I have a really nice muscovy drake and when I say really nice, you muscovy people out there will know that i actually mean grotesquely ugly. Well, maybe that's a bit harsh. Lets just say he is well carunckled. He is very healthy and I have a 1/4 ac pond which is also very healthy and clean. He bathes well, isn't sneezing, has no other symptoms. His eyes are so foamy, sometimes he has trouble seeing- as if the carunckles weren't bad enough for his eyesight. My ducks free range. I feed them a mix of scratch grains and black oil sunflower seeds. He seems to get the corn stuck in his throat sometimes and will go into a sneezing fit then, but the foaminess doesn't seem to coincide with his eating. It seems to be all the time. Could he have allergies?