One duckling in particular tends to vibrate its bill, working at my hand then going up my arm. At first I thought it might have been affection, but today I was moving things around in their pen, and moved my hand slowly over to touch them, and all of a sudden out of the group shot out a duckling right at my hand and started doing this bill vibrating thing, almost as if it were a defense or was threatened. My wife tends to think it's only because they're looking for food. Any thoughts?
