Children can be so funny

I usually say hello or wave to children when I see them. It's kind of fun to see their reactions. Sometimes they'll stop misbehaving at the novelty of a stranger saying something. So today I'm shopping and I hear this whistling, I get around the corner and was surprised to see this young boy in a grocery cart basket. I commented "You are a very good whistler", his mother said "He can whistle at girls too". Just then, this little boy let's out a perfect cat call whistle. I was stunned. I commented, "Wow, he could get a guy in trouble, n0 girl would believe he did that". His mother and I laughed. Later it dawned on me, where did he learn to do that?