I read a fascinating article in the August 17 edition of The New Yorker, about the small village of Kusköy, in Northern Turkey, where many inhabitants converse by whistling. Because the area is mountainous and in a dense forest, a whistle carries much farther than a shout.
Whistled languages have been known for centuries (not to me, however): Herodotus wrote of an Ethiopian “bat language” and another whistled language has been known in the Canary Islands (how appropriate) for over 600 years. They are also found in the Brazilian Amazon, in Northern Laos and in the Atlas Mountains of Morocco.
All whistled languages are based on spoken languages, with sounds made with the tongue, teeth and fingers. I am unable to provide a link to the article, but you should be able to find it at http://www.newyorker.com.(August 17, 2015) Three examples of the whistled language are given. All three sound pretty much the same to me, but apparently it works well in Kusköy, although the author notes that the bird language in this tiny village is not as prevalent as it once was. Because of nosy neighbors, residents are finding more privacy by texting.