This is all personal taste, but here goes...
I personally like thematic scores, so maybe a theme and/or instrument for each character. I like the flute, very light and peaceful, but perhaps a short "stab" when the snake/lizard first appears for some contrast. Again, a personal choice, I would like to hear more "action" when dollying in to the tree. The score should become a little more menacing as the snake approaches and climbs the tree (get rid of the flute - it's no longer peaceful, it's getting dangerous) and vaguely martial when daddy bird picks up his spears. The snake isn't menacing enough as he begins his stalk. I'm not saying that you should Mickey Mouse everything (although perhaps more so than a live action piece, it is an animation after all...), but I think you should more strongly echo the emotions of each moment.
One thing that is not there is the sound design, so perhaps you should get in touch with him/her and find out what they are thinking and doing.
