Nuttopia

While I'm thinking of it, I'm not sure if any of the artists I talk to personally could do the art you're looking to commission, but I've seen some work by this person - http://www.creaturespot.com/main/author/brynnmetheny
That looks like the sort of thing you want.
Specifically this - http://www.creaturespot.com/display/ShowImage?imageUrl=/storage/post-images/dino_lineup.jpg?__SQUARESPACE_CACHEVERSION=1276710139763
It's feathered dinos in various outfits rather than birds but you get that kind of feel from them.
I don't know this person myself but it's worth shooting them an email.