My 9 year old girl is a whistler. She started when she was 3, and now is 9 and started her vibrato about a year ago. I couldn't believe it when she started vibrato. She has no training, but I am a vocal music teacher so I can work on phrasing and breath control a bit. We are looking for some good solos for her to listen to and learn on her headphones on the bus. Thanks for posting this. I will search for the MP3 download. I will keep looking for other fun ones for her.
As a kid when I went grocery shopping with my mom, if we got separated I could always find her by listening for her happy whistle to the Muzak in the store. She didn't do it on purpose and she couldn't whistle like this, but still it's a pleasant memory.