I should've clarified. It's on the 2-disc special edition release. There's a 2nd disc with all the behind-the-scenes stuff, actor interviews, etc. Here's a taste but unfortunately not related to the...

http://www.3dtotal.com/ffa/tutorials/maya/bird_tutorial/bird.asp modeling
http://www.highend3d.com/maya/downloads/mel_scripts/dynamics/Feather-System-4832.html feather system

IIRC, I believe...