I just got my new baby pekin duck today and i didn't see until now what is on his neck! I have no clue what it is and i'm scared. I already own 3 mallards, a blue and black sweedish and a magpie duck and have never seen this. Help!!!! it kind of bulges very little.
To me, it looks like something rubbed his down and skin off in that area. Perhaps he was continuously rubbing up against something. It's normal to bulge there because that's their crop where they store food.
I would rinse it off with mild saline solution or Vetericyn, just to prevent infection, and like desertdarlene said, keep an eye on it. Have you looked closely at the little dark flecks? What are those?