If you mean flying Birds, it needs a lot of Work to make it possible. I don't think we will see it soon but maybe someday. I think there wasn't ever a Zoo-Game with a real flying System
If there are no birds in the game then what are Flamingos, Peafowls and Ostriches? Not saying we don't miss aviaries and actual flying birds, because we do, but to say we don't have any birds at all in the game isn't exactly true.