I've not voiced this here before - but that is dreadful! I can understand a small zoo, roadside or otherwise, any zoo, having domestic animals; but to mix them with wild spp in a what appears to be a smart, expensive exhibit is just not necessary. They could easily have made the effort to include some wild waterfowl and left the domestics in the children's farm where they would fit right in...
@Andrew Swales An image of the exhibit, as well as one of the turtles can be seen in the photo linked below taken by @snowleopard (Although since his picture was taken the turkeys have been removed). I didn't taken any photos of the exhibit.
In his photo, the building in the back of the exhibit is a part of the children's zoo, so the ducks are not wildly out of place. In addition, I didn't see any of the ducks or turtles myself. I've assumed this is only because of the weather we've been having recently, but it is possible they've discontinued the mix.
In my opinion, the zoo has other problems that need to be resolved before they should start worrying about the waterfowl in this exhibit.