It is a Mystery!

Me: "Why does a grown man (a pensioner, no less) buy a pack of 10 square colouring pencils?"
Him: "To give his grandaughter?"
Me: "No."
Him: "I can't imagine."
Me: "Well, it is because he has always wanted to take a photograph of their ends!"
Him: "Pardon?"
Me: "You heard!"
Him: "Okay, so now you have done it do you fell better?"
Me: "I feel wonderful!"
Him: "What next?"
Me: "I want to take a photograph of a ........... woodpecker!"