ProAnimator's really great at what it does, but it's probably not your best choice for this sort of action. You're better suited using an app that offers the ability to parent objects to eachother, establish IK chains and the like. One inexpensive alternative might be Poser. I've seen some animated birds in flight and models from Daz3D. You can buy pre-made flight motions from Daz as well. They aren't as easy to create as you might think. Otherwise, Lightwave, Cinema, Maya, but those are in a whole different price and learning curve league.
I assumed as much - many years ago I started working with 3D Studio and have an old copy around here somewhere - I might try to mess around with that. Although, and I did look at the site mentioned above, thank you, is there other 3D sites around that may have animated elements for sale? I need a few things to add into a video project that I am working on.