inhabitants, the Guanches , with Berbers (now known locally as Amazigh). These indigenous people roamed North African regions more than 3,000 years ago and communicated by whistle ; it's therefore widely believed that the Spanish settlers on the island adapted the whistling language of La Gomera's early inhabitants to suit their native tongue.

La Gomera's specific whistle found its way to other Canary Islands during the three-year Spanish conquest – it even later followed emigrating Gomeros to South America – but it only survived in one other island in the Canaries: El Hierro, where, according to Santana, the whistle is still occasionally used among elderly residents.

Eugenio Darias pioneered the Silbo Gomero school learning programme in 1999 (Credit: Richard Franks)

Silbo Gomero lent itself to La Gomera's demanding terrain – namely its deep ravines – allowing the locals to communicate with a drifting, piercing sound that could travel for several kilometres. From atop the ravines, the locals would announce events, request livestock be brought over, warn of impending danger, or even announce the death of a family member. "It saved a lot of climbing," said Darias.

In the 1950s, Silbo Gomero was used so frequently that there was often a scattered queue of farmers waiting to send instructions across the valleys. "It was difficult terrain to work on – nobody wanted to climb up and down the ravines to pass on a message. Because of this, so many whistling conversations were happening at the same time, and we would have to wait our turn," Darias said.

"It was like traffic!" he continued. "However – during the 1960 and '70s, most agricultural land was abandoned and many of the workers had left the island. As Silbo Gomero was mostly used between local livestock holders, when they left the island, the whistling left with them too."

BBC Travel · Eugenio Darias demonstrates how to whistle Silbo Gomero

Silbo Gomero was first in decline by the 1960s, when growing economic conditions forced many of the island's workers to emigrate to more prosperous countries like Cuba and Venezuela, as well as the neighbouring Canary Island of Tenerife. Soon after, phones became commonplace and threatened the language altogether.

By the 1990s, modern technology ascendancy and the introduction of new roads and paths on La Gomera removed the necessity and practicality of Silbo Gomero, dangling it near extinction. This is where Darias stepped in to protect its future by ensuring future generations not only understood the whistle but were able to use it too.

The Whistling Tree sculpture at Mirador de Igualero demonstrates the whistling technique (Credit: Richard Franks)

“The whistle has been defended with greater care in the Canary Islands," Santana noted, “because it is an essential part of our culture: the orography of the islands, with mountain areas and canyons, and our economy that has been linked to agriculture and livestock."

While the whistle is now rarely heard outside of school or other official programmes, however, it is occasionally used in the few parts of the island with no telephone connection. "I know of two goat herders who still whistle to each other," Darias said. "They are nephews who live on the south side of the island. Their livestock moves around in an area with no mobile network, and that's why it's necessary for them to use it."

"Would you use Silbo Gomero today if your phone ran out of battery?" I asked.

"Of course!" he said. "After all, we'd still communicate that way if phones didn't exist."

BBC Travel celebrates 50 Reasons to Love the World in 2021, through the inspiration of well-known voices as well as unsung heroes in local communities around the globe.

---

Join more than three million BBC Travel fans by liking us on Facebook , or follow us on Twitter and Instagram .

If you liked this story, sign up for the weekly bbc.com features newsletter called "The Essential List". A handpicked selection of stories from BBC Future, Culture, Worklife and Travel, delivered to your inbox every Friday.