"Have you noticed that?
He whistles when he's about his work, and then he has a calling whistle that nearly all of the animals know, and the men run when they hear it.

You'd see every cow in this stable turn its head, if he whistled in a certain way outside.

He says that he got into the way of doing it when he was a boy and went for his father's cows.

He trained them so that he'd just stand in the pasture and whistle, and they'd come to him.

I believe the first thing that inclined me to him was his clear, happy whistle.