I wonder if those two metal cages on the path are temporary (for construction worker safety) or permanent? If they are permanent, does this indicate the entrance and exit to a walk-in aviary?
My guess is the Aviary entrance. It matches up the the overhead rendering as the location of the Aviary. I also had the same thoughts while there. A few things made me feel they are intended as the Aviary entrance, most notably the position of the access points leading the person up or down the trail and the fact that the walkway juts up to the netting in only those two places and the obvious breaks in the railing. The railing would be present if these were temporary.
This may be late, but are does anyone know if there will be any other species than the bee-eaters and black-headed weavers? I've only seen bee-eaters and black-headed weavers for birds on the site.