My young drake Hunter has a swollen head. I was out with the ducks for a few hours this evening, towards end of time I started noticing one side of Hunter's head seemed a little lopsided. As I was herding them into the night pen it struck me that Hunter's head was really swollen. I picked him up and felt the area, it feels like a deflated balloon. It doesn't feel like fluid or tight like inflamed tissue. It feels and acts like air, I can see where the skin around his eye is also inflated. That exactly what it feels like, inflated. He is acting normally, eating and pooping. upset about being picked up and messed with but not acting sick. What could this be? I looked up swollen head posts, maybe get a sulfa type med in case of infection? He has no drainage, no wheezing or respiratory type symptoms. It looks really odd. He has been a very healthy duck and no health issues to date other than this. I tried to get a picture but hard to do it one handed with wiggling duck on my lap. Any ideas on what this could be?