Tumble is good. Let's put Sense Motive in for Survival. I think geography might be useful for knowing where evil tribes, etc, are. This thing has to travel a lot.
Quick question: the effects of a storm of vengeance are cumulative, right? So the 3rd round effect occurs also in the 4th-10th rounds?
Feats: Flyby Attack, Hover, Cleave, Multiattack, Power Attack, Snatch, Ability Focus (Surrounding Storm), Penetrate Damage Reduction (silver), Penetrate Damage Reduction (cold iron), Aligned Attack, Improved Flyby Attack, Great Cleave, Weapon Focus (talons), Improved Critical (talons), Overwhelming Critical (talons)
Instead of the Cleave, Great Cleave, WF, IC, OC chain, I could also see going to Epic Will, Imp Bull Rush, Awesome Blow, Leadership, Epic Leadership. I picked Penetrate DR twice and Aligned Attack (even though it's psionic) because the Thunder Bird fights summoned critters a lot, probably including demons and devils.