Cockatiel Whistling

Here's Rocky, once again, but he's singing this time! I have no clue what he's singing, perhaps his own song.
He started singing by me waving my drawing tablet pen around, that's what I was moving it towards him. [Normally when I hide it, he stops whistling to look for it]

He's almost 6 years old; He's a pearl-mutation cockatiel.

This video was mainly made for sound check and maybe to make some memories. :]

Camera: Canon PowerShot SX30 IS

Enjoy fellow bird lovers~!