"A little bird told me" is a way of indicating that you do not want to reveal who told you something. (Sometimes used playfully, when you think that the person you are addressing knows or can guess who was the source of your information.) Jill: Thank you for the beautiful present! How did you know I wanted a green silk scarf? Jane: A little bird told me. Bill: How did you find out it was my birthday? Jane: A little bird told me.