As NZFanatic mentioned it is a topic often discussed, but since you mention birds of prey specifically then we can debate that. Everything stated above has been suggested, and while I'm completely against pre fabricated aviaries and exhibits, since it takes away the realism and possibilities that this great offers. A reduced amount radios for that bird to move around can definitely be a solution, since it seems not everyone is keep on the looping animations idea. Some Birds of Prey could have been added already, since they would not behave in very different way as the flamingos, and those are doing just fine in the game. Vultures as an example would be a much needed and exiting addition to our savanna exhibits, they could just hop and flight short distances similar to the Flamingos, most of the time they just rest over tree branches and other enrichment items. The Secretary Bird is an almost terrestrial bird of prey, and it is a crying shame that it was not released in the base game. I think there is no argument, that birds in general are frontier's biggest gap and weakness in the current game.
At this point however, it is my believe that the solution (one or the other) has already being found and they just need time to create all the models needed for a proper DLC. I honestly think nothing we say at this point will change what is to come, since they have been working on birds even before the base game came out, however it will be very interesting to see if they had to find some sort of compromise for these animations or if they will be added as a mixture of habitat animals and exhibit animals, who know really, but we need them. I do not believe that any upcoming DLC will change much from the current format, so we might have to keep on waiting for birds, since they will definitely 100% not be a regular DLC but a full on expansion.