What Song is Chewie Singing?

Chewie is a 2-year-old cockatiel. His song sounded familiar, but I couldn't pin down what it might be. Frosty the budgie watched Chewie singing and provided a bit of backup now & then.

#cockatiel #budgies #singer #song ... https://www.youtube.com/watch?v=ES9ieRZkDSc