I'll share with you the critique I received when I posted my first shots of a bird, also a Cockatiel: always show the tail. Shoot vertically and make sure it's in the frame.
Otherwise, Dmitri looks very nice. A bit grumpy, though. My bird portraits have always been a little strange -- I really don't know what I'm doing with them which is a problem for me but the birds actually like me. Which means I don't have problems getting really cool poses. I just don't know which angles to shoot them from or what type of shots people are looking for.