
Good little boys shouldn't be wondering away from the group to follow after a glimpse of something. Normally Zuko was a good boy, followed directions, watched out for his siblings, and so forth. But he was bored, they weren't moving anyway for a little while and most of his siblings were taking a nap, or at least trying to, last he saw so he slipped away and into some bushes.
He figured one of the adults saw him since he wasn't very good at stealth, yet as he was working on it, but didn't check to make sure. He had something to hunt down after all!