He starts walking in a direction which looks like it leads down. (He didn't climb up, so he's guessing.) The shade-dish-machine-thing follows conveniently overhead, and for some reason there's a snail's-trail of glass rippling along the surface of the rocks that seems to be keeping to a rough circle around them.

“Glass is really easy to claim, and it's transparent unless you add something to it, and it makes really tough things with a bit of reinforcement, so it's useful for a lot of things. Metal is easy too but expensive, and you use it when you need it, like that electric circuit. Really, any time you need more than a particular shape, you might need something other than glass.”

The bird-bodies take off in other directions.