www.daz3d.com has lots of birds for Poser and Daz Studio. But if you just want Poser for the birds, this might not be worth the money. Probably Daz Studio (which is free) is sufficient, but I'm not sure.

The big advantage of this solution, versus a native Vue solution, is variety and flexibility. Not only there are tons of different types of birds, but you can pose the birds individually to have more diversity.