Observation for whistling

I have a little one who is 35 months old and has been trying desperately to whistle for weeks! Today she came in and she has mastered it! She was so proud...but I’m stumped as to where I can link the observation too.
Or shall I just record it as a wow moment?

It is definately a great example for characteristics of effective learning under the active learning area.

‘ active learning - children concentrate and keep on trying if they encounter difficulties, and enjoy achievements‘.