My first 2 thoughts would be that he likes getting a reaction out of you or has made it a game to make you pick the food up, and/or he's not hungry. Different solutions, obviously to which it might be.
How much milk is he drinking? How are his portion sizes? Many lo's have a decrease in appetite after turning 1 yr because their growth slows down, and they don't need as much milk because they are starting to need the variety of nutrition in the solids.
And how long has he been doing this? If it just started the last couple of days he could be teething or have a cold, etc.
HTH!