Over the last 2 weeks, I noticed that my drake cayuga has a very fat chest sometimes. I have picked him up many times to make sure he isn't going to die but it always goes away. No hardness, no lumps, no abnormalities. It is not always fat, it does go away and come back. I was watching them today and it came and went a few times within about 10 minutes.
I believe that it is his way of showing off but I can't find any literature that backs me up. Others think he is deformed.
Thoughts?
Here is a photo with it

I believe that it is his way of showing off but I can't find any literature that backs me up. Others think he is deformed.
Thoughts?
Here is a photo with it