Clickers

The wildlife refuge was demonstrating a couple of hawks, one of which wasn't entirely thrilled with being indoors out of her cage. But they'd been trained (injuries meant they'd never be released to the wild again), and she settled down. The trainer clicked a clicker on her belt when the bird calmed down.

Why a clicker?

I asked. Because different trainers had different voices. They wanted a consistent sound to indicate "Good job", and they settled on clickers.

The trainer still used words "Good bird," but that was probably for her and our benefit. The clicker was for the birds.