He can't stay quiet, he has a condition, if his mouth stops moving his brain stops working. Like now, he makes an indignant little noise upon being told to shut up, which is very mean! How could he say that!

Luckily the bird is a good distraction that interrupts whatever not-shutting-up thing he was about to snap back. His attention snaps to it once it comes to the ground, and he stares at it, a little transfixed. A real bird! Go figure.

After a long moment he hisses, not shutting up, "How do I get it to come here?"