In Colegio de Agulo, in the north of the Canary Island of La Gomera, teacher Lino Rodriguez Martin inserts his index finger into the side of his mouth, doubles back his tongue and emits a long whistle of varying pitch. Fifteen-year-old Sylvia smiles, raises her hand to her mouth and whistles to her classmate on the other side of the room, who promptly stands up. Gradually the whole class is drawn into an increasingly sophisticated birdsong-like conversation that is as unintelligible as it is enchanting to an outsider.
They are communicating in their ancient tongue El Silbo, one of the most complex whistling languages in the world. Today, June 15, is El Silbo day, and whistling has been on the school curriculum for a year.
Several pupils are having trouble whistling with only one hand. The second hand is traditionally used like a horn to make the sound more powerful. This is too loud for the classroom and Se$or Martin keeps having to indicate that they should put their other hand down. Some children have picked up the habit of using both hands from their grandparents, who traditionally used the language to communicate across the exceptionally high number of deep valleys on this volcanic island. By using this technique islanders can talk to neighbours, who might be three kilometres or more away, without picking up the phone.
"When I was younger there was no alternative means of communication," says Sr Martin, 57. "The mountains were often covered in mist and if I wanted to talk with other members of my family the only way to do it was by whistling." Many islanders at that time spent their days working alone, growing fruit or tending goats. The community had no church and when there was a death, for example, the news and details of the funeral would be transmitted using El Silbo. They also used El Silbo to control their dogs. "We would often spend more time in the day communicating in El Silbo than in Spanish," Sr Martin says.
The struggle to get the traditional language on the curriculum and have it recognised as a serious and important part of the Canary Islands' cultural history has been a long one. It was neglected in the Fifties and Sixties as part of Franco's policy of repressing regional languages to promote national unity. Stories abound from that time of islanders running rings around officials from mainland Spain by whistling warning of their arrival to young men evading military service or dodging taxes. The visitors inevitably went away perplexed.
As communications improved on La Gomera, with better roads, telephones and later mobile phones, a generation of speakers lost the art of whistling and El Silbo faced extinction. Sr Martin and his colleague, Isidro Ortiz Mendoza, 68, recognised what was happening, and with support from parent-teacher associations toured schools to encourage children to learn to whistle during playtime.
They found that girls were more receptive than boys, who preferred football. The two teachers lobbied politicians, arguing that El Silbo was part of the island's heritage.As others joined the campaign to make El Silbo part of the syllabus, it was discovered that the oldest known document from the Canary Islands contained a reference to the language. The pre-Hispanic script, dated 1413, records that "Gomera is inhabited by many people that speak the strangest language of all... because they speak with fat lips as if they had no tongue".
"The campaign received a big boost as the result of a beer advertisement," says Ramon Correa, 35, co-ordinator of the El Silbo campaign. "In 1997 the manufacturer Tropical used a TV commercial in which customers were crowded around a bar noisily trying to attract the harassed barman's attention when one customer stuns those waiting and jumps the queue with a perfectly whistled order."
The advertisement provoked widespread interest across the islands and in June 1998 the Canarian parliament set up a commission under Professor Ramon Trujillo Carre$o, dean of Spanish language at the University of La Laguna, Tenerife, to explore the possibility of introducing the language into the curriculum of La Gomera as part of the study of language and literature. The following year it was made obligatory for the 1,087 primary schoolchildren and optional for the 395 secondary students on the island.
El Silbo has no syntax or grammar of its own: it is a sign language, like Morse code. Professor Trujillo found that speakers manipulate only two vowels and four consonants. Although some say this restricts conversation, expert whistlers insist that if you can say it, you can whistle it.
Children's progress this year has been monitored by continuous assessment. Pupils have had to demonstrate their understanding of the language by responding when their names are whistled, writing whistled messages in Spanish in their notebooks and passing on messages to other children.
At the most basic level, children are required to learn everyday words and phrases and answer simple questions. Messages must be whistled with clarity, power and rhythm.
Has anyone failed to whistle to the required standard? "Not this year," says Sr Martin. "The curriculum is still developing and we are in the process of clarifying levels. We also need to get the teaching standard right, which is why more than 60 teachers from all over the island have been attending a training course. Not everyone can reach the standard but generally it's going very well."
The campaigners' success goes against the trend of disappearing languages. a report in Science magazine in May predicted that at least half, and probably nearer three-quarters, of the world's languages will vanish by 2100 as a result of the growing dominance of English, Spanish and Mandarin.
The blunt message of the report is that many languages such as El Silbo will only be saved temporarily and that Sres Martin and Mendoza and their colleagues are whistling in the wind.
But the El Silbo teachers remain unperturbed. They point to positive signs, such as the fact that young people are using their whistling skills to meet and chat up pupils from other schools, and that in the future they will be able to earn a living in schools teaching El Silbo. "Now everyone here is learning it," Sr Martin says, "It will survive."