Sounds to me as if he's practicing his song. Usually only male cockatiels will sing a whistly tune, but with everything it takes practice. Soon he will sing a really lovely tune (the biggest part I miss about no longer keeping cockatiels).

If he's starting to sing then he's very happy

__________________

"Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat and no cat anywhere ever gave anyone a straight answer."

~The Paw Relations Blog~
~Nikki~
Owned by :-
Izzy - Congo African Grey
Missy - Galah Cockatoo
Shen - Black Labrador
Thomas, Charlie and Lola - Cats
Honey and Mustard - Rabbits
Gill and Rocket - Goldfish
~ Rest in Peace ~
Deedee - Timneh Grey 31.05.01 - 22.06.06