Sierra learned how to whistle on Friday. She was trying to show me in the car on the way home from school, but I was trying to drive so I couldn't really see what she was doing. Every time I got a chance to glimpse back at her she had her mouth wide open, like she was trying to yawn, but a few seconds later I'd hear a whistle sound and I couldn't figure out how she was doing it with her mouth open so wide. Finally when we got home and was able to watch her I realized she was pursing her lips after doing the wide mouth thing. I think maybe she had yawned at some point and whistled by accident so she thought that was how you do it,just a guess. She's figured out now how to do it correctly, but I managed to get a video of her doing it the silly way before we showed her how to do it the right way