If the exhibit is unattractive to the birds it should be fine, but I would still go for the BZ's Caiman option (Separating the exhibit with hidden nets)
A little diagram showing the exhibit design of Burgers' Zoo's caiman enclosure:
Visitors enter through a rock tunnel, the birds are scared of the dark and won't fly through (you can also use plastic flaps to stop the birds). On top of the tunnel is a net that separates the corner, hidden by foliage. The enclosure in the separated area is mostly barren, but there is plenty of foliage in the top area. In the case of BZ, the separated area is only separated to larger birds. To prevent the ducks and ibises from swimming here, the smaller passerines can still come here, because they have no interest in the barren enclosure. BZ uses a lot of vines and strangling plants on the edges of the exhibit to hide the fact that it is barren, to still give it a natural look.
Caiman area in BZ:
Walkway (You can see the net in the background)
Caiman exhibit (Seems lush, but the ground is barren)
The less disguised part of the separation net (Doesn't really break immersion if that's what you're going for)
The underwater viewing area is in the bird area, you can again see the net above it