"You're, um, hardly the first person I've met with wings. But never anyone powerful enough to stay airborne constantly."

Giles can't help but wince in sympathy as her wing catches, but he's not sure what he could do to help it and so makes no move to climb up the tree. He's probably just overload it anyway, or else attract more vengeful birds. He does call up: "Are you all right?" though. Just to be safe.